Cytologic Atypia Research Articles

Signet-ring cell sinus histiocytosis: report of the clinicopathologic characteristics of 4 cases with emphasis on the differential diagnosis of signet-ring cell lesions

Signet-ring cell sinus histiocytosis (SRCSH) represents a distinctly rare reactive phenomenon predominantly affecting axillary and pelvic lymph nodes (LNs) of individuals with breast or prostatic adenocarcinoma. Reports of SRCSH in the literature are sparse with only 12 previous examples, thus underscoring the rarity of this process. Here, we report 4 additional SRCSH cases affecting 2 women and 2 men (M:F = 1:1; age range: 50 to 71 years; mean age = 61 years). In the 2 men, pelvic LNs were excised during radical cystoprostatectomy for genito-urinary cancer, while in one woman SRCSH was incidentally discovered in axillary LNs during mastectomy for breast adenocarcinoma. The other female patient presented with a history of aortic valve replacement and enlarged supraclavicular LNs. Microscopically, all involved LNs exhibited marked distention with filling of the subcapsular and medullary sinuses by sheets of signet-ring histiocytes containing a singular large, cytoplasmic vacuole and a crescentric nucleus. Overt cytologic atypia, pleomorphism and mitoses were absent. Erythrophagocytosis and occasional fibrosis were appreciated. None of the LNs with SRCSH showed evidence of metastatic tumor. Immunohistochemically, signet-ring sinus histiocytes were invariably positive for CD68 and CD163 but negative for pancytokeratins. The histopathologic characteristics of SRCSH, albeit bland, in conjunction with the patient's medical history, may be misinterpreted as metastatic adenocarcinoma with signet-ring cell configuration. Immunohistochemical confirmation of the histiocytic lineage of the lesional cells in SRCSH usually suffices for rendering an accurate diagnosis. The underlying pathogenetic mechanism and possible biologic significance of SRCSH remain currently unknown.

Shift and longtime light induces endometrioid adenocarcinoma via activation of PKC-α/Akt pathway in female golden hamster: Involvement of altered Aanat and Bmal1 rhythm.

Female night-workers get exposed to frequent light shifts, hence have altered circadian rhythm and are at high risk of endometrial cancer; the underlying mechanism however is still not clear. We, therefore examined the effect of long light exposure (16L:8D, LD1) and regular shift (8 h) in long nighttime (LD2) on endometrial changes of female golden hamsters. Morphometric analysis, scanning electron microscopy imaging, alcian blue staining, and cytological nuclear atypia of endometrial stromal cells confirmed the incidence of endometrial adenocarcinoma in LD2 exposed hamsters. But, less severe pathomorphological alterations were noted in uterus of LD1 exposed hamsters. Altered Aanat and Bmal1 mRNA, melatonin rhythm, downregulation of important marker gene of adenocarcinoma like Akt, 14-3-3, and PR protein expression and upregulation PKCα, pAkt-S473 and vascular epithelial growth factor (VEGF) were observed in LD2 exposed hamsters suggesting the endometrial adenocarcinoma. Further, our western blot analysis supported the immunohistochemical localization of PR, PKCα, and VEGF in uterine tissues along low progesterone. Overall, our data indicates that light shift and long light exposure potentially induced endometrioid adenocarcinoma via activation of PKC-α/Akt pathway in female hamsters. Therefore, duration of light is essential for female normal uterine function.

Probability of malignancy and molecular alterations as determined by ThyroSeq v3 genomic classifier in Bethesda Category IV.

ThyroSeq molecular testing assesses the probability of malignancy (POM) in thyroid fine-needle aspiration cytology (FNAC) with indeterminate cytology. The aim was to investigatewhether Bethesda category IV (BIV) subcategories are associated with specific molecular alterations, molecular-derived risk of malignancy (MDROM), and risk of malignancy (ROM). FNAC slides, associated ThyroSeq, version 3, Genomic Classifier results, and surgical follow-up were retrieved for BIV nodules. Nodules were subcategorized as follicular neoplasm (FN) with or without cytologic atypia or oncocytic follicular neoplasm (OFN). The MDROM, ROM, and frequency of molecular alterations in FN and OFN were analyzed. p < .05 was considered significant. A total of 92 FNAC were identified and subcategorized into 46 FN (15 with and 31 without cytologic atypia) and 46 OFN. The benign call rate and the positive call rate were 49% and 51%, respectively. The MDROM in BIV was 34.3%, trending lower in OFN than in FN. RAS mutations were significantly more frequent in FN when compared to OFN (p = .02). Chromosomal copy number alterationswere more often present in OFN than in FN (p < .01). On histologic follow-up, ROM in OFN was trending lower than in FN (p = .1). The most common diagnosis in OFN was oncocytic adenoma, whereas follicular variant papillary thyroid carcinoma was most common in FN. The MDROM and ROM were trending lower in OFN compared with FN, and the molecular alterations differed between OFN and FN subcategories.

