ETV6-NTRK3 Fusion Research Articles

Secretory carcinoma of major and minor salivary glands with ETV6-NTRK3 gene fusion: overcoming misdiagnosis in the era of tumour-agnostic therapy with TRK inhibitors.

Secretory carcinoma (SC) of the salivary gland is an extraordinarily rare tumour. Accurate diagnosis of SC is crucial for understanding the clinical course, prognosis, and selection of optimal therapy. The aim of this research was to analyse retrospectively the clinical and pathological characteristics of patients diagnosed with SC of the salivary gland from 2017 onwards, which aligns with its addition to the World Health Organization classification. We conducted a retrospective, single-centre, clinicopathological analysis of patients diagnosed with SC of the salivary gland between 2017 and 2022. The analysis included the evaluation of NTRK3 gene rearrangements and immunohistochemical (IHC) profiling. The study included 6 patients, comprising 4 women and 2 men. The average age of the patients was 50 years (standard deviation 26). Three cases presented with tumours in the parotid gland, while one case each involved the submandibular gland, sinonasal tract, and buccal mucosa. Interestingly, despite the characteristic IHC profile, each case was initially diagnosed as a different type of salivary gland cancer. Next-generation sequencing analysis was performed in 3 cases, revealing the presence of the ETV6-NTRK3 fusion gene. This cohort notably features an intriguing case: the youngest patient documented in literature, distinguished by extended follow-up and delayed recurrence. In summary, emphasizing the risk of misdiagnosis is pivotal in the context of SC of the salivary gland, which can manifest across diverse glandular sites. Accurate diagnosis, underscored by the assessment of NTRK3 gene rearrangements, assumes a critical role in guiding effective management and treatment decisions.

Clinicopathological features and genomic profiles of a group of secretory breast carcinomas in which progressive cases have more complex genomic features

BackgroundSecretory breast carcinoma (SBC) is a rare malignant breast neoplasm with distinct histological features, including solid, microcystic, tubular, and rarely papillary structures, traditionally characterized by a t (12;15) (p13:q25) translocation, which usually leads to ETV6-NTRK3 fusion, suggesting an early event in tumorigenesis. Due to the rarity of this disease, very few genome sequencing studies have been performed on a series of cases, especially progressive cases.MethodsSeven lesions from 5 patients diagnosed at the Third Affiliated Hospital of Soochow University from 2007 to 2021 were included. Clinicopathological features and prognosis/survival data were collected. Next-generation DNA sequencing was performed on six of the seven lesions.ResultsIn total, 3/7 (42.9%) lesions demonstrated estrogen receptor (ER) expression, including weak, moderate to strong staining, and no lesion demonstrated progesterone receptor (PR) expression. There were no cases of human epidermal growth factor (HER2) overexpression, and the Ki-67 index was low. S-100 and pan-TRK protein were diffusely positively expressed in all cases. All lesions were characterized by a t(12;15) (p13:q25) translocation, leading to ETV6-NTRK3 fusion confirmed by fluorescence in situ hybridization (FISH). The sequencing results showed that ETV6-NTRK3 fusion was the main driver of early tumorigenesis, while SBC with invasive biological behavior had more complex genomic variation in which TERT promoter mutation was detected.ConclusionsImmunohistochemical staining of a biomarker panel, including ER, PR, HER2, Ki-67, S-100 and pan-TRK, can be used as an auxiliary diagnostic tool, and FISH detection can be used as a diagnostic tool. ETV6-NTRK3 gene fusion involving multiple sites may drive tumorigenesis, while mutations in the TERT promoter region may be a factor driving tumor progression.

GISTs with NTRK Gene Fusions: A Clinicopathological, Immunophenotypic, and Molecular Study.

The most common mutations in gastrointestinal stromal tumors (GISTs) are KIT or PDGFRA mutations. Recently, neurotrophic tyrosine receptor kinase (NTRK) fusions have been reported in WT GISTs, which increased interest in introducing tropomyosin receptor kinase (TRK) inhibitors as treatments for GISTs with NTRK fusions. Hence, we aimed to screen NTRK fusions in WT GISTs; we used fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), and immunohistochemistry (IHC) to screen NTRK fusions in 46 WT GISTs and evaluate each method. We further reviewed NTRK fusion-positive GISTs from the literature and performed clinical and pathological analyses; two GISTs with an ETV6-NTRK3 fusion (5%) were identified, while only one (50%) was positive for Pan-TRK expression. On the other hand, among the six GISTs with Pan-TRK-positive expression, only one (17%) harbored NTRK fusion. The literature review revealed the strong consistency between FISH and NGS and the limited value of Pan-TRK IHC in screening NTRK fusions in GISTs. In addition, the clinical and pathological analysis showed that GISTs with NTRK rearrangement occurred less frequently in the stomach, were more frequently larger in size, and the epithelioid type presented with a higher risk of recurrence. The NTRK3 fusion has been more common than the NTRK1 fusion in GISTs to date; our study identified two ETV6-NTRK3 fusions in 46 WT GISTs. Compared with FISH and IHC, NGS is preferred for screening WT GISTs, including NTRK rearrangements. However, since GISTs with NTRK fusions are rare, further studies including more samples and mechanistic investigations should be conducted in the future.

