Thymic Mucoepidermoid Carcinoma: A Systematic Review and Meta-analysis Thymic mucoepidermoid carcinoma is a rare tumor that remains poorly characterized and a diagnostic challenge. The aim of this review is to characterize this tumor in a larger cohort of patients using all the available cases in the literature. We systematically searched the PubMed and Scopus database for primary thymic mucoepidermoid carcinoma. A total of 24 studies were included in the final analysis. A total of 41 patients were identified; 23 (56.1%) were male and 18 (43.9%) were female. Mean age was 49.8±21.3 years. Mean tumor size was 7.6±3.5 cm. Twenty (66.7%) were low grade and 8 (26.7%) were high grade. In total, 20 (55.6%) patients were treated with surgery alone. Nodal dissection was performed in 4 cases only. Two patients had MAML2 gene rearrangement and 2 were negative. Follow-up time varied from 2 to 93 months. A total of 13 (44.8%) patients died of disease with a median survival of 12 months. There seems to be a bimodal age distribution with peaks between second and third decades of life, and between sixth and eight decades. Lymph node sampling is frequently not performed; however, we recommend performing it, as it may lead to more accurate staging. There is limited data regarding the utility of MAML2 gene rearrangement in the thymic location. Histologic grade and tumor stage/resectability are the main prognostic factors.

Primary Mediastinal Nodal and Extranodal Non-Hodgkin Lymphomas: Current Concepts, Historical Evolution, and Useful Diagnostic Approach: Part 1 Primary mediastinal non-Hodgkin lymphomas (PM-NHLs) represent ~5% of all NHLs and comprise lymphomas of B-cell and T-cell origin. PM-NHLs are defined as involvement of mediastinal lymph nodes, thymus, and/or mediastinal organs (heart, lung, pleura, pericardium) by NHL without evidence of systemic disease at presentation. The clinical scenario is variable and depends on the lymphoma subtype. The radiologic presentation is also variable ranging from a mediastinal mass with or without superior vena cava syndrome, a pleural or a cardiac mass associated with an effusion, or as an effusion only. The diagnosis of PM-NHLs can only be established by microscopic evaluation, and therefore, general pathologists should be aware of these tumors and familiar with their diagnostic approach. The most common anterior mediastinal NHLs (90% to 95%) are primary mediastinal large B-cell lymphoma and T lymphoblastic lymphoma. Thymic marginal zone lymphoma and mediastinal gray zone lymphoma are very rare. The remainder PM-NHLs involving middle or posterior mediastinum include diffuse large B-cell lymphoma (DLBCL) and rare cases of T-cell lymphoma, including anaplastic large cell lymphoma and breast implant-associated anaplastic large cell lymphoma extending to the anterior mediastinum. Primary pleural and cardiac NHLs are mostly DLBCLs. Other rare subtypes of PM-NHLs include DLBCL associated with chronic inflammation/pyothorax-associated lymphoma, fibrin-associated DLBCL (both EBV+), and pleural and/or pericardial primary effusion lymphoma (HHV-8+/EBV+). We review the historical aspects, epidemiology, clinico-radiologic features, histopathology, immunohistochemistry, differential diagnosis, and relevant cytogenetic and molecular features of PM (thymic) LBCL, PM “nonthymic” DLBCL, BCL, unclassifiable, with features intermediate between DLBCL and classic Hodgkin lymphoma (mediastinal gray zone lymphoma), DLBCL associated with chronic inflammation (pyothorax-associated lymphoma), fibrin-associated DLBCL, and primary effusion lymphoma. This review represents the first part of 2 manuscripts covering PM-NHLs.