DP18 Extraocular sebaceous carcinoma in situ

Abstract Extraocular sebaceous carcinoma in situ (SCIS) is exceedingly rare with &amp;lt; 10 cases reported in the literature (Jeong KM, Seo JY, Kim A et al. Extraocular sebaceous carcinoma in situ concurrent with actinic keratosis: a case report and review of the literature. Korean J Dermatol 2021; 59:307–9). An 80-year-old man reported a 3-month history of a right forehead lesion that had been bleeding. This was a subtle 5 × 5 mm papule on clinical examination, and dermoscopy showed arborizing telangiectasia. Past medical history was significant for 20 basal cell carcinomas, one squamous cell carcinoma, Bowen disease and actinic keratoses. Histology showed sun-damaged skin with a partially eroded neoplasm of lobular architecture, with surface and infundibular epithelium containing atypical sebocytes and squamous cells with no infiltrative growth pattern, which was consistent with SCIS and was fully excised. Immunohistochemistry revealed patchy adipophilin and androgen receptor staining and stronger epithelial membrane antigen staining. Furthermore, there was preserved expression of MSH2, MSH6, MLH1 and PMS2. Sebaceous carcinoma in situ is a debated entity not formally recognized in the classification of sebaceous neoplasms. Kazakov et al. reported five cases of dermal sebaceous tumours with ‘benign’ architectural features (well-circumscribed and no evidence of invasion) but with cytological atypia (abnormal mitoses and pleomorphism) (Kazakov D, Kutzner H, Spagnolo DV et al. What is extraocular cutaneous sebaceous carcinoma in situ? Am J Dermatopathol 2010; 32:857–8). The authors questioned whether these cases represented sebaceous adenomas with atypia or sebaceous carcinomas (Kazakov et al.). In response, it has been argued that such architectural–cytological discordant tumours can be regarded as SCIS owing to the fact that, by definition, carcinoma in situ is a cancer that remains wholly at the site of origin. However, it is argued that these lesions have an unclear origin and may not arise from sebaceous glands in the skin, unlike the more common aggressive periorbital sebaceous carcinomas that arise from meibomian glands and glands of Zeis (Kazakov et al.). It has been postulated that a SCIS diagnosis should be reserved for intraepidermal tumours not extending beyond the epidermal basement membrane, which is a vanishing minority of sebaceous neoplasms (Kazakov et al.). Similar to our case, a 2021 case report identified SCIS without any connection to an adnexal component but concurrent with actinic keratosis. These authors proposed that the tumour cells of intraepidermal squamous neoplasia can differentiate towards malignant sebocytes (Jeong et al.). Although controversial, SCIS appears to have reasonable, clear histological criteria for diagnosis and an excellent prognosis, with no reports of recurrence following surgical excision. We feel it is important to increase identification to avoid the overtreatment of such lesions.

