Atypical thymomas with squamoid and spindle cell features: clinicopathologic, immunohistochemical and molecular genetic study of 120 cases with long-term follow-up.

Thymomas are rare tumors characterized by a broad range of morphologic appearances that can sometimes give rise to difficulties for classification. We have studied a series of 120 thymoma patients in whom the tumors were characterized by sheets of atypical epithelial cells with squamoid and/or spindle cell features. They occurred in 63 men and 57 women and presented as a discrete mass in the anterior mediastinum measuring 2-23 cm (mean: 8.2 cm). Patients' ages ranged from 14 to 86 years (mean: 57.8) and most had symptoms referable to a mass lesion. 20 patients had myasthenia gravis or other autoimmune disorder. 76 cases were characterized by a predominant population of round to polygonal tumor cells while 32 cases were characterized by atypical oval or spindle cells. 12 cases showed mixed features and 16 cases showed the development of thymic carcinoma arising from thymoma. All cases were positive for p40/p63 and cytokeratin AE1/AE3. 23 cases were positive for CD5 (25%), and 13 for CD117 (14%). MIB1 showed a significant increase in proliferative activity (mean = 11.6%). Next generation sequencing in 47 cases did not disclose any variants amenable to current targeted therapies. Clinical follow up ranging from 2 to 29 years showed a progressive increase in aggressive behavior and fatality rate with advancing stage. Overall survival was 87% at 5 years, 67% at 10 years, and 23% at 20 years. Completeness of resection and staging were the most significant parameters for survival. The more aggressive tumors followed a protracted clinical course with multiple recurrences and metastases over a long period of time (mean = 19.8 years from time of initial relapse to death). Atypical thymomas are a distinct category of thymic epithelial neoplasm characterized by a slowly progressive clinical course with increased potential for metastases, transformation to a higher-grade malignancy, and fatal outcome in some cases.

Xanthomatous Thymoma: A Clinicopathologic and Immunohistochemical Study of 10 Cases.

OBJECTIVES: Ten cases of thymomas with an extensive xanthomatous component are presented. METHODS: Cases were identified during a review of more than 500 cases of thymomas. Histologic material from surgical resections was evaluated. RESULTS: The patients included five men and five women aged 47 to 64 years who had nonspecific symptoms. Grossly, all tumors were solid, measuring 2.5 to 4.5 cm. Eight tumors were encapsulated; two were minimally invasive. Histologically, the tumors showed varying histologies, all with an extensive xanthomatous component comprising 50% to 80% of the tumor. Immunohistochemical stains showed tumor cells positive for keratin and keratin 5/6 while the xanthomatous component was positive for CD68. Follow-up information showed nine patients remain alive with no recurrence. No follow-up information was obtained in one patient. CONCLUSIONS: The presence of an extensive xanthomatous component may pose difficulties in the interpretation of these tumors. This study highlights the importance of proper sampling and awareness of this unusual feature.

A practical approach to enrich intact tryptic N-glycopeptides through size exclusion chromatography and hydrophilicity (SELIC) using an acrylamide-agarose composite gel system.

Increasing researches proved that abnormal glycosylation is strongly correlated with many diseases. Specially, site-specific glycosylation and its associated heterogeneity are closely related to the function and activity of the glycoprotein. However, intact N-glycopeptide analysis still faces great challenges because the presence of highly abundant non-glycosylated peptides would suppress the ionization of lowly abundant glycopeptides. In the present study, we developed a practical intact tryptic N-glycopeptide enrichment method using acrylamide-agarose composite gel that combined the size exclusion chromatography and hydrophilic (named SELIC) effects, aimed to remove the detergent rapidly and effectively, as well as enrich intact N-glycopeptides while extracting peptides. This is a useful tool to facilitate the intact N-glycopeptides analysis of complex protein mixtures, particularly for samples that extracted from formalin-fixed and paraffin-embedded (FFPE) tissues by SDS. Using this method, we successfully identified 700 site-specific intact tryptic N-glycopeptides corresponding to 261 glycosylation sites on 191 glycoproteins from FFPE thymoma tissues.