Congenital mesoblastic nephroma: review of current management and outcomes in a single centre.

Congenital mesoblastic nephroma (CMN) is a rare tumour of the kidney with an overall excellent prognosis. Once considered a benign tumour, it is now recognized to carry a risk of recurrence and metastases with subsequent poor outcomes. The potential for genetic aberrations such as ETV6-NTRK3 fusion raises the potential for targeted treatments in certain patients. The optimum mode and frequency of surveillance is unclear. This study aims to assess this institution's experience with CMN and long-term outcomes. A single centre retrospective review was performed of all confirmed cases of CMN between October 2001 and January 2021. Nine cases of CMN in patients under 12 months of age were identified. The histopathology, management and outcomes of these patients are discussed. CMN overall has a very good prognosis, but a subgroup does exist that will have poor outcomes. It is difficult to accurately identify this group to target adjuvant therapy.

Clinicopathological observation of 10 cases of salivary secretory carcinoma

Objective: To investigate the clinical and pathological features of salivary secretory carcinoma (SSC). Methods: Ten cases of SSC confirmed in the Department of Pathology,Capital Medical University School of Stomatology from January 2014 to December 2021 were retrospectively included, including 5 males and 5 females, with a median age of 46.5 years. The microscopic morphology, immunophenotype, special staining and clinical follow-up of 10 cases of salivary secretory carcinoma were observed. Ten patients were tested with S-100, vimentin, mammaglobin, Dog-1, p63 and Ki-67, 9 cases with cytokeratin (CK) 8/18, 8 with CK7, 6 with calponin, 5 with smooth muscle actin (SMA) and GCDFP15, 4 with CK5/6 and 1 with SOX10. The ETV6-NTRK3 fusion gene was detected by fluorescence in situ hybridization. Results: Seven of the 10 SSC were located in the parotid gland and 3 were located in the cheeks. Histomorphology showed solid, papillary-cystic, follicular, microcystic, and macrocystic types. In 7 cases, tumor cells were dominated by single arrangement type, while certain mixed arrangements existed in some areas. The cytoplasm of the tumor cells was rich in eosinophilic, fine granular or vacuolar shapes, and clear cytoplasm was seen in 2 cases. The nuclei were mostly oval-shaped vesicular nuclei, with nucleoli in the center. Immunohistochemistry showed CK7 (8/8) positive, CK8/18 (9/9) positive, S-100 (10/10) positive, vimentin (5/10) positive, (4/10) partially positive and (1/10) less partially positive, mammaglobin (7/10) positive, (1/10) partially positive and (2/10) some individual cells positive, Dog-1 (10/10) negative, CK5/6 (4/4) negative, p63 (7/10) negative and (3/10) partially positive, SMA (5/5) negative, calponin (6/6) negative, and Ki-67 index was 5%-20%. Secretions of 5 cases showed periodic acid-Schiff (PAS) and PAS with diastase (PAS-D) staining positive. All 10 cases showed ETV6-NTRK3 fusion positive. Six cases were successfully followed up for 32-91 months, of which 2 cases recurred after 28 and 74 months and underwent surgical resection again. All cases followed up are alive and disease-free. Conclusions: The salivary secretory carcinoma is a rare low-grade malignant tumor. In certain cases, morphology is atypical and mammaglobin is immunohistochemically positive in only individual tumor cells. Therefore, the diagnosis should be supported with morphology, immunohistochemical staining, and molecular feature preferably.

222O Updated efficacy and safety of larotrectinib in patients with TRK fusion salivary gland tumours

Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are oncogenic drivers of various tumour types, including salivary gland tumours (SGTs). Secretory carcinoma of the salivary gland, a rare subset of SGTs, is characterised by an ETV6-NTRK3 gene fusion found in ≥80% of cases. Larotrectinib is a highly selective, central nervous system-active, tropomyosin receptor kinase (TRK) inhibitor with an objective response rate (ORR) of 92% across 24 evaluable patients (pts) with a variety of SGTs, as of July 2020 (Le et al.

Secretory carcinoma of the sinonasal cavity and pharynx: A retrospective analysis of four cases and literature review

Secretory carcinoma (SC) is a recently recognized type of salivary gland tumor characterized by t(12;15) (p13;q25) translocation resulting in an ETV6-NTRK3 gene fusion. Most SCs are located in a main salivary gland, and primary sinonasal secretary carcinoma is rare. We describe three cases of primary SC in the sinonasal cavity with high-grade transformation (HGT) in one case, and the first case in the pharynx. All tumors comprised slightly atypical cells with solid, tubular, microcystic growth patterns. The case with HGT included two components with distinct sharp boundaries and comedo necrosis, high mitotic figures and obvious cellular atypia. Tumor cells were positive for vimentin, S100, and Gata-3 and negative for p63 and DOG-1. Three cases showed nuclear staining of pan-TRK and one showed cytoplasmic staining. All cases harbored ETV6 gene rearrangement, and ETV6-NTRK3 gene fusion was detected in three cases. Most patients were treated with radical resection and adjuvant therapy. After excision, all remained tumor-free for 65–164 months (medium 98.5 months). SC in the sinonasal cavity and pharynx is a low-grade malignant tumor with histologic features overlapping those of other salivary gland tumors. Immunohistochemical analysis and fluorescence in situ hybridization are useful techniques for its differential diagnosis.