DP25 Widespread subcutaneous nodular kappa light chain amyloidosis

Abstract A 69-year-old woman was referred to the dermatology department for evaluation of multiple widespread subcutaneous lesions involving the neck, torso and limbs. These lesions, initially diagnosed in the community as lipomas, had been slowly progressing in size and number for 3 years. She had remained systemically well. Her only medical history was essential thrombocythaemia. She took no regular medication. On examination, there were multiple subcutaneous lesions appreciated on palpation with no overlying epidermal change. The patient was experiencing pain in a sciatic distribution. Magnetic resonance imaging of the femur showed a 12-cm enhancing area of subcutaneous nodularity encasing the sciatic nerve. Computed tomography of the chest, abdomen and pelvis showed multiple subcutaneous, ill-defined, soft tissue lesions of the anterior abdominal wall with no lymphadenopathy or organ abnormality. Deep incisional biopsies from two separate locations were completed. There was an unremarkable epidermis and dermis. In the subcutaneous fat, the septae appeared thickened alongside thickened elastic fibres and a prominent multifocal granulomatous reaction with a high degree of elastophagocytosis. There were multifocal aggregates of plasma cells that displayed no cytological atypia. In situ hybridization showed strong kappa light chain restriction. Plasma protein electrophoresis was completed and confirmed a paraprotein band in the gamma region of IgM kappa. Full blood count revealed a high platelet count (585 × 109 cells L–1) but was otherwise unremarkable alongside normal renal and liver function, bone profile, lactate dehydrogenase, B2 microglobulin, Bence–Jones proteins and infection screen. A Congo red stain was performed on the original histological samples. This showed apple green birefringence under polarized light-confirming amyloid. Haematology completed a bone marrow biopsy, which was normal. Referral to the National Amyloid Centre was made. Serum amyloid P scan showed no visceral involvement. A diagnosis of subcutaneous amyloid kappa light chain subtype (AL) was made. The patient has since commenced rituximab, bortezomib (Velcade®), cyclophosphamide and dexamethasone (R-VCD) chemotherapy at 4-weekly intervals over a 4-month period. Primary localized cutaneous amyloidosis is characterized by extracellular deposition of amyloid protein in the skin without evidence of systemic involvement and is often subtyped into macular, papular and nodular. Amyloidoma (tumoral amyloidosis) is rare and defined as a solitary localized deposit of amyloid. There are only four case reports in the literature of multiple subcutaneous amyloid deposits, and only one of these cases was of AL (light chain) vs. amyloid A (AA) subtype. This case showed nodules restricted to the neck (Nguyen TU, Oghalai JS, McGregor DK et al. Subcutaneous nodular amyloidosis: a case report and review of the literature. Hum Pathol 2001; 32:346–8). To our knowledge, this is the first case of widespread kappa light chain subcutaneous amyloidosis.

Hepatic Angiosarcomas With Sinusoidal Growth Patterns.

Hepatic angiosarcomas are aggressive malignant tumors of the liver with variable morphology. One of the rare morphologies is that of the sinusoidal growth pattern, which is challenging to diagnose because of its subtle imaging and morphologic findings. This retrospective study characterizes the clinical, histologic, and immunohistochemical features of sinusoidal hepatic angiosarcomas. Thirteen cases were included in the study, comprising 12 (92.3%) needle core biopsies and 1 wedge biopsy; one of the needle biopsies also had a subsequent resection specimen available for review. Multiple biopsies were needed to make the diagnosis in 4 cases. At least moderate sinusoidal dilatation was seen in 53.8% of cases. Increased cellularity within the sinusoids was seen at both low-power and high-power magnification (69.2% and 84.6%, respectively). Cytologic atypia ranged from mild to marked. Multinucleated tumor cells were present in most cases (10/13 cases) but were often sparse. Mitotic activity was identified in 5/13 cases. ERG immunostains were more reliable than CD31 and CD34 in identifying the tumor cells. Ki-67 proliferative index ranged from 5% to 30%. p53 immunostains were available in 9 cases and c-MYC in 7 cases; they were positive in 62.5% and 33.3% of cases, respectively and had a mutually exclusive staining pattern. In summary, this rare pattern of hepatic angiosarcoma is challenging to diagnose but has distinctive morphologic findings that can be supplemented with immunostains to establish the diagnosis.

Primary epithelioid hemangioendotheliomas and angiosarcomas of the pleura: a clinicopathological and immunohistochemical analysis of 13 cases