[Metaplastic Thymoma;Report of a Case].

A 76-year-old man was referred to our division because of an abnormal shadow on chest computed tomography (CT). CT revealed a 20 mm nodule in the anterior mediastinum. Non-ivasive thymoma was suspected and thymomectomy and resection of right thymus was performed. The resected tumor was 25×25×13 mm in size. Pathologically the tumor was composed with polygonal cell components and spindle cell components, partially invading surrounding tissue. Cytokeratin AE1/3 and epithelial membrane antigen (EMA) were strongly positive, and the pathological diagnosis was biphasic, metaplastic thymoma.

Undifferentiated thymic carcinoma with intracranial metastasis in a two-year-old.

Thymic carcinoma with central nervous system involvement is very rare in children. A 27-month-old girl presented with a unilateral squint, vomiting, and behavioral changes. Imaging studies showed a silent anterior mediastinal mass and a large metastatic mass at the base of the skull. Biopsy of the anterior mediastinal mass confirmed an undifferentiated tumor consistent with thymic carcinoma. The child died within 3 months of the onset of symptoms, due to progression of the disease. These lethal tumors of unknown histogeneses and etiology are aggressive in nature, resistant to therapy, and have a rapidly fatal course.

[Clinicopathologic analysis of micronodular thymoma with lymphoid stroma].

Objective: To investigate the clinicopathologic features of micronodular thymoma with lymphoid stroma(MNT). Methods: Five cases of MNT diagnosed from January 2007 to December 2016 in Henan Provincial People's Hospital were collected.Hematoxylin-Eosin staining and immunohistochemistry were used to evaluate the histological and immunophenotypic characteristics in 5 MNT cases. Epstein-Barr virus (EBV) status was detected by in situ hybridization for EBV-encoded small RNA (EBER). Polymerase chain reaction was used to detect the rearrangement of immunoglobulin genes. Results: Five cases were MNT, including 3 male and 2 female patients, mean aged 59 years (from 43 to 63 years). All patients had ananterior mediastinal mass, with no myasthenia gravis and autoimmune diseases, and underwent surgical resection.Half to ten years follow-up showed no recurrence.Grossly, the tumors were solid in 4 cases, and cystic and solid in 1 case; the border was clear. Histologically, the tumors presented as a distribution of micronodules separated by abundant lymphoid stroma with prominent germinal centers. The nodules were composed of neoplastic spindle, oval cells containing bland, oval nuclei.Immunohistochemical study showed strong positivity of the tumor cells for CKpan, CK19, CK5/6 and p63. Stains for EMA, CD117, calretinin, TTF1 were negative in the tumor cells.Scattered CD3, CD1a, and TdT positive immature T lymphocytes were noted in and around tumor nodules. Many lymphocytes in the stroma, including germinal centers, were positive for CD20.The bcl-2 was also detected in lymphocytes in the stroma, mantle and marginal zone of lymphoid follicles, and in part of tumor cells. Tumor cells and lymphocytes were negative for EBER. Immunoglobulin genes rearrangement analysis showed that B lymphocytes were polyclonal. Conclusions: MNT is a rare thymoma, which occurs in the elderly and has no obvious symptom. After complete resection, the prognosis is very good. The diagnosis should be based on a combination of clinicopathologic features, and other types of thymoma should be excluded.

Expression of PD-1 and PD-L1 in thymic epithelial neoplasms.

