Thymic Squamous Cell Carcinoma Research Articles

Analysis of Clinical Characteristics and Prognosis of 18 Cases Unresectable Stage IV Thymic Squamous Cell Carcinoma

Analysis of Clinical Characteristics and Prognosis of 18 Cases Unresectable Stage IV Thymic Squamous Cell Carcinoma

AB017. Circulating exosomal miRNAs as potential diagnostic and prognostic biomarkers for thymic squamous cell carcinoma

AB017. Circulating exosomal miRNAs as potential diagnostic and prognostic biomarkers for thymic squamous cell carcinoma

Whole Liver Radiotherapy for Multiple Liver Metastases in Thoracic Malignancies

Liver metastases (LM) are common in advanced thoracic cancer patients with dismal oncological outcomes. Even in the modern era of novel systemic therapy, LM led to a 21% increased mortality risk compared with those without. Options for progressive multiple LM after systemic therapy are limited. Therefore, a different treatment modality is urgently needed to overcome such a predicament. Herein, we renovate the classical whole liver radiotherapy (WLRT) and evaluate its efficacy and safety in treating thoracic cancer patients with progressive multiple LM. Patients with lung or thymic cancer who had multiple LM treated by WLRT between 2018 and 2022 were enrolled. Radiotherapy (RT) was delivered with a median dose of 24 Gy (range 8-25 Gy) in 8 fractions (range 1-16) at the discretion of treating physicians. Overall survival (OS) and cumulative incidence of intrahepatic progression were calculated from the completion of WLRT till death or progression by Kaplan-Meier and competing risk analyses, respectively. Twenty-four patients were enrolled in this retrospective study. Eleven patients (46%) had lung adenocarcinoma, of which nine patients had oncogenic mutations. Six patients (25%) had small cell lung cancer (SCLC), four patients (17%) had thymic squamous cell carcinoma (SqCC), two patients (8%) had lung SqCC, and one patient (4%) had mixed histology. Eighteen patients (75%) were under systemic therapy treatment before the diagnosis of LM, and fifteen (63%) received LM biopsy. The median time from the diagnosis of LM to WLRT was 7.5 months (range, 0.5-33.9 months). Eleven patients (46%) had concurrent RT and systemic therapy. With a median follow-up of 3.1 months, the 3-, 6- and 12-month OS were 57%, 38%, and 15%, respectively. After adjusting death as a competing risk, the cumulative incidence of LM progression at 3, 6, and 12 months were 10%, 19%, and 44%, respectively. Within three months after the completion of RT, one patient (4%) had grade 5 radiation-induced liver disease (RILD), one patient (4%) had grade 4 abnormal liver function test (LFT), three patients (13%) had grade 3 abnormal LFT, and twelve patients (50%) had ≤ grade 2 abnormal LFT. The patient who had Gr.5 RILD expired 51 days after the completion of RT with 24 Gy in 8 fractions concurrently with topotecan. He had primary SCLC with viral hepatitis B. His LFT was around the normal upper limit before WLRT. WLRT provided favorable intrahepatic control with acceptable radiation-related toxicities and could be considered a treatment option for patients with progressive LM under systemic therapy. Further investigation with a larger cohort is warranted to identify patients at a high risk of developing severe RILD.

Survival nomogram for patients with thymic squamous cell carcinoma, based on the SEER database and an external validation cohort