Thirteen cases of primary epithelioid hemangioendotheliomas (EHE) and epithelioid angiosarcomas (EA) of the pleura are presented. The patients were 7 men and 6 women between the ages of 34 and 65 years (mean: 47 years). The patients presented with non-specific symptoms of cough, dyspnea, and chest pain. Diagnostic imaging revealed the presence of either diffuse pleural thickening or pleural nodules involving the serosal surfaces. Open surgical biopsies were obtained in all cases. Histologically, eight tumors were characterized by the presence of a cellular proliferation composed of medium-sized epithelioid cells embedded in a myxohyaline stroma and a variable spindle cell component. Cellular atypia was mild to moderate and mitotic activity ranged from 1 to 2 per 2mm2. Immunohistochemical stains for vascular markers, including CAMTA1 were positive, confirming a diagnosis of EHE. Five cases of epithelioid angiosarcomas were characterized by a neoplastic cellular proliferation admixed with areas of necrosis and hemorrhage and characterized by medium-sized epithelioid to spindle-shaped cells with eosinophilic cytoplasm, round to oval nuclei and prominent nucleoli. In addition, marked cytologic atypia and a mitotic activity ranging from 3 to 5 per 2mm2 were identified. Immunohistochemical studies demonstrated positive staining for vascular markers; however, CAMTA1 was negative. Clinical follow-up obtained in eleven cases showed that all patients had died within 30 months post diagnosis. The current study highlights that even though it may be important to histologically separate EHE from EA for academic purposes, primary pleural origin of these tumors appears to portent an aggressive clinical behavior.

"PRRX1-rearranged mesenchymal tumors": expanding the immunohistochemical profile and molecular spectrum of a recently described entity with the proposed revision of nomenclature.

Since the publication of the 2020 World Health Organization classification of soft tissue and bone tumors, the classification of "fibroblastic" tumors has expanded to include a novel subset of tumors characterized by PRRX1::NCOA1/2 gene fusions. These tumors defy conventional classification and are morphologically distinct, characterized by a multi-nodular growth of bland spindle cells suspended in a myxo-collagenous stroma with mild cytologic atypia, "staghorn-like" vessels, and variable perivascular hyalinization. Mitotic activity is rare, and necrosis is not identified. Herein, we present six additional cases of PRRX1-rearranged mesenchymal tumors, including five cases with PRRX1::NCOA1 fusion and one case with PRRX1::KMT2D fusion. Three cases (3/6, 50%) demonstrated focal co-expression of S100 protein and SOX10, thereby expanding the immunohistochemical profile of this emerging entity. Like prior reported cases, there was no evidence of malignant behavior on short-term follow-up. The novel fusion, PRRX1::KMT2D, further expands the molecular spectrum of this entity and leads to a proposed revision of the provisional nomenclature to "PRRX1-rearranged mesenchymal tumor" to both accommodate non-NCOA1/2 fusion partners and allow for the possibility of partial neural or neuroectodermal differentiation.

Claudin-4 Expression in the Distinction of Mammary and Extramammary Paget Disease From Morphologic Mimics: Diagnostic Utility and Pitfalls.

Claudin-4 Expression in the Distinction of Mammary and Extramammary Paget Disease From Morphologic Mimics: Diagnostic Utility and Pitfalls.

Rectovaginal endometriosis with nodular smooth muscle metaplasia diagnosed via transrectal ultrasound-guided fine-needle aspiration cytology: An underused minimally invasive diagnostic technique?

Rectovaginal endometriosis is a severe variant of deeply infiltrating endometriosis. Laparoscopic assessment with tissue sampling remains the gold standard for diagnosis of endometriosis. However, transvaginal (TVUS) and transrectal ultrasound (TRUS) have been shown to be especially helpful in the diagnosis of deep endometriosis. We present the case of a 49-year-old female with menorrhagia, dysmenorrhea, and constipation. Upon pelvic examination, an incidental mass was palpated. A computed tomography (CT) scan revealed an anterior rectal wall mass and colonoscopy was non-diagnostic. Further work-up with MRI showed a 3.9 cm mass centered within the upper rectovaginal septum. TRUS guided fine-needle aspiration (TRUS-FNA) revealed cohesive epithelial cell groups without significant cytologic atypia and a second population of bland spindle cells. Cell block slides showed glandular epithelium with associated stroma that exhibited endometrial morphology and immunophenotype. Nodular fragments of spindle cells with smooth muscle immunophenotype and fibrosis were also present. The overall morphologic findings were consistent with rectovaginal endometriosis with nodular smooth muscle metaplasia. Medical management with nonsteroidal aromatase inhibitor with radiologic follow-up was selected. Rectovaginal endometriosis represents a type of deep endometriosis usually associated with severe pelvic symptoms. Metaplastic smooth muscle cells are a frequent component of endometriosis in the rectovaginal pouch with nodular growth and may present diagnostic challenges. TRUS-FNA is a minimally invasive procedure that can provide an accurate diagnosis of endometriosis, even in this variant of deep infiltrating disease.