Thymic epithelial neoplasms are rare tumors that are difficult to diagnose and treat. Programmed death 1 (PD-1) receptor and its ligand (PD-L1) are expressed by various malignancies and are considered a prognostic factor and immunotherapeutic target. We examined the expression of both antibodies in 100 thymic epithelial neoplasms to assess their use as a biomarker and to correlate their expression with clinicopathological parameters. Whole-tissue sections of 74 thymomas and 26 thymic carcinomas were examined. Expression of PD-1 and PD-L1 was evaluated by immunohistochemistry and scored by the percentage of positive T-cells or tumor cells, respectively. Cases with strong membranous reactivity of the antibody in ≥5% of T-cells (PD-1) or tumor cells (PD-L1), respectively, were considered positive. Expression of PD-1 was detected in 52/100 cases (52%) including 6/26 thymic carcinomas (23%) and 46/74 thymomas (62%). PD-L1 was positive in 61/100 cases (61%) including 14/26 thymic carcinomas (54%) and 47/74 thymomas (64%). A total of 82 cases (82%) showed expression of PD-1 or PD-L1. PD-1+ cases were associated with higher stage in thymic carcinoma (P=0.01) and PD-1- cases with thymic carcinoma histology (P=0.0014), whereas PD-L1+ cases were associated with neoadjuvant therapy in thymoma (P=0.0065). There was no statistical difference between PD-1 or PD-L1 expression status and other clinicopathological parameters including overall survival. PD-1 and/or PD-L1 are expressed in up to 82% of thymic epithelial neoplasms. These results confirm that these tumors should be considered for PD-1/PD-L1-targeted therapy, however their predictive value in terms of prognosis remains uncertain.

[Efficacy of PD-1/PD-L1 immune checkpoint inhibitors and PD-L1 testing in thoracic cancers]. / Efficacité des inhibiteurs du checkpoint immunitaire PD-1/PD-L1 et testing PD-L1 dans les cancers thoraciques.

Tumoral immune environment is a major component of cancer. Its composition and its organization represent a reproducible characteristic of tumors and a validated prognostic factor. In non-small cell lung cancer (NSCLC), cytotoxic T CD8+ lymphocyte density, associated with a Th1 environment and tertiary lymphoid structures impacts survival. Tumor cell-immune cell interaction is targeted by PD1/PD-L1 inhibitors. In advanced NSCLC, PD1/PD-L1 inhibitors are more effective than second-line chemotherapy. Pembrolizumab outperforms first-line chemotherapy in NSCLC strongly positive for PD-L1. PD1/PD-L1 inhibitors are currently tested in mesothelioma and thymic tumors. PD-L1 expression evaluated with immunochemistry is the most studied predictive biomarker of PD1/PD-L1 inhibitor efficacy. Tumor and immune cell expression of PD-L1 is still difficult to evaluate because of intra-tumoral heterogeneity and expression modulation by the microenvironment. Four commercial diagnostic antibodies are in development, with differences concerning recognized epitopes, methodology of evaluation of PD-L1 expression, positivity threshold, kit and platforms used. Clinical trials in NSCLC have shown that patients with tumors strongly positive for PD-L1 derived the best clinical benefit with PD1/PD-L1 inhibitors whereas clinical benefit is less common in tumors negative for PD-L1. PD-L1 expression is not a perfect biomarker since some PD-L1 negative NSCLC respond to PD1/PD-L1 inhibitors and some PD-L1 positive NSCLC do not. PD-L1 testing is likely to be implemented in daily practice for selection of advanced NSCLC that will be treated with pembrolizumab, underscoring the relevance of ongoing harmonization studies of the use of the different antibodies available for PD-L1 testing.

Microthymoma in elderly-onset myasthenia gravis detected preoperatively.

A 77-year-old woman with a 3-month history of muscle weakness was diagnosed with elderly-onset generalized myasthenia gravis (Myasthenia Gravis Foundation of America classification IIa) based on a high serum acetylcholine receptor antibody level (25.4 nmol·L-1) and neurological findings. Computed tomography detected a small nodule (diameter 15 mm) in the anterior mediastinum, which was suspected to be a thymoma. An extended thymectomy was performed. The pathological examination revealed a 6-mm-diameter thymoma, termed a microthymoma, accompanied with a unilocular thymic cyst without capsule formation (type B2 according to the World Health Organization classification). Some fat tissue was also found within the tumor.

Ectopic thymic carcinoma presenting as an intrathoracic mass.