ObjectiveThis study aimed to construct a nomogram to effectively predict the 3 years and 5 years overall survival of patients with thymic squamous cell carcinoma (TSCC).MethodFrom 2000 to 2019, a total of 355 patients with TSCC were enrolled in our research from the Surveillance, Epidemiology, and End Results (SEER) database and used as the training cohort. 106 patients were included from the Zhejiang Cancer Hospital, for the external validation cohort. A nomogram was constructed based on the risk factors affecting prognosis using a Cox proportional hazards regression model. The discrimination and calibration of the nomogram were evaluated by C-index and curve of calibration. The two cohorts were divided into low-risk and high-risk subgroups based on the median risk score.ResultsAge (p = 0.002), stage (p = 0.003), surgery therapy (p < 0.001), and radiotherapy (p = 0.030) were the independent prognostic factors for overall survival and were incorporated in the prognostic model. The discrimination of the nomogram revealed a good prognostic accuracy and clinical applicability as indicated by C-index values of 0.696 (95% confidence interval [CI] 0.676–0.716) and 0.717 (95% CI 0.640–0.794) for the training cohort and external validation cohort, respectively. In addition, the two cohorts were divided into a high-risk group and a low-risk group according to the median risk score. Significant differences in overall survival were observed between the high-risk and low-risk groups in the training (p < 0.0001) and external validation cohort (p < 0.0001).ConclusionWe developed a nomogram to predict 3- and 5 year survival rate for TSCC. This nomogram provides a convenient and reliable tool for assessing the condition of patients with TSCC and assisting clinicians in making decisions.

Identification of predictors of long-term survival and prognostic outcomes in thymic squamous cell carcinoma: A real-world study.

Although thymic squamous cell carcinoma (TSCC) is among the most prevalent forms of thymic carcinoma, there are relatively few studies on this tumor type, and its staging, optimal treatment strategies, and relevant prognostic factors remain controversial. The present study analyzed 79 patients diagnosed with TSCC between January 2008 and January 2021. Kaplan-Meier curves and Cox univariate and multivariate regression analyses were used to explore factors associated with overall survival (OS) and progression-free survival (PFS) in the overall patient cohort and patient subgroups stratified according to the TNM stage. Time-dependent receiver operating characteristic (ROC) analyses were used to compare the TNM and Masaoka systems as predictors of patient prognosis. The 5- and 10-year OS rates in this study were 65.5% and 49.4%, respectively, with corresponding 5- and 10-year PFS rates of 52.3% and 37.9%. Survival outcomes were better for patients with early-stage disease (p < 0.001) and patients that underwent surgical treatment (p < 0.001). Neither extent of resection (p = 0.820) nor the surgical approach (p = 0.444) influenced patient survival. In individuals with advanced disease, all forms of adjuvant therapy including radiotherapy (p = 0.021), chemotherapy (p = 0.035), and chemoradiation (p = 0.01) significantly improved patient PFS, but only adjuvant chemoradiotherapy improved patient OS (p = 0.035). When predicting the patient survival outcomes, the TNM system was slightly superior to the Masaoka system (area under the ROC curve [AUC] at 5 years: OS, 0.742 vs. 0.723; PFS, 0.846 vs. 0.816). TSCC is an orphan malignancy with a poor prognosis. TNM staging may be superior to Masaoka staging as a predictor of TSCC patient prognosis. Surgery is the mainstay of TSCC treatment. Video-assisted thoracoscopy (VATS) should be considered for selected patients. Multimodal therapy was associated with excellent results for patients with advanced TNM stage, particularly when surgery was accompanied by adjuvant chemoradiation.

Histogenetic and disease-relevant phenotypes in thymic epithelial tumors (TETs): The potential significance for future TET classification.

Thymic epithelial tumors (TETs) encompass morphologically various subtypes. Thus, it would be meaningful to explore the expression phenotypes that delineate each TET subtype or overarching multiple subtypes. If these profiles are related to thymic physiology, they will improve our biological understanding of TETs and may contribute to the establishment of a more rational TET classification. Against this background, pathologists have attempted to identify histogenetic features in TETs for a long time. As part of this work, our group has reported several TET expression profiles that are histotype-dependent and related to the nature of thymic epithelial cells (TECs). For example, we found that beta5t, a constituent of thymoproteasome unique to cortical TECs, is expressed mainly in type B thymomas, for which the nomenclature of cortical thymoma was once considered. Another example is the discovery that most thymic carcinomas, especially thymic squamous cell carcinomas, exhibit expression profiles similar to tuft cells, a recently discovered special type of medullary TEC. This review outlines the currently reported histogenetic phenotypes of TETs, including those related to thymoma-associated myasthenia gravis, summarizes their genetic signatures, and provides a perspective for the future direction of TET classification.