A Cytological Study of Oral Human Papillomavirus (HPV) Infection Among Electronic Cigarette Smokers in Al-Madinah Al-Munawara.

Objective This study aims to determine how electronic cigarette (e-cigarette) use contributes to the spread of the human papillomavirus (HPV) and to assess the potential cellular proliferative activity it may produce. Methodology In Madinah, a case-control study was conducted between October 2022 and March 2023. Two oral cytologic smear samples were collected from each of the 500 volunteers; 250 consumers of electronic cigarettes and 250 non-smokers each provided two samples. To detect cytological changes and HPV infection, these samples were stained using Papanicolaou and immunocytochemical techniques. Results Twelve (4.8%) of the electronic cigarettes exhibited cytological atypia, while only one (0.4%) of the nonsmokers' group did. Infection with the human papillomavirus (HPV) was detected in eight (3.2%) of the e-cigarette users, but it was only found in two (0.8%) of the nonsmokers (P ≤ 0.05). Conclusion Electronic cigarette smokingincreases the likelihood of contracting HPV and developing cytological atypia, both of which, if left untreated, can contribute to the development of precancerous and cancerous lesions in the mouth.

ORAL CARCINOMA IN A PATIENT WITH SYSTEMIC SCLEROSIS

Systemic sclerosis (SSc) is a rare autoimmune connective tissue disorder characterized by fibrosis, vasculopathy, and inflammation. SSc's disease-related characteristics include skin tightness, puffy fingers, open ulcers, and multi-organ involvement. Studies have also identified a higher risk for the development of malignancy in SSc patients. A 56-year-old woman with SSc presented an asymptomatic white plaque of 20 × 25 mm in the right lower lip. Medical history revealed a previous diagnosis of breast cancer and current diagnosis of colorectal cancer. An incisional biopsy was performed, and histological examination showed architectural and cytological atypia of the full epithelial thickness, consistent with those of a severe, in situ dysplasia/carcinoma. The patient was referred to oncology services. Early localized stage diagnosis of in situ carcinoma of the oral cavity brings more favorable prognosis with better overall management, especially in individuals with SSc who presented systemic overlapping complications. Funding: CAPES. Systemic sclerosis (SSc) is a rare autoimmune connective tissue disorder characterized by fibrosis, vasculopathy, and inflammation. SSc's disease-related characteristics include skin tightness, puffy fingers, open ulcers, and multi-organ involvement. Studies have also identified a higher risk for the development of malignancy in SSc patients. A 56-year-old woman with SSc presented an asymptomatic white plaque of 20 × 25 mm in the right lower lip. Medical history revealed a previous diagnosis of breast cancer and current diagnosis of colorectal cancer. An incisional biopsy was performed, and histological examination showed architectural and cytological atypia of the full epithelial thickness, consistent with those of a severe, in situ dysplasia/carcinoma. The patient was referred to oncology services. Early localized stage diagnosis of in situ carcinoma of the oral cavity brings more favorable prognosis with better overall management, especially in individuals with SSc who presented systemic overlapping complications. Funding: CAPES.

Osteoid osteomas of the hands and feet: a series of 71 cases.