An asymptomatic 83-year-old man was found to have a right intrathoracic tumor. Computed tomography demonstrated a soft-tissue density mass measuring 55 × 25 × 22 mm adjacent to the right anterior chest wall. At surgery, the tumor was found to adhere to the diaphragm and right lung, contiguous with the mediastinal fat tissue. Histology of the resected specimen demonstrated proliferation of spindle and sarcomatous cells with multinucleated giant cells. Thus the tumor was diagnosed as undifferentiated thymic carcinoma and was considered to have arisen from ectopic thymic tissue. At 2 years postoperatively, the patient had no evidence of recurrence.

Ectopic primary intrathyroidal thymoma: a clinicopathological and immunohistochemical analysis of 3 cases.

Thymomas are rare tumors that occasionally arise from ectopic locations. Ectopic thymomas originating within the thyroid gland are an exceedingly uncommon clinical entity that has only been described sporadically. In this study, we present the clinicopathological and immunohistochemical features of 3 primary intrathyroidal thymomas. The patients were 2 women and 1 man between the ages of 43 and 53 years (average, 48 years). Clinically, the patients presented with neck pain or enlarged thyroid glands. Physical examination and thyroid ultrasound revealed the presence of nodular masses confined to the thyroid parenchyma. No concurrent mediastinal tumors were identified in any of the cases, and none of the patients had a history of thymoma. Fine needle aspirate performed in 1 case was interpreted as possibly Hashimoto thyroiditis. Surgical resection was performed in all cases. Grossly, the lesions were circumscribed masses measuring from 1 to 4 cm in size. Histologically, the lesions showed the classic biphasic cellular proliferation of thymomas characterized by varying proportions of epithelial cells and lymphocytes. Two patients remain alive and well 1.5 to 2 years after their surgical resection, whereas the third patient was lost to follow-up. The cases herein presented highlight an unusual tumor entity that can be clinically confused for more common lesions affecting the thyroid gland. Awareness of this entity is important to avoid misdiagnosis and secure appropriate clinical management.

Ectopic hamartomatous thymoma: report of a case and review of literature.

Ectopic hamartomatous thymoma (EHT) is an exceedingly rare lesion that usually arises in the lower neck and mainly affects adult men. We present the clinicopathological features of a case of EHT in a 28-year-old Chinese male, together with a literature review. Ultrasound imaging and a computed tomography (CT) scan of the neck demonstrated a 3.0-cm well-defined nodule of heterogeneous density located within the left sternocleidomastoid muscle. The patient underwent a gross total resection of the tumor. Grossly, the well-demarcated, encapsulated mass had a predominantly solid and gray-white appearance admixed with microcystic foci filled with serous content and yellowish regions. The lesion consisted of an irregular admixture of spindle cells, epithelium, and mature adipose tissue. Immunohistochemistry showed that both the spindle cell and epithelial components were diffuse and had intense nuclear positivity for p63 and cytoplasmic reactivity for pan-cytokeratin, CK7, and CK19. The patient was followed for 18 months without any evidence of metastasis or recurrence.

Concurrent thymoma, thymic carcinoma, and T lymphoblastic leukemia/lymphoma in an anterior mediastinal mass.

We report a case of a 62-year-old man with concurrent thymoma, thymic carcinoma, and T lymphoblastic leukemia/lymphoma. Computed tomography revealed a 5.5-cm anterior mediastinal mass, and surgical resection was performed. Histologically, the mass showed concurrent thymoma (type AB), thymic carcinoma, and T lymphoblastic leukemia/lymphoma. Lymphoma cells infiltrated in the left lung, pulmonary hilar lymph nodes, and involved bone marrow. The patient underwent chemotherapy for T lymphoblastic leukemia/lymphoma and achieved remission. One year after surgery, he remains free of both thymoma and thymic carcinoma, and T lymphoblastic leukemia/lymphoma remains complete remission under maintenance therapy. Thymoma and T lymphoblastic leukemia/lymphoma can combine in the same mass, although this is quite rare. At the time of the diagnosis of thymoma, additional attention should be directed toward lymphocytes in the background.

Immunohistochemical differentiation between type B3 thymomas and thymic squamous cell carcinomas.