Intrathyroid thymic carcinoma: clinicopathological features and whole exome sequencing analysis.

Intrathyroid thymic carcinoma (ITC) is a rare malignant tumour. We present nine cases of ITC that were analysed by immunohistochemical staining, of which five were analysed using whole exome sequencing (WES). These cases included six women and three men with an age range of 31-66years. The average postoperative follow-up term was 37.8months (range, 7-95months), and all patients survived well except for one case with lung metastasis. Microscopically, ITC showed solid islands of tumour cells separated by fibrous connective tissue containing lymphocytes and other inflammatory cells. Tumour cells strongly expressed Ckpan (AE1/AE3), P63, and CD117. And all cases but one were positive for CD5. The median value of Ki-67 was 32% (range 10-60%). We observed partial positivity of Syn and CgA in only one case. ITC shares morphological and immunohistochemical similarities with thymic squamous cell carcinoma. In situ hybridization of EBER showed negative results. All cases were microsatellite stable, and the tumour mutational burden of the 5 cases was all < 1 mutations/Mb. WES showed higher mutation rates for N4BP1 (2/5), and many genetic alterations were related to the NF-kB signalling pathway, which is crucial for insight into the molecular mechanisms of the occurrence and development of ITC.

CALML5 is a novel diagnostic marker for differentiating thymic squamous cell carcinoma from type B3 thymoma.

Thymic squamous cell carcinoma and type B3 thymoma are primary neoplasms of the anterior mediastinum that are sometimes difficult to differentiate from one another histologically. However, only a few immunohistochemical markers are available for the differential diagnosis. The purpose of this study was to discover a novel marker for differentiating between thymic squamous cell carcinoma and type B3 thymoma. We used histological samples of thymic carcinomas (n=26) and type B3 thymomas (n=38) which were resected between 1986 and 2017. To search for candidates of differential markers, gene expression levels were evaluated in samples using promoter analysis by cap analysis of gene expression (CAGE) sequencing. Promoter level expression of CALML5 genes was significantly higher in thymic carcinomas than in type B3 thymomas. We further validated the results of the CAGE analysis in all 26 thymic carcinomas and 38 type B3 thymomas by immunohistochemistry (IHC). CALML5 was strongly expressed in the cytoplasm in 19 of 26 cases with thymic carcinoma, whereas positivity at the protein level was shown in two of 38 type B3 thymomas. Thus, the sensitivity (73.1%) and specificity (94.7%) of CALML5 as markers for immunohistochemical diagnosis of thymic carcinoma were extremely high. We identified CALML5 as a potential marker for differentiating thymic squamous cell carcinoma from type B3 thymoma. It is assumed that future clinical use of CALML5 may improve the diagnostic accuracy of differentiating between these two diseases.

The clinicopathological significance of thymic epithelial markers expression in thymoma and thymic carcinoma