Osteoid osteomas typically arise in the long bones of extremities. Patients often report pain relieved by NSAIDS, and radiographic findings are often sufficient for diagnosis. However, when involving the hands/feet, these lesions may go unrecognized or misdiagnosed radiographically due to their small size and prominent reactive changes. The clinicopathologic features of this entity involving the hands and feet are not well-described. Our institutional and consultation archives were searched for all cases of pathologically confirmed osteoid osteomas arising in the hands and feet. Clinical data was obtained and recorded. Seventy-one cases (45 males and 26 females, 7 to 64 years; median 23 years) arose in the hands and feet, representing 12% of institutional and 23% of consultation cases. The clinical impression often included neoplastic and inflammatory etiologies. Radiology studies demonstrated a small lytic lesion in all cases (33/33), the majority of which had a tiny focus of central calcification (26/33). Nearly, all cases demonstrated cortical thickening and/or sclerosis and perilesional edema which almost always had an extent two times greater than the size of the nidus. Histologic examination showed circumscribed osteoblastic lesions with formation of variably mineralized woven bone with single layer of osteoblastic rimming. The most common growth pattern of bone was trabecular (n = 34, 48%) followed by combined trabecular and sheet-like (n = 26, 37%) with only 11 (15%) cases presenting with pure sheet-like growth pattern. The majority (n = 57, 80%) showed intra-trabecular vascular stroma. No case showed significant cytology atypia. Follow up was available for 48 cases (1-432 months), and 4 cases recurred. Osteoid osteomas involving the hands and feet follow a similar age and sex distribution as their non-acral counterparts. These lesions often present with a broad differential diagnosis and may initially be confused with chronic osteomyelitis or a reactive process. While the majority of cases have classic morphologic features on histologic exam, a small subset consists solely of sheet-like sclerotic bone. Awareness that this entity may present in the hands and feet will help pathologists, radiologists, and clinicians accurately diagnose these tumors.

Bladder Postoperative Spindle Cell Nodule: Malignant Mimicry in the Postoperative Setting

Bladder Postoperative Spindle Cell Nodule: Malignant Mimicry in the Postoperative Setting

Clinico-cytopathological subcategorization in thyroid nodules of atypia of undetermined significance/follicular lesion of undetermined significance using the TIRADS and Bethesda classifications.

Bethesda category III - atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is a heterogeneous class of the Bethesda system for thyroid nodules. In order to clarify the therapeutic road for clinicians, this category was subclassified based on the cytopathological features. In this study, we evaluated the risk of malignancy, surgical outcome, demographic characteristics, and correlation of ultrasound features with the final outcome in patients with thyroid nodules based on AUS/FLUS subclassification. After evaluating 867 thyroid nodules from three different centers, 70 (8.07%) were initially diagnosed as AUS/FLUS. The cytopathologists re-interpreted the FNA samples and subclassified them into five subcategories: architectural atypia, cytologic atypia, cytologic and architectural atypia, and Hürthle cell AUS/FLUS, and atypia, which was not specified. Based on the suspicious ultrasound features, an appropriate ACR TI-RADS score was allocated to each nodule. Finally, the malignancy rate, surgical outcomes, and ACR TI-RADS scores were evaluated among Bethesda category III nodules. Among the 70 evaluated nodules, 28 (40%) were subclassified as Hürthle cell AUS/FLUS, 22 (31.42%) as cytologic and architectural atypia, 8 (11.42%) as architectural atypia, 7 (10%) as cytologic atypia, and 5 (7.14%) as atypia which was not specified. The overall malignancy rate was 34.28%, and the architectural atypia and Hürthle cell nodules displayed lower malignancy compared to other groups (P-Value<0.05). Utilizing ACR TI-RADS scores showed no statistical significance between Bethesda III subcategorization and ACR TI-RADS scores. However, ACR TI-RADS can be a reliable predictor for Hürthle cell AUS/FLU nodules. ACR TI-RADS helps evaluate malignancy only in the Hürthle cell AUS/FLUS subcategory of AUS/FLUS. Besides, cytopathological reporting based on the suggested AUS/FLUS subclassification could help clinicians take appropriate measures to manage thyroid nodules.

Recurrent PAK2 rearrangements in poroma with folliculo-sebaceous differentiation.