Prevalence of NTRK Fusions in Canadian Solid Tumour Cancer Patients.

IntroductionNeurotrophic tyrosine receptor kinase (NTRK) gene fusions occur in ~ 0.3% of all solid tumours but are enriched in some rare tumour types. Tropomyosin receptor kinase (TRK) inhibitors larotrectinib and entrectinib are approved as tumour-agnostic therapies for solid tumours harbouring NTRK fusions.MethodsThis study investigated the prevalence of NTRK fusions in Canadian patients and also aimed to help guide NTRK testing paradigms through analysis of data reported from a national clinical diagnostic testing program between September 2019 and July 2021.ResultsOf 1,687 patients included in the final analysis, NTRK fusions were detected in 0.71% (n = 12) of patients representing salivary gland carcinoma (n = 3), soft tissue sarcoma (n = 3), CNS (n = 3), and one in each of melanoma, lung, and colorectal cancer. All three salivary gland carcinomas contained ETV6-NTRK3 fusions. Thirteen (0.77%) clinically actionable incidental findings were also detected. Two of the 13 samples containing incidental findings were NTRK fusion-positive (GFOD1-NTRK2, FGFR3-TACC3 in a glioblastoma and AFAP1-NTRK2, BRAF c.1799T>A in a glioma). The testing algorithm screened most patient samples via pan-TRK immunohistochemistry (IHC), whereas samples from the central nervous system (CNS), pathognomonic cancers, and confirmed/ putative NTRK fusion-positive samples identified under research protocols were reflexed straight to next-generation sequencing (NGS).ConclusionThese findings highlight the benefit and practicality of a diagnostic testing program to identify patients suitable for tumour-agnostic TRK inhibitor therapies, as well as other targeted therapies, due to clinically actionable incidental findings identified. Collectively, these findings may inform future guidance on selecting the appropriate testing approach per tumour type and on optimal NTRK testing algorithms.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40291-022-00617-y.

667P Updated efficacy and safety of larotrectinib in patients with TRK fusion salivary gland tumours

Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are oncogenic drivers of various tumour types, including salivary gland tumours (SGTs). Secretory carcinoma of the salivary gland, a rare subset of SGTs, is characterised by an ETV6-NTRK3 gene fusion found in ≥80% of cases. Larotrectinib is a highly selective, central nervous system-active, tropomyosin receptor kinase (TRK) inhibitor with an objective response rate (ORR) of 92% across 24 evaluable patients (pts) with a variety of SGTs, as of July 2020 (Le et al. Oncologist 2022 [in press]). We report updated efficacy and safety of larotrectinib in pts with TRK fusion SGTs with longer follow-up. Pts with TRK fusion SGTs were identified from two larotrectinib clinical trials (NCT02122913, NCT02576431). Pts received larotrectinib 100 mg twice a day (BID) except for one pt who received 150 mg BID in the phase 1 trial (NCT02122913). Response was assessed by independent review committee (per Response Evaluation Criteria in Solid Tumours v1.1). As of July 2021, 25 pts with TRK fusion SGTs were identified, including 24 with an additional year of follow-up. Median age was 59.0 years (range 28–80). All pts had ETV6-NTRK3 gene fusions. ORR was 84% (95% CI 64–95%): 8 complete responses, 13 partial responses, 2 stable disease and 2 progressive disease. Median time to response was 1.8 months. Median duration of response (DoR) was not reached; median follow-up was 39.6 months. Median progression-free survival (PFS) was 56.0 months (95% CI 30.8–not estimable) at a median follow-up of 41.3 months. Median overall survival (OS) was not reached at a median follow-up of 43.7 months. The 36-month DoR, PFS, and OS rates were 71%, 64%, and 82%. Duration of treatment ranged from 1.0 to 68.0 months. At data cut-off, 8 pts had progressed, with 5 pts continuing treatment post-progression for ≥4 weeks. Treatment-related adverse events (TRAEs) were mostly Grade 1–2. Grade 3–4 TRAEs were reported in 6 pts (24%). There were no treatment discontinuations due to TRAEs. Larotrectinib demonstrated rapid and durable efficacy with a favourable safety profile in pts with TRK fusion SGTs. These data highlight the importance of identifying NTRK gene fusions in pts with SGTs.