BackgroundThe classification of thymomas is based on the morphology of epithelial tumor cells and the proportion of lymphocytes. Type A thymomas are composed of the spindle or oval tumor epithelial cells. Tumor cells of B thymomas are epithelioid-shaped with increasing atypia. Type AB thymomas have the features of epithelial tumor cells of A and B thymomas. The diagnosis can be difficult because of the complex morphology. Some novel thymic epithelial markers have been reported in several preclinical studies, but they have not been applied to clinical practice. Here, we investigated the expression of 3 cortical and 3 medullary markers, which are thymoproteasome-specific subunit β5t (β5t), thymus-specific serine protease 16 (PRSS16), cathepsin V, autoimmune regulator (AIRE), CD40 and claudin-4.MethodsImmunohistochemistry was used to analyze 53 cases of thymomas and thymic squamous cell carcinomas (TSCC), aiming to explore the expression of cortical and medullary epithelial markers and their correlation with histological classification, Masaoka-Koga stage, and prognosis.ResultsOur results found that for cortical epithelial markers the expression of β5t, PRSS16, and cathepsin V was higher in type AB and B thymomas than in micronodular thymoma with lymphoid stroma (MNT), and we observed a dramatic increase of β5t and PRSS16 expression in type AB compared to type A thymomas. In medullary epithelial markers, the expression of AIRE was higher in type A than in B3 thymomas. CD40 and β5t expression were associated with the Masaoka-Koga stage. High cathepsin V expression was related to a good prognosis and a longer progression-free survival.ConclusionThis is the first comprehensive analysis of the role of thymic cortical and medullary epithelial markers as biomarkers for differential diagnosis and prognosis in thymic tumors. Thymic medullary epithelial immunophenotype was found to exhibit in type A, MNT, and TSCC. Type B thymomas primarily exhibited a cortical epithelial immunophenotype. Type AB thymomas showed cortical, medullary, or mixed corticomedullary epithelial immunophenotype. Our results demonstrated that thymic cortical and medullary epithelial markers including β5t, PRSS16, cathepsin V, and AIRE could be used as ancillary markers in the diagnosis and prognosis of thymic epithelial tumors.

Insulinoma-associated-1 (INSM1) expression in thymic squamous cell carcinoma.

Thymic squamous cell carcinoma (TSC) presents distinct immunohistochemical features with its expression of CD5 and CD117, both of which are rarely expressed in squamous cell carcinoma in other organs. We found insulinoma-associated-1 (INSM1) expression in some TSCs; thus, a series of thymic tumors were examined retrospectively. Using surgically resected thymic tumors (TSC, n = 35; thymic atypical carcinoid [TAC], n = 4; and thymoma, n = 112) and non-neoplastic thymic tissue (n = 26), we evaluated immunohistochemically the expressions of INSM1, ASCL1, SOX2, NE markers (synaptophysin, chromogranin A, and CD56), and conventional TSC markers (CD5 and CD117). INSM1 was expressed in 22 TSCs (63%), whereas the positive frequencies of synaptophysin, chromogranin A, and CD56 were limited to 13, 10, and 1 cases, respectively. The discordance was highly contrasted with concordantly positive TACs. INSM1 and NE makers were rarely expressed in thymomas. INSM1 expression in TSCs was also associated with CD5 expression, which was significantly less frequent in INSM1-negative TSCs. INSM1, ASCL1, and SOX2 expressions were correlated with one another, but none of the single transcription factors or their combinations is associated with NE expression. The non-neoplastic medullary thymic epithelium was dispersedly positive for INSM1, particularly around Hassall's corpuscles. Despite positive INSM1, a significant decrease in the frequency of NE maker expression may present as a diagnostic pitfall in TSCs. Furthermore, the discordance, which was inherent in the non-neoplastic thymic epithelium, might be a characteristic feature in TSCs.

Modified subcostal arch xiphoid thoracoscopic expanded thymectomy for thymic carcinoma: a case report and review of literature

Thymic neoplasms are a relatively uncommon tumor, with the anterior mediastinum being the most common. Median sternotomy is the procedure of choice for the treatment of thymomas. With the advent of thoracoscopy, an increasing number of countries are adopting the right thoracic approach for the treatment of thymomas, but there are still no clear surgical standards or modalities to treat thymic carcinoma. We propose a modified subxiphoid subcostal arch thoracoscopic enlarged thymectomy to treat thymic carcinoma based on various reviews. We have also reviewed the relevant literature on the subject of evidence-based medicine. The evaluation of CD70 in combination with CD5 and CD117 or preferentially expressed antigen in melanoma in combination with CD5 and CD117 may help to diagnose thymic squamous cell carcinoma (TSCC) more accurately. The modified thoracoscopic expanded thymic resection under the costal arch of the xiphoid process is not only suitable for TSCC but also for thymic cyst, thymoma, locally invasive thymoma, and thymic carcinoma.

Skeletal muscle and related protein expression as prognostic factors in thymic squamous cell carcinoma.