Poroma is a benign adnexal neoplasm with differentiation towards the upper portion of the sweat gland apparatus. In 2019, Sekine etal. demonstrated recurrent YAP1::MAML2 and YAP1::NUTM1 fusion in poroma and porocarcinoma. Follicular, sebaceous and/or apocrine differentiation has been reported in rare cases of poroma and whether these tumours constitute a variant of poroma or represent a distinctive tumour is a matter to debate. Herein we describe the clinical, immunophenotypic, and molecular features of 13 cases of poroma with folliculo-sebaceous differentiation. Most of the tumours were located on the head and neck region (n = 7), and on the thigh (n = 3). All presented were adults with a slight male predilection. The median tumour size was 10 mm (range: 4-25). Microscopically, lesions displayed features of poroma with nodules of monotonous basophilic cells associated with a second population of larger eosinophilic cells. In all cases, ducts and scattered sebocytes were identified. Infundibular cysts were present in 10 cases. In two cases high mitotic activity was noted, and in three cases cytologic atypia and areas of necrosis were identified. Whole transcriptome RNA sequencing demonstrated in-frame fusion transcripts involving RNF13::PAK2 (n = 4), EPHB3::PAK2 (n = 2), DLG1::PAK2 (n = 2), LRIG1::PAK2 (n = 1), ATP1B3::PAK2 (n = 1), TM9SF4::PAK2 (n = 1), and CTNNA1::PAK2 (n = 1). Moreover, fluorescence in situ hybridisation (FISH) analysis revealed PAK2 rearrangement in an additional case. No YAP1::MAML2 or YAP1::NUTM1 fusion was detected. Recurrent fusions involving the PAK2 gene in all analysed poroma with folliculo-sebaceous differentiation in this study confirms that this neoplasm represents a separate tumour entity distinct from YAP1::MAML2 or YAP1::NUTM1 rearranged poromas.

Cytopathology of salivary gland myoepithelial carcinoma: A study of 13 cases and review of the literature

Myoepithelial carcinoma (MECA) is an infrequently recognized salivary gland (SG) neoplasm that commonly develops within a preexisting pleomorphic adenoma (MECA ex PA). Fine-needle aspiration (FNA) biopsy reports of this neoplasm are largely restricted to small series and single case reports. Our cytopathology files were searched for examples of SG MECA/MECA ex PA having confirmatory histopathologic verification. Conventional FNA biopsy smears were performed, and exfoliative specimens processed using standard techniques. Thirteen cases from 9 patients (M:F = 3.5:1; age range: 36 to 95 years, mean age = 60 years) met inclusion criteria. FNA biopsy sites included parotid gland (4), trunk (2), scalp (2), and neck (2). Exfoliative specimens included pleural fluid (1), bronchial brushing (1), and bronchoalveolar lavage (1). Most cases were metastatic deposits (8; 62%), 4 were primary neoplasms, and 1 a local recurrence. FNA diagnoses were MECA ex PA (6; 46%), myoepithelial neoplasm (2), PA (2), basaloid neoplasm (1), atypical myoepithelial cells (1), and myxoma (1). Ancillary testing in 2 cases showed positive staining for myoepithelial markers. Cytologic features were that of a low-grade neoplasm composed principally of epithelioid/polygonal cells exhibiting minimal if any cytologic atypia. Myxoid and chondromyxoid stroma was often the dominant feature in MECA ex PA aspirates. In the primary setting, a cytologic diagnosis of MECA/MECA ex PA is extremely challenging if at all possible. Due to overwhelming amounts of stroma, the diagnosis may be challenging in some cases of metastatic MECA ex PA.

Localized Endometrial Proliferations of Pregnancy are Clonal Glandular Outgrowths Characterized by PTEN Loss and PIK3CA Pathogenic Variants

Gestational endometrium can demonstrate a spectrum of atypical but benign changes. One such lesion is localized endometrial proliferation of pregnancy (LEPP), first described in a series of 11 cases. To understand its biological and clinical importance, we explore the pathologic, immunophenotypic, and molecular features of this entity. Nine cases of LEPP identified in 15 years were retrieved from departmental archives and reviewed. Immunohistochemistry and next-generation sequencing using a comprehensive 446-gene panel were performed when the material was available. Eight cases were identified in curettage specimens performed after first-trimester pregnancy loss, and 1 in the basal plate of a mature placenta. The mean patient age was 35 (range 27–41) years. The mean lesion size was 6.3 (range 2–12) mm. Architectural patterns, often coexisting in the same case, included cribriform (n = 7), solid (n = 5), villoglandular (n = 2), papillary (n = 2), and micropapillary (n = 1). Cytologic atypia was mild in 7 cases and moderate in 2. Mitotic activity was low (up to 3 per 2.4 mm2). All lesions were associated with neutrophils. Background Arias–Stella phenomenon was present in 4 cases. Immunohistochemistry was performed in 7 LEPP, all of which demonstrated wildtype p53, retained MSH6 and PMS2, membranous beta-catenin, and positive estrogen receptor (mean 71%) and progesterone receptor (mean 74%). All were negative for p40 except 1 case (focal weak positivity). PTEN was markedly reduced in background secretory glands in all cases; in 5/7, LEPP foci showed a complete absence of PTEN expression. PIK3CA pathogenic variants were identified in 4/4 cases sequenced; 3/4 had inactivating PTEN mutations. Follow-up, available in 8 patients (mean length = 51 months, range 7–161), was conservative with observation only and showed no persistence or adverse outcomes. LEPP is characterized by intraglandular cribriform/solid architecture, positive estrogen receptor/progesterone receptor, PTEN loss, and PIK3CA and PTEN mutations. Although our findings indicate that LEPP is neoplastic, for now, we advise against diagnosing LEPP as endometrial carcinoma or hyperplasia because LEPP has a particular clinicopathologic context (concurrent gestation), distinct morphology (purely intraepithelial complex growth), and indolent outcome. Thus, it should be distinguished from endometrial intraepithelial neoplasia and carcinoma for which therapeutic interventions are indicated.