Secretory Carcinoma of the Breast Mimicking Invasive Ductal Carcinoma: A Case Report

Patient: Female, 40-year-old Final Diagnosis: Secretory breast carcinoma Symptoms: Breast mass Medication:— Clinical Procedure: — Specialty: Oncology Objective: Rare disease Background:Secretory breast carcinoma (SBC), an extremely rare malignancy, is related to a chromosomal translocation which leads to an ETV6-NTRK3 fusion mutation. SBC is characterized by eosinophilic secretions and is usually triple-negative, with a small number of patients demonstrating ER-positivity of the tumors. Diagnosis can be challenging and requires genomic testing for confirmation.Case Report:A 40-year-old woman presented with a breast mass found on mammography. She underwent an ultrasound-guided biopsy of the tumor. Initial pathology evaluation revealed features consistent with invasive ductal carcinoma. The immunochemistry report described an ER-positive, PR-negative, and HER2-negative tumor. The specimen was sent for oncotype scoring, which was not performed due to the specimen not meeting the criteria for invasive ductal carcinoma and displaying pathological features of SBC. A fluorescent in situ hybridization (FISH) study revealed ETV6 translocation, consistent with the diagnosis of SBC. The patient underwent lumpectomy followed by adjuvant radiotherapy and endocrine therapy. She remains in complete remission 3 years after treatment.Conclusions:Accurately diagnosing SBC is of extreme importance as it has an indolent clinical course, but has a favorable prognosis if detected early. Due to nonspecific imaging findings, pathology evaluation with immunohistochemical staining followed by genomic testing is required. Our case highlights the challenges associated with SBC diagnosis requiring genomic testing due to equivocal pathological findings, along with increasing incidence of SBT in adults. There are no established guidelines for SBC management. The mainstay of treatment is partial or total mastectomy. Data on the benefits of adjuvant endocrine therapy, chemotherapy, and radiotherapy are inconclusive.

Therapeutic targeting of RBPJ, an upstream regulator of ETV6 gene, abrogates ETV6-NTRK3 fusion gene transformations in glioblastoma

Fusion genes are abnormal genes resulting from chromosomal translocation, insertion, deletion, inversion, etc. ETV6, a rather promiscuous partner forms fusions with several other genes, most commonly, the NTRK3 gene. This fusion leads to the formation of a constitutively activated tyrosine kinase which activates the Ras-Raf-MEK and PI3K/AKT/MAPK pathways, leading the cells through cycles of uncontrolled division and ultimately resulting in cancer. Targeted therapies against this ETV6-NTRK3 fusion protein are much needed. Therefore, to find a targeted approach, a transcription factor RBPJ regulating the ETV6 gene was established and since the ETV6-NTRK3 fusion gene is downstream of the ETV6 promoter/enhancer, this fusion protein is also regulated. The regulation of the ETV6 gene via RBPJ was validated by ChIP analysis in human glioblastoma (GBM) cell lines and patient tissue samples. This study was further followed by the identification of an inhibitor, Furamidine, against transcription factor RBPJ. It was found to be binding with the DNA binding domain of RBPJ with antitumorigenic properties and minimal organ toxicity. Hence, a new target RBPJ, regulating the production of ETV6 and ETV6-NTRK3 fusion protein was found along with a potent RBPJ inhibitor Furamidine.

Abstract CT545: Variability in NTRK gene fusions does not appear to impact response to larotrectinib