BackgroundSarcopenia and its marker, the psoas muscle index (PMI), have attracted attention as prognostic factors for various types of cancers. The fragile X-related 1 (FXR1) gene is highly expressed in myocytes, and FXR1 overexpression is a candidate biomarker for poor survival in several types of cancers. Thymic squamous cell carcinoma (TSQCC) is rare, and no studies assessing its prognostic factors, particularly in terms of skeletal muscle mass and FXR1 expression, are available.MethodsWe retrospectively investigated the prognostic significance of PMI in 34 patients who underwent TSQCC resection, considering the status of FXR1 and tumor programmed death-ligand 1 (PD-L1). PMI was calculated from the bilateral psoas muscle using preoperative computed tomography (CT). Patients were divided into two groups: low PMI (<58.2%, n=17) and normal PMI (≥58.2%, n=17). Immunohistochemical analysis was performed to determine the FXR1 and PD-L1 expression levels.ResultsLow PMI was significantly associated with worse overall survival (OS) (5-year survival rate; 86% vs. 100%; P=0.026) and marginally associated with worse disease-free survival (DFS) (5-year survival rate; 39% vs. 66%; P=0.090) compared with normal PMI. The immunohistochemical analysis revealed that the FXR1 intensity score (0–1+: 6% vs. 0%; 2+–3+: 94% vs. 100%; P=0.31), median FXR1 distribution (95% vs. 90%; P=0.63), and PD-L1 status (high: 47% vs. 59%; P=0.49) were not significantly different between the two groups.ConclusionsOur findings suggest that PMI might be considered as a potential prognostic factor in TSQCC and that FXR1 is widely expressed regardless of the PMI status. Skeletal muscle mass may play a role in the prognosis of TSQCC.

Thymic squamous cell carcinoma lurking in a growing large cyst: A case report

An 81-year-old man was admitted for resection of an asymptomatic left anterior mediastinal tumor. Chest computed tomography showed that a small, homogeneous lesion had grown to a large, cystic lesion (80 mm) over a 5-year period. The cystic tumor was removed with adherent structures such as the left upper pulmonary parenchyma and lower part of the left innominate vein via median sternotomy with assistance from a left thoracoscopic procedure. Macroscopically, a solid tumor was located within the large multilocular cyst. The pathological diagnosis was cystic squamous cell carcinoma (12 mm), which had not infiltrated any surrounding organs. The patient has remained well without recurrence as of 4 years postoperatively.

Challenges in diagnosis of thymic carcinoma

Thymic Carcinoma (TC) is a rare tumor among the epithelial tumors of the thymus with a challenging diagnosis for pathologists. A case report, a 55-year-old male patient complained of coughing, chest pain, and intermittent shortness of breath for 2 weeks before being referred. Patient underwent radiological examination, surgery, histopathological examination and immunohistochemical examination to reach the definitive diagnosis. The histopathological examination of Thymic Squamous Cell Carcinoma was established with immunohistochemical examination.

CD70 in Thymic Squamous Cell Carcinoma: Potential Diagnostic Markers and Immunotherapeutic Targets.

CD70 – a ligand protein of CD27 on lymphocytes – is expressed in a large spectrum of malignancies. It is an attractive target for antibody-based therapy and several clinical trials are currently being conducted. However, there is no evidence regarding the expression of CD70 and its relationship with expression of programmed death ligand-1 (PD-L1) and CD27+ tumor-infiltrating lymphocytes (TIL) in formalin-fixed paraffin-embedded (FFPE) tissues of thymic tumors. FFPE tissues of thymic squamous cell carcinoma (TSCC) (operative specimens, n = 31; biopsy specimens, n = 11), thymoma (n = 60), thymic carcinoid (n = 3), and lung squamous cell carcinoma (LSCC) (n = 30) were analyzed immunohistochemically. Immunoreactivity for CD70 was semi-quantitatively scored according to the proportion of positive tumor cells. Moreover, the densities of CD27-positive intratumoral TIL (iTIL) and stromal TIL of TSCC were assessed and survival was compared. Most TSCC cases (87%; 27/31) were CD70-positive. In contrast, all thymoma and thymic carcinoid cases were CD70-negative. In LSCC cases, CD70-positivity was significantly lower than TSCC cases (20%; 6/30). Biopsy and resected specimens obtained from the same patients demonstrated a consistent staining pattern (6/6 patients). The proportion of CD70-positive TSCC was comparable with those of CD5 (87%) and CD117 (90%). Correlation between CD70 and PD-L1 expression score was observed. There was no significant difference in survival between the CD70-high and CD70-low expression groups. Meanwhile, patients with CD27-positive iTIL-high tumors exhibited better survival than those with iTIL-low tumors. This tendency was weaker in the CD70-high subset. CD70 immunohistochemistry is useful in diagnosing TSCC. CD70 may prevent anti-tumor immunity via CD27. Immunotherapy targeting the CD70–CD27 axis may be a promising option for the treatment of TSCC.