Sensitivity of endoscopic ultrasound-guided fine-needle aspiration cytology and biopsy for a diagnosis of pancreatic ductal adenocarcinoma: A comparative analysis.

The utility of endoscopic ultrasound fine-needle aspiration cytology (EUS-FNAC) or endoscopic ultrasound fine-needle aspiration biopsy (EUS-FNAB) for diagnosis of small and large pancreatic ductal adenocarcinomas (PDACs) remains in question. We addressed this by analyzing 97 definitively diagnosed cases of PDAC, for which both EUS-FNAC and EUS-FNAB had been performed. We subclassified the 97 solid masses into small (n = 35) or large (n = 62) according to the maximum tumor diameter (<24 mm or ≥24 mm) and compared the diagnostic sensitivity (truly positive rate) of EUS-FNAC and of EUS-FNAB for small and large masses. Diagnostic sensitivity of EUS-FNAC did not differ between large and small masses (79.0% vs. 60.0%; p = 0.0763). However, the diagnostic sensitivity of EUS-FNAB was significantly higher for large masses (85.5% vs. 62.9%; p = 0.0213). Accurate EUS-FNAC-based diagnosis appeared to depend on the degree of cytological atypia of cancer cells, which was not associated with quantity of cancer cells. The accuracy of EUS-FNAB-based diagnosis appeared to depend on cancer cell viability in large masses and cancer volume in small masses. Based on the advantages or disadvantages in each modality, both modalities play an important role in the qualitative diagnosis of PDAC as a complementary procedure.

Thymic Parenchymal Hyperplasia

Thymic hyperplasia is a rare condition generally caused by lymphoid follicular hyperplasia associated with autoimmune disorders. True thymic parenchymal hyperplasia unassociated with lymphoid follicular hyperplasia is extremely rare and may give rise to difficulties in diagnosis. We have studied 44 patients with true thymic hyperplasia (38 females and 6 males) aged 7 months to 64 years (mean, 36 years). Eighteen patients presented with symptoms of chest discomfort or shortness of breath; in 20 patients, the lesions were discovered incidentally. Imaging studies demonstrated enlargement of the mediastinum by a mass lesion suspicious for malignancy. All patients were treated with complete surgical excision. The tumors measured from 3.5 to 24 cm (median, 10 cm; mean, 10.46 cm). Histologic examination showed lobules of thymic tissue displaying well-developed corticomedullary architecture, with scattered Hassall corpuscles separated by mature adipose tissue and bounded by a thin fibrous capsule. No cases showed evidence of lymphoid follicular hyperplasia, cytologic atypia, or confluence of the lobules. Immunohistochemical studies showed a normal pattern of distribution for keratin-positive thymic epithelial cells against a background rich in CD3/TdT/CD1a+ lymphocytes. Twenty-nine cases had an initial clinical or pathological diagnosis of thymoma or thymoma vs thymic hyperplasia. Clinical follow-up in 26 cases showed that all patients were alive and well between 5 and 15 years after diagnosis (mean, 9 years). Thymic parenchymal hyperplasia causing significant enlargement of the normal thymus that is sufficient to cause symptoms or worrisome imaging findings should be considered in the differential diagnosis of anterior mediastinal masses. The criteria for distinguishing such lesions from lymphocyte-rich thymoma are presented.