Abstract Introduction: Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are oncogenic drivers in various tumor types. Gene fusions arise from inter- and intrachromosomal rearrangements involving the 3’ region of the NTRK gene and the 5’ end of a fusion partner gene, leading to the expression of a constitutively active tropomyosin receptor kinase (TRK) fusion protein. Larotrectinib is a highly selective and central nervous system (CNS)-active TRK inhibitor approved for the treatment of adult and pediatric patients with TRK fusion cancer. Larotrectinib has previously demonstrated an objective response rate (ORR) of 75% in 206 patients with non-primary CNS solid tumors (Hong et al, ASCO 2021). Here, we report on the TRK fusion exon junction organization in patients with TRK fusion cancer receiving larotrectinib. Methods: Patients with non-primary CNS TRK fusion cancer treated with larotrectinib were identified from three clinical trials (NCT02122913, NCT02576431, and NCT02637687). NTRK gene fusion data were determined by local molecular testing. The testing method, NTRK gene fusions, and exon structure were extracted from the molecular pathology reports from 212 patients. The data cut-off was July 20, 2020. Results: TRK fusion exon junction data were available for 80 patients from 14 different tumor types. Median age was 47 years (range 0.5-84 years). The ORR for these patients was 82.5% (95% confidence interval [CI] 72.4-90.1). Patients had gene fusions involving NTRK1 (40%), NTRK2 (4%), or NTRK3 (56%), a pattern similar to that seen in the larger dataset. We detected 20 different NTRK gene fusions; the most common were ETV6-NTRK3, TPM3-NTRK1, and LMNA-NTRK1 detected in 39 (49%), ten (13%), and seven (9%) patients, respectively. There were 12, three, and five different fusion partners associated with NTRK1, NTRK2, and NTRK3, respectively. The majority (12/20; 60%) of fusions were intrachromosomal rearrangement events: 8/12 (67%) related to NTRK1, 2/3 (67%) related to NTRK2, and 2/5 (40%) related to NTRK3. There were 35 different 5’/3’ gene breakpoint combinations: 3’ fusion points were located at NTRK1 exon 8 (n = 2), NTRK1 exon 9 (n = 5), NTRK1 exon 10 (n = 15), NTRK1 exon 11 (n = 6), NTRK1 exon 12 (n = 3), NTRK1 exon 13 (n = 1), NTRK2 exon 15 (n = 2), NTRK2 exon 16 (n = 1), NTRK3 exon 14 (n = 21), and NTRK3 exon 15 (n = 24). For ETV6-NTRK3 fusions, the NTRK3 fusion point was at exon 14 in ten of 11 thyroid carcinomas, but in only three of 13 salivary gland tumors. Conclusions: Among 80 patients with TRK fusion cancer, we detected 20 different NTRK gene fusions, of which 55% occurred in only one patient each. There were 36 different fusion variants. Despite the variability of the fusion structure, larotrectinib was equally efficacious. The large number of potential different fusion partners and involvement of various breakpoints highlight the need for validated and appropriate testing methodologies that are agnostic of 5’ partners and breakpoints. Citation Format: Marc Ladanyi, Sinchita Roy-Chowdhuri, Lauren Ritterhouse, Felix Sahm, Ricarda Norenberg, Kui Shen, Chi Chen, Marc Fellous, Nicoletta Brega, Cornelis M. van Tilburg, Jessica J. Lin, Marcia S. Brose, Ulrik N. Lassen, Ray McDermott, Theodore W. Laetsch, David S. Hong, Alexander Drilon, Erin R. Rudzinski. Variability in NTRK gene fusions does not appear to impact response to larotrectinib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT545.

A rapid and durable response to larotrectinib in a patient with NTRK fusion-positive secretory carcinoma originating from the external auditory canal

For decades, no clear consensus existed on the standard treatment option for malignant tumors of the external auditory canal, an extremely rare disease. Here we report the case of a 55-year-old female patient with secretory carcinoma that originated from the left external auditory canal. Magnetic resonance imaging (MRI) at baseline showed that the tumor had extended to the medulla oblongata despite surgical and radiation treatments for more than 20 years from the initial diagnosis. Based on the results of a next-generation sequencing test of a formalin-fixed paraffin-embedded surgical specimen indicating that the tumor harbored ETV6–NTRK3 fusion, the patient was enrolled in a global basket study of larotrectinib, an oral selective tropomyosin receptor kinase (TRK) inhibitor. Three weeks after the start of larotrectinib treatment, MRI showed only small remnants of the tumor in the medulla oblongata and the patient’s headache before the treatment had disappeared. Subsequent MRI after 12 weeks of treatment confirmed the complete disappearance of the tumor. The patient repeated grade 2 flu-like symptoms related to treatment, but did not experience any other grade 2 or worse treatment-related adverse events. TRK inhibitors, such as larotrectinib, exert potent antitumor activity against neurotrophic tyrosine receptor kinase (NTRK) fusion-positive tumors in a tumor-agnostic manner. To the best of our knowledge, this is the first report on NTRK fusion-positive secretory carcinoma of the external auditory canal, and this report provides a valuable insight into the management of the extremely rare but now treatable malignancy.

Secretory Carcinoma of the Salivary Glands


 
 
 
 A 29-year-old woman presented with a 3-month history of an enlarging right infra-auricular mass. A fine needle aspiration biopsy revealed a cellular aspirate consistent with a salivary gland neoplasm of uncertain malignant potential (The Milan System for Reporting Salivary Gland Cytopathology Category IV-B). She subsequently underwent superficial parotidectomy, revealing a poorly circumscribed tumor measuring 1.8 x 1.2 x 1.0 cm in the superficial lobe of the parotid gland.
 
 
 
 
 On microscopic examination, the tumor was composed of microcystic, follicular, and tubular structures lined by mildly atypical, hobnailed cells with abundant granular to foamy, pale, eosinophilic cytoplasm, and round to oval, vesicular nuclei containing finely granular chromatin and prominent, centrally located nucleoli. (Figure 1) Intraluminal secretions were present within the microcysts and tubules, staining positive for Periodic Acid Schiff (PAS) that was resistant to diastase digestion. (Figure 2) Immunohistochemistry studies for S100, SOX10, and Mammaglobin showed strong, diffuse positivity in the tumor cells, in contrast to the absence of staining observed for DOG1. (Figure 3) Given the described morphological and immunological findings, a diagnosis of secretory carcinoma was rendered. No foci of high-grade transformation, i.e., areas with a solid growth pattern, nuclear anaplasia, increased mitoses, or necrosis, were noted.
 