POU2F3 beyond thymic carcinomas: expression across the spectrum of thymomas hints to medullary differentiation in type A thymoma.

The thymic medulla comprises various cell types, including tuft cells that are involved in innate immunity. We recently reported that in Western cohorts of patients, most thymic squamous cell carcinomas (TSQCCs), in contrast to thymomas, exhibit strong and extensive expression of tuft cell markers, including the tuft cell master regulator, POU2F3. On closer inspection of 94 thymomas that cover the full spectrum of thymoma histotypes, we now find by immunohistochemistry that approximately half of types A, AB, and B1 thymomas contain small numbers (< 10%) of cells expressing POU2F3, while most types B2 and B3 thymomas do not (p < 0.05). Further, in rarer types A and AB thymomas with adenoid growth pattern, POU2F3( +) cells formed aggregates and co-expressed KIT, as did the tumor cells in 100% (9/9) of TSQCCs expressing POU2F3. However, the expression of another tuft cell marker, L1CAM, still distinguished TSQCC from the spectrum of thymomas that were all L1CAM-negative. This study is the first to demonstrate the high frequency of POU2F3 expression in an Asian cohort of TSQCCs. The common occurrence of scattered POU2F3( +) cells in types A and AB thymomas hints at their variable degree of medullary differentiation and supports the historical hypothesis of the medullary nature of type A thymomas. Immunohistochemistry of L1CAM may be a valuable tool to differentiate TSQCCs from thymomas.

Transcriptomic and Mutational Analysis Discovering Distinct Molecular Characteristics Among Chinese Thymic Epithelial Tumor Patients.

IntroductionThymic epithelial tumors (TETs) are malignancies arising from the epithelium of the thymic gland, rare but with relatively favorable prognosis. TETs have different pathological subtypes: thymomas and thymic carcinoma, and they show different clinical characteristics regarding prognosis, pathology, and molecular profiles, etc. Although some studies have investigated the pathogenesis of TETs, more molecular data is still needed to further understand the underlying mechanisms among different TETs subtypes and populations.MethodsIn this study, we performed targeted gene panel sequencing and whole transcriptome sequencing on the tumor tissues from 27 Chinese TET patients, including 24 thymomas (A, AB, and B subtypes) and 3 thymic squamous cell carcinomas. We analyzed the genetic variations and differentially expressed genes among multiple TET subtypes. Moreover, we compared our data with the published The Cancer Genome Atlas (TCGA) TET data on both the genetic and transcriptomic levels.ResultsCompared with the TCGA TET genomic data, we found that NF1 and ATM were the most frequently mutated genes (each with a frequency of 11%, 3/27). These mutations were not mutually exclusive, since one B1 thymoma showed mutations of both genes. The GTF2I mutation was mainly enriched in subtype A and AB thymomas, consistent with the previous reports. RNA-seq results unveiled that the genes related to thymus development (FGF7, FGF10 and CLDN4) were highly expressed in certain TET subtypes, implicating that the developmental process of thymus might be linked to the tumorigenesis of these subtypes. We found high expression of CD274 (PD-L1) in B2 and B3 thymoma samples, and validated its expression using immunohistochemistry (IHC). Based on the expression profiles, we further established a machine learning model to predict the myasthenia gravis status of TET patients and achieved 90% sensitivity and 70.6% specificity in the testing cohort.ConclusionThis study provides the first genomic and transcriptomic analysis of a Chinese TET cohort. The high expression of genes involved in thymus developmental processes suggests the potential association between tumorigenesis of TETs and dysregulation of developmental pathways. The high expression of PD-L1 in B2 and B3 thymomas support the potential application of immunotherapy on certain thymoma subtypes.