Type B3 thymomas and thymic squamous cell carcinomas have some overlapping histological features, so it is difficult to make the differential diagnosis between these two entities, especially when the biopsy specimen is small. Only a few markers such as CD5 and CD 117 were applied to the differential diagnosis, the purpose of this study is to identify other diagnostic markers to help making the differential diagnosis more accurate. GLUT-1, MUC-1, CD117, CD5, CEA, P63, CK19, CK5/6, CD1a and TdT were evaluated using 16 cases of type B3 thymoma and 20 cases of thymic squamous cell carcinoma. Staining scores were obtained by calculating the percentage of positive cells. The sensitivity of GLUT-1 or MUC-1 for thymic squamous cell carcinomas was highest (100%), followed by CK5/6 (95%), CD117 (90%), P63 (85%), CD5 (80%) and CEA (75%). The specificities of CD5, CD117 and CEA for thymic squamous cell carcinomas all were 100%, next was MUC-1 (56.3%), followed by GLUT-1 (50%), P63 (25%), CK5/6 (12.5%). The sensitivities of CK19, TdT, and CD1a for type B3 thymomas were 100%, 93.8% and 87.5%, respectively. The specificity of CD1a for type B3 thymomas was highest (100%), followed by TdT (95%), CK19 (10%). The reactivity of GLUT-1, MUC-1, CD117, CD5, CEA, CD1a and TdT in thymic squamous cell carcinomas and type B3 thymomas had significant difference. Usually a panel of markers is needed, if we combine GLUT-1 or MUC-1 which sensitivity for thymic squamous cell carcinomas is highest with CD5, CD117, CEA, CD1a or TdT which have high specificity, we can make the differential diagnosis effectively.

A case report of sclerosing thymoma of the anterior mediastinum: an exceedingly rare morphology.

The morphology of thymoma is diverse, although 5 basic subtypes are recognized in the World Health Organization classification system. Sclerosing thymoma was first documented in 1994 and to date only 13 cases have been reported. Sclerosis itself is considered to be an ancient change and can occur in various histological subtypes. Herein, we present a case of a 62-year-old woman incidentally found to have an anterior mediastinal mass, 31 × 24 × 17 mm in size, without an associated autoimmune disease such as myasthenia gravis. The mass was finally diagnosed as sclerosing thymoma derived from type A thymoma. Intraoperative pathological examination using a limited amount of sample did not allow a definitive diagnosis of thymoma in this case. When dealing with fibrous lesions observed in limited samples such as biopsy and intraoperative frozen specimens, recognizing sclerosing thymoma is important since there are several disease entities accompanying fibrosis in the anterior mediastinum.

Metaplastic thymoma with myasthenia gravis presumably caused by an accumulation of intratumoral immature T cells: a case report.

Among human neoplasms, thymomas are well known for their association with paraneoplastic autoimmune diseases such as myasthenia gravis. However, regarding rare metaplastic thymoma, only one case of an association with myasthenia gravis has been reported. Here, we present the second case of a 44-year-old woman with metaplastic thymoma associated with myasthenia gravis. In metaplastic thymoma, intratumoral terminal deoxynucleotidyl transferase-positive T-cells (immature T-cells) are generally scarce, while they were abundant in the present case. We believe that these immature T-cells could be related to the occurrence of myasthenia gravis.

NOTCH1 intracellular domain immunohistochemistry as a diagnostic tool to distinguish T-lymphoblastic lymphoma from thymoma.