 
 
 
 Secretory Carcinoma or Mammary Analogue Secretory Carcinoma (MASC) is a recently described low grade salivary gland malignancy that bears a morphologic resemblance to mammary secretory carcinoma, harboring a similar chromosomal translocation, t(12;15) (p13;q25), that most commonly produces a fusion of the ETV6 and NTRK3 genes.1-5 Occurring in adults (mean patient age of 46.5 years) without a predilection for either sex, these tumors most commonly arise in the parotid gland.1,2
 
 
 
 
 Historically, secretory carcinomas have been diagnosed as either acinic cell carcinoma – due to the close morphological similarity of having a microcystic or follicular growth pattern or adenocarcinoma that is not otherwise specified. Aside from the characteristic ETV6-NTRK3 gene fusion, secretory carcinomas may be differentiated from acinic cell carcinoma by having no basophilic zymogen cytoplasmic granules in the tumor cells in contrast to the latter, and the diffuse expression of S100 and Mammaglobin as well as the absence of DOG1 expression in secretory carcinoma on immunohistochemistry. 1,2 Low grade mucoepidermoid carcinoma may also present as a possible morphological differential diagnosis. Immunohistochemistry studies for p63 (expressed in epidermoid cells of mucoepidermoid carcinoma), as well as S100 and Mammaglobin (no expression expected in mucoepidermoid carcinoma) may be sufficient to differentiate between the two entities. On a cytogenetic level, most low grade mucoepidermoid carcinomas harbor a chromosomal translocation, t(11:19), that results in a characteristic CRTC1-MAML2 gene fusion in contrast to the ETV6-NTRK3 fusion seen in secretory carcinoma.1-3 The light microscopic features of this particular case however are sufficiently distinct from a mucoepidermoid carcinoma that we felt that this entity could be excluded based on routine H&E morphology. It is granted however, that molecular testing, e.g., in-situ hybridization to demonstrate characteristic chromosomal aberrations, may prove valuable in morphologically ambiguous cases. Its unavailability in the local setting is thus a limitation.
 
 
 
 
 
 
 
 
 Secretory carcinomas are mostly reported to be indolent though are associated with lymph node metastasis in up to 25% of cases. Like other low grade salivary gland carcinomas, locoregional recurrence and distant metastasis have been documented in rare cases. However, high clinical grade and high-grade morphological transformation have been reported and are associated with adverse outcomes.1,2,4,5 The patient tolerated the surgical procedure well, and had no evidence of disease eight months after the operation. Reporting this fairly uncommon entity is encouraged to further expand our understanding of its biology and natural history.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

HGG-37. A case ofETV6-NTRK3 fusion driven infantile hemispheric glioma (IHG) with acquired drug resistance against first- and second-generation NTRK-inhibitors

A 3-month-old girl had left cerebral infantile hemispheric glioma (IHG), H3 wild type (wt), Grade IV (WHO2020) with diffuse leptomeningeal and spinal metastasis. Craniotomies were performed twice which achieved partial resection. Histopathology revealed high grade glioma, Ki67 30-40%, mitosis and widespread necrosis. IHC showed H3wt, IDH-, and retained INI-1. RNAseq found ETV6-NTRK3 fusion. She was treated per Baby POG-9233, however after 3 cycles, there was mixed response (static for primary, partial response for metastasis). She had severe developmental delay, right hemiparesis and dysphagia. Aiming for better disease control and potential resectability, we switched to first-generation NTRK-inhibitor, Larotrectinib. MRI at 3 months showed significant interval reduction in tumour size, then became static at 6 months. She was stable with gradual neurological improvement until 10 months after Larotrectinib, there was worsening neurology and imaging confirmed tumour progression with haemorrhage. Craniotomy was performed for haemostasis and tumour debulking. Histopathology showed same IHG with ETV6-NTRK3 fusion. Targeted panel sequencing found NTRK3 p.Gly623Arg mutation, a solvent-front substitution responsible for acquired resistance to first-generation TRK-inhibitors. BRAFV600E and MET amplification were not detected. Larotrectinib was switched to second-generation NTRK-inhibitor, Selitrectinib. MRI at 1 month showed post-operative changes, but disease progressed at 3 months and in an accelerated manner over the course of 10 days while on therapy. Choice of conventional chemotherapy and radiotherapy were discussed, but the girl deteriorated rapidly and deceased (3 months from start of Selitrectinib, 19 months from diagnosis). CONCLUSION: IHG is aggressive with challenging surgery and medical treatment. The use of small molecular inhibitor requires careful consideration, i.e. treatment effect, toxicity and potential acquired drug resistance as showed in this case. For unresectable tumour, it may be inevitable as we also reported a similar case with ROS1 fusion. Access to newer novel agents is difficult while therapeutic effect is uncertain.