Primary Mediastinal Nodal and Extranodal Non-Hodgkin Lymphomas: Current Concepts, Historical Evolution, and Useful Diagnostic Approach: Part 2 Primary mediastinal non-Hodgkin lymphomas (PM-NHLs) represent ∼5% of all non-Hodgkin lymphomas (NHLs) and comprise lymphomas of B-cell and T-cell origin. PM-NHLs are defined as involvement of mediastinal lymph nodes, thymus, and/or mediastinal organs (heart, lung, pleura, pericardium) by NHL without evidence of systemic disease at presentation. The clinical scenario is variable and depends on the lymphoma subtype. The radiologic presentation is also variable ranging from a mediastinal mass with or without superior vena cava syndrome, a pleural or a cardiac mass associated with effusion, or as an effusion only. The diagnosis of PM-NHLs can only be established by microscopic evaluation, and therefore, general pathologists should be aware of these tumors and familiar with their diagnostic approach. The most common anterior mediastinal NHLs (90% to 95%) are primary mediastinal (PM) large B-cell lymphoma and T-lymphoblastic lymphoma. Thymic marginal zone lymphoma and mediastinal gray zone lymphoma are very rare. The remainder PM-NHLs involving middle or posterior mediastinum include diffuse large B-cell lymphoma (DLBCL) and rare cases of T-cell lymphoma, including anaplastic large cell lymphoma and breast implant-associated anaplastic large cell lymphoma extending to the anterior mediastinum. Primary pleural and cardiac NHLs are mostly DLBCLs. Other rare subtypes of PM-NHLs include DLBCL associated with chronic inflammation/pyothorax-associated lymphoma, fibrin-associated DLBCL (both Epstein-Barr virus positive), and pleural and/or pericardial primary effusion lymphoma (human herpesvirus-8 positive/Epstein-Barr virus positive). We review the historical aspects, epidemiology, clinicoradiologic features, histopathology, immunohistochemistry, differential diagnosis, and relevant cytogenetic and molecular features of the remaining mediastinal B-cell lymphomas, including primary thymic marginal zone lymphoma of the mucosa-associated lymphoid tissue type, other PM small B-cell lymphomas, PM plasmacytoma, and the most relevant PM T-cell lymphomas.

Immunohistochemistry as a Genetic Surrogate in Dermatopathology: Pearls and Pitfalls Immunohistochemistry (IHC) is routinely performed in most laboratories, and other than purchase of commercially available antibodies, requires no additional equipment or reagents. As such, IHC is an accessible and relatively inexpensive test and one that can be performed quite quickly. This is in sharp contrast to genomic or mutational testing methodologies that are routinely “send out” tests as they require specialized equipment and reagents as well as individuals with expertise in the performance of the tests and analysis of the results, resulting in a prolonged turn-round-time and enhanced associated costs. However, many open questions remain in a rapidly changing therapeutic and scientific landscape with most obvious one being what exactly is the utility of “good old fashioned” IHC in the age of targeted therapy? For molecular applications, is a negative immunohistochemical result enough as a stand-alone diagnostic or predictive product? Is a positive immunohistochemical result perhaps more suitable for a role in screening for molecular alterations rather than a definitive testing modality? This review is an attempt to answer those very questions. We elucidate the broad range of entities in which IHC is currently used as a molecular surrogate and underscore pearls and pitfalls associated with each. Special attention is given to entities for which targeted therapies are currently available and to entities in which molecular data is of clinical utility as a prognosticator.

Classification of Endometrial Carcinoma: New Perspectives Beyond Morphology Endometrial carcinoma has been traditionally divided into type 1 or endometrioid type that is usually moderate to well differentiated and type 2 that is usually poorly differentiated with high histologic grade and aggressive clinical behavior. However, interobserver diagnostic agreement is suboptimal, particularly among the high-grade histotypes. Furthermore, recent data indicate that this histotype assignment does not independently correlate with survival. In recent years, there has been remarkable progress in our understanding of the molecular basis of endometrial carcinoma and extensive molecular studies have been performed under The Cancer Genome Atlas Program (TCGA) leading to molecular classification of endometrial carcinoma that has been shown to be significantly prognostic. This classification system divides the tumors into 4 subgroups namely, polymerase ε exonuclease (POLE) ultramutated, hypermutated microsatellite instability, copy number low, and copy number high (serous-like). Carcinomas with POLE domain hotspot mutations are highly prognostically favorable; those with copy number alterations and TP53 mutations are highly aggressive; and microsatellite unstable and “copy number low” endometrioid are associated with intermediate prognoses. The TCGA applied methods that are too costly and cumbersome for widespread implementation into routine clinical practice. Several other groups have attempted to identify these categories by using immunohistochemical biomarkers rather than molecular studies. Immunohistochemical biomarkers have been used successfully to identify all the subgroups except for POLE ultramutated, which requires sequencing for proper categorization. It is hoped that future studies will identify a suitable biomarker for POLE mutation so that this classification can be routinely used in all medical centers.