Thymic squamous cell carcinoma mimicking lymphoma on 68Ga-FAPI PET/CT.

Thymic squamous cell carcinoma mimicking lymphoma on 68Ga-FAPI PET/CT.

Long-term survival in thymic carcinoma with postoperative pleural dissemination

BackgroundWe report a patient with thymic squamous cell carcinoma who underwent multiple rounds of surgical resection and definitive radiotherapy for both primary tumor and postoperative recurrence. However, the patient remains well and healthy 18 years after initial diagnosis. Since long-term survival after postoperative recurrence of thymic carcinoma is extremely rare, we also present her immunohistochemical staining results, which suggested indolent disease.Case presentationA 42-year-old woman with thymic squamous cell carcinoma underwent en bloc resection of the tumor and thymus gland. Pleural dissemination was noted in the right thoracic cavity 3, 10, and 16 years postoperatively. Where possible, the nodules were resected surgically: during the postoperative 3rd and 16th years. Definitive radiotherapy was administered for all nodules that could not be excised during the postoperative 3rd and 10th years. Disease-free survival is 25 months.ConclusionsLocal control of pleural dissemination may be beneficial in the treatment of postoperative recurrence of thymic carcinoma in limited cases of indolent disease.

Differentiating thymoma, thymic carcinoma and lymphoma based on collagen fibre patterns with T2- and diffusion-weighted magnetic resonance imaging.

The amount and distribution of intratumoural collagen fibre vary among different thymic tumours, which can be clearly detected with T2- and diffusion-weighted MR images. To explore the incidences of collagen fibre patterns (CFPs) among thymomas, thymic carcinomas and lymphomas on imaging, and to evaluate the efficacy and reproducibility of CFPs in differential diagnosis of thymic tumours. Three hundred and ninety-eight patients with pathologically diagnosed thymoma, thymic carcinoma and lymphoma who underwent T2- and diffusion-weighted MR imaging were retrospectively enrolled. CFPs were classified into four categories: septum sign, patchy pattern, mixed pattern and no septum sign. The incidences of CFPs were compared among different thymic tumours, and the efficacy and reproducibility in differentiating the defined tumour types were analysed. There were significant differences in CFPs among thymomas, thymic squamous cell carcinomas (TSCCs), other thymic carcinomas and neuroendocrine tumours (OTC&NTs) and thymic lymphomas. Septum signs were found in 209 (86%) thymomas, which differed between thymomas and any other thymic neoplasms (all p < 0.005). The patchy, mixed patterns and no septum sign were mainly seen in TSCCs (80.3%), OTC&NTs (78.9%) and thymic lymphomas (56.9%), respectively. The consistency of different CFP evaluation between two readers was either good or excellent. CFPs achieved high efficacy in identifying the thymic tumours. The CFPs based on T2- and diffusion-weighted MR imaging were of great value in the differential diagnosis of thymic tumours. • Significant differences are found in intratumoural collagen fibre patterns among thymomas, thymic squamous cell carcinomas, other thymic carcinomas and neuroendocrine tumours and thymic lymphomas. • The septum sign, patchy pattern, mixed pattern and no septum sign are mainly seen in thymomas (86%), thymic squamous cell carcinomas (80.3%), other thymic carcinomas and neuroendocrine tumours (79%) and thymic lymphomas (57%), respectively. • The collagen fibre patterns have high efficacy and reproducibility in differentiating thymomas, thymic squamous cell carcinomas and thymic lymphomas.