Mammary analog secretory carcinoma in adults: A systematic review.

e18076 Background: Mammary analog secretory carcinoma (MASC) is a rare malignant salivary gland tumor of the head and neck region that was first described by Skálová et al. in 2010. It histologically mimics breast secretory carcinoma and parotid acinic cell carcinoma, and characterized by ETV6-NTRK3 fusion gene. This review aims to investigate the clinicopathologic features, treatment, and outcomes of MASC in adults. Methods: PubMed search for MASC adults (18+ years) from data inception through 2021, pooled with a case from our institution. Kaplan-Meier analysis was used to plot survival curves. Results: Of the 254 included cases, female:male ratio 1.02:1 with a mean age at diagnosis (±SD, range) of 50.1 (±16.7, 18–86) years. In terms of location, 143 (56.3%) occurred in the parotid gland, 21 (8.3%) in the submandibular gland, 21 (8.3%) in the lip, 15 (5.9%) in the thyroid gland–all (100%) had a component of classical type papillary carcinoma, 15 (5.9%) were cutaneous, 13 (5.1%) in the buccal mucosa, 12 (4.7%) split between hard and soft palate, 4 (1.6%) in the nasal mucosa, 2 (0.8%) in the lung, and remaining 8 (3.1%) each in the conjunctiva, tongue, minor salivary gland, submaxillary gland, maxillary sinus, ethmoid sinus, upper esophagus, and mandible. Patients mostly presented with swelling or growing mass in 95.4% (out of which, 93.3% were painless), followed by a painful ulcer in 1.8%. Median tumor size was 1.9 cm (range 0.3cm–8.5cm). Median duration of symptoms at time of presentation was 12 (range 1-360) months. Tumors were T1 (49.7%), T2 (23.9%), T3 (20.3%), and T4 (6.1%), N0 (81.9%), N1 (10.7%), N2 (7.4%), M0 (97.4%), and M1 (2.6%). Most patients (70.7%) presented as early stage (I or II) which was associated with a high survival probability based on a log-rank test (p-value: 0.0007). All patients had surgical resection, mostly combined with neck dissection (ND) in11.4%, radiation (RT) in 7.8%, ND+RT in 4.7%, ND with platinum-based chemoradiation in 1.0%, and one case reported use of Crizotinib followed by Entrectinib with disease progression at 4.5 and 7 months, respectively. Among patients with reported outcomes, 92.2% were alive with a median follow-up of 26 (range 1-228) months, and 7.8% deceased with a median time-to-death of 29 (range 1-107) months. Eleven (4.3%) reported a high-grade MASC and 18.5% of patients lived for over five years after their diagnosis. Conclusions: Early stage was a notable predictor of higher survival probability in MASC patients. Its rarity, heterogeneity of clinical behaviors, and variable outcomes make it even more challenging. This review serves as real-world evidence to further our understanding of this rare entity and shed light on prospective clinical trial design.

Larotrectinib Treatment for Patients With TRK Fusion-Positive Salivary Gland Cancers.

Larotrectinib is a first-in-class, highly selective, and central nervous system-active tropomyosin receptor kinase (TRK) inhibitor approved for the treatment of adult and pediatric patients with TRK fusion cancer. We report the efficacy and safety of larotrectinib in patients with TRK fusion-positive salivary gland cancers. Patients with TRK fusion-positive salivary gland cancer treated with larotrectinib were identified from two clinical trials (NCT02122913 and NCT02576431). Patients received larotrectinib 100 mg twice daily (BID) except for one patient who received 150 mg BID in the phase I trial. The primary endpoint was objective response rate (ORR) as assessed by the investigator using Response Evaluation Criteria in Solid Tumors version 1.1. At the data cut-off (July 20, 2020), 24 patients with TRK fusion-positive salivary gland cancer had been treated. The most common histologies were secretory carcinoma (54%), adenocarcinoma (25%), and mucoepidermoid carcinoma (13%). All 24 patients had an ETV6-NTRK3 gene fusion. The ORR was 92% (95% confidence interval, 73-99). Best overall response was complete response in three (13%) patients, partial response in 19 (79%), and progressive disease in two (8%). The rate of progression-free survival at 24 months was 78% (median follow-up 30.9 months). Most treatment-related adverse events (AEs) were grade 1-2, and no patients discontinued treatment due to AEs. Larotrectinib demonstrated robust and durable efficacy in patients with TRK fusion-positive salivary gland tumors of various histologies, and a favorable safety profile. These findings support NTRK gene fusion testing in patients with advanced salivary gland cancers. NCT02122913 and NCT02576431.