Distinction between lymphocyte-rich thymoma and T-lymphoblastic lymphoma/leukemia (T-LBL) can be problematic because of a predominance of precursor T cells in both, particularly if the epithelial component in a thymoma is undersampled. Because of very different clinical implications, accurate diagnosis is critical. The NOTCH1 signaling pathway is frequently activated in T-LBL and plays a central role in the pathogenesis of this disease. Antibodies to NOTCH1 intracellular domain (N1ICD), recognizing the active form of NOTCH1, have been developed. We hypothesized that detection of N1ICD would be useful in distinguishing T-LBL from thymoma and investigated a series of formalin-fixed, paraffin-embedded tissues for immunoreactivity with an N1ICD antibody using automated immunohistochemistry. Slides were scored using a 25% nuclear reactivity threshold for positivity. Hyperplastic tonsil showed positivity in few scattered interfollicular lymphoid cells, suprabasilar epithelial cells, and endothelial cells. Thymocytes from non-neoplastic thymus were largely negative for N1ICD. All thymomas tested (n=23) were negative for N1ICD, although epithelial cells and a small minority of thymocytes may be positive, requiring careful interpretation. All T-LBL cases (n=16) were scored positive for N1ICD: 8 (50%) of these showed diffuse and mostly strong immunoreactivity, whereas the remaining 8 (50%) had less extensive positivity, but with consistently >25% nuclear staining. In conclusion, normal thymocytes do not express significant levels of N1ICD. In keeping with this pattern, thymomas are negative for N1ICD, whereas a high percentage of T-LBL expresses N1ICD. Thus, N1ICD immunohistochemistry appears to be a useful method in distinguishing T-LBL from thymoma.

Adenocarcinoma of the thymus, enteric type: report of 2 cases, and proposal for a novel subtype of thymic carcinoma.

We report 2 cases of primary thymic adenocarcinoma with enteric differentiation. One carcinoma occurred in a 41-year-old man as a 7-cm-diameter cystic tumor and the other one in a 39-year-old woman as a 6-cm-diameter solid mass. Both tumors were located in the anterior mediastinum. Clinical staging did not reveal any extrathymic tumor. Histologically, the tumors were classified as adenocarcinoma, not otherwise specified, and a mucinous (colloid) carcinoma, respectively. Immunohistochemically, both tumors were positive for cytokeratin 20 (CK20), CDX2, and carcinoembryonic antigen, reflecting enteric differentiation. A review of the literature on 43 other cases of primary thymic adenocarcinomas suggested 11 further cases with enteric differentiation, as assessed by CK20 and/or CDX2 expression. We propose that thymic adenocarcinoma with enteric differentiation represents a novel subtype of thymic carcinoma. It is mostly of mucinous morphology and frequently associated with thymic cysts. The clinical outcome is variable. Recognition of primary thymic adenocarcinoma with enteric differentiation is helpful for the differentiation from metastatic disease, mainly from the gastrointestinal tract.

Diagnostic significance of cell kinetic parameters in World Health Organization type A and B3 thymomas and thymic carcinomas.

The prognostic importance of histologic classifications of thymic epithelial neoplasms is controversial. Evidence suggests that difficulties in reproducibility affect prognostic studies. Two thoracic pathologists independently classified 80 cases of type A or B3 thymoma and thymic carcinoma according to World Health Organization (WHO) classification. Ki-67 labeling index (LI) was used to identify cutoff points between WHO types. Recursive partitioning (Rpart) and ad hoc methods separated the data points. The pathologists agreed on type A (n = 31), type B3 (n = 21), and thymic carcinoma (n = 14). Ki-67 LI differed between types A and B3 (P < .001) and between thymic carcinoma and type A (P < .001) or type B3 (P = .001). Mitotic activity differed between thymic carcinoma and type A (P < .001) or type B3 (P < .001). Rpart revealed Ki-67 LI greater than 14.0% only in thymic carcinoma; cases with Ki-67 LI less than 5.1% did not represent thymic carcinoma. Ad hoc analysis showed Ki-67 LI greater than or equal to 13.5% represents thymic carcinoma; only type A had Ki-67 LI less than 2%. The pathologists disagreed on histologic type in 14 cases. In 11 of 14 cases with available Ki-67, the Rpart method predicted the WHO type; in 7 of 14 cases, the ad hoc method predicted the WHO type. In conclusion, Ki-67 LI is helpful in differentiating thymic epithelial neoplasms, with Ki-67 LI less than 2% and greater than or equal to 13.5% distinguishing type A thymoma and thymic carcinoma, respectively.