Secretory carcinoma of the salivary gland, a rare entity: An international multi‐institutional study

BACKGROUNDSecretory carcinoma (SC) of the salivary gland is a rare entity with limited published literature on cytomorphology. The authors present the largest cohort to date of SC fine‐needle aspiration (FNA) cases.METHODSFNA cases of histologically confirmed SC were retrospectively retrieved from 12 academic institutions in the United States, Italy, Finland, and Brazil. The collated data included patient demographics, imaging findings, cytopathologic diagnoses according to the Milan System for Reporting Salivary Gland Cytopathology, cytomorphologic characteristics, and immunohistochemical/molecular profiles.RESULTSIn total, 40 SCs were identified (male‐to‐female ratio, 14:26) in patients with a mean age of 52 years (age range, 13‐80 years). Ultrasound imagining revealed a hypoechoic, ovoid, poorly defined, or lobulated mass. The most common primary site was the parotid gland (30 of 40 tumors). Regional lymph node metastasis (9 patients) and distant metastasis (4 patients; brain, liver, lungs, and mediastinum) were noted. Two patients died of disease. FNA smears were cellular and demonstrated mainly large, round cells with intracytoplasmic vacuoles or granules and round‐to‐oval nuclei with smooth nuclear contour, minimal irregularities, and prominent nucleoli arranged predominantly in clusters, papillary formations, and single cells. The background was variable and contained inflammatory cells, mucin, or proteinaceous material. The diagnoses were malignant (19 of 38 tumors; 50%), suspicious for malignancy (10 of 38 tumors; 26%), salivary gland neoplasm of uncertain malignant potential (7 of 38 tumors; 18%), and atypia of undetermined significance (2 of 38 tumors; 6%) according to the Milan System for Reporting Salivary Gland Cytopathology. Two malignant cases (2 of 40 tumors; 5%) were metastases. The neoplastic cells were immunoreactive for S100 (23 of 24 tumors), mammaglobin (18 of 18 tumors), GATA‐3 (13 of 13 tumors), AE1/AE3 (7 of 7 tumors), and vimentin (6 of 6 tumors). ETV6‐NTRK3 fusion was detected in 32 of 33 tumors by fluorescence in situ hybridization (n = 32) and next‐generation sequencing (n = 1).CONCLUSIONSFamiliarity with cytomorphologic features and the immunohistochemical/molecular profile of SC can enhance diagnostic accuracy.;

Сongenital infantile fibrosarcoma with a non-canonical TPM3-NTRK1 fusion transcript: a case report and a literature review

Infantile fibrosarcoma (IFS) is a rare malignant soft tissue tumor characterized by local invasion, a low rate of distant metastasis (1–13%), and manifestation during the first years of life. Overall survival rates range from 89 to 94%, event-free survival rates – from 81 to 84%. Classic IFS is characterized by t(12;15)(p13;q25) translocation resulting in the formation of the ETV6-NTRK3 fusion transcript. However, over the past few years, there have been numerous reports of IFS-like tumors with non-canonical genetic aberrations (BRAF, NTRK1, MET genes) whose prognosis is less predictable. Here we report a rare case of congenital IFS with involvement of subcutaneous fat, indolent course and a non-canonical TPM3-NTRK1 fusion transcript identified in the soft tissue and intradermal tumor components with different histological features. The patient’s parents gave their consent to the use of their child’s data, including photographs, for research purposes and in publications. The literature review explores modern algorithms for the diagnosis and treatment of IFS in children, including the use of new therapies, such as tropomyosin receptor kinase inhibitors, as well as algorithms for detecting NTRK1, NTRK2, NTRK3 gene rearrangements in solid neoplasms in general, and soft tissue tumors in particular.

NTRK Fusions Detection in Paediatric Sarcomas to Expand the Morphological Spectrum and Clinical Relevance of Selected Entities.

Undifferentiated round cell sarcomas (URCS) of soft tissue and bone and tumours of uncertain differentiation (TUD) are commonly ascribed to a subset of neoplasms with low frequency of NTRK gene fusions. However, more recently NTRK-rearranged round and spindle cell tumours have been noted in case reports and in limited or heterogeneous cohorts. The aim of our study was to investigate the presence of NTRK gene fusions in a large retrospective cohort of paediatric URCS and TUD after a systematic review of the diagnosis, according to the recently updated WHO classification scheme. One-hundred and five patients with diagnosis of URCS or TUD, involving the bone or soft tissue, were retrospectively evaluated. After the case selection and the histopathological review of the case cohort, pan-Trk immunohistochemistry (IHC) testing was performed on formalin-fixed paraffin-embedded (FFPE) tissues. Tumour RNA was extracted from FFPE tissue and subjected to next-generation sequencing (NGS) library preparation, using a 10-gene NGS fusion panel, sequenced on an Illumina MiSeq. The NGS-positive cases were further confirmed by real-time PCR. On immunohistochemical screening, 12/105 (11.4%) cases were positive using the pan-Trk antibody, showing three different staining patterns with the cytoplasmic distribution being most common. Molecular analysis using NGS and confirmed by the real-rime PCR detected two positive cases for the ETV6-NTRK3 fusion. The histological pattern of the two positive cases, together with the demonstration of the NTRK rearrangement, leaded to re-classify these previously not otherwise specified sarcomas with uncertain differentiation into the emerging category of NTRK-rearranged neoplasms. In addition, we found the two NTRK fused neoplasms showing a clinical indolent course, in contrast with literature.