The epithelioid MPM can grow with 4 different patterns: tubular, papillary (the most common, often found in association with other patterns), diffuse, and deciduoid (cells with abundant glassy eosinophilic cytoplasm). Atypia is a frequent feature but is typically mild; only a few cases have moderate or severe atypia.[16] Unusual histologic features include lymphoid follicles, striking myxoid stroma, prominent foamy histiocytes, and marked vascular proliferation. Multicystic mesotheliomas and well-differentiated papillary mesothelioma are histological types associated with a long survival in the absence of treatment.[8]
Sarcomatoid mesothelioma is extremely rare: Neumann and colleagues[33] in a series of 53, and Deraco and colleagues[34] in a series of 49 MPM reported no sarcomatoid histotypes. It is composed of a fascicular proliferation of spindle cells with oval nuclei, scant amphophilic cytoplasm and occasionally prominent nucleoli. In general, sarcomatoid mesotheliomas show more atypia than their epithelioid counterparts, and often display mitotic activity and foci of necrosis. The tumor cells can display a fibrosarcoma-like appearance; therefore, sarcomatoid MPM must be differentiated from the rare variant of extra-intestinal gastrointestinal stromal tumors (GISTs) with sarcomatoid features or from true retroperitoneal sarcomas.
A large number of immunohistochemical markers have been suggested for diagnostic aid, but none of the markers alone is diagnostic. However, they become very useful when used as a panel. Malignant MPM is characterized by positive staining for EMA, calretinin, WT1, cytokeratin 5/6, antimesothelial cell antibody-1, and mesothelin. Cytokeratins help to confirm invasion and to distinguish mesothelioma from sarcoma and melanoma.
Sarcomatoid mesothelioma is extremely rare: Neumann and colleagues[33] in a series of 53, and Deraco and colleagues[34] in a series of 49 MPM reported no sarcomatoid histotypes. It is composed of a fascicular proliferation of spindle cells with oval nuclei, scant amphophilic cytoplasm and occasionally prominent nucleoli. In general, sarcomatoid mesotheliomas show more atypia than their epithelioid counterparts, and often display mitotic activity and foci of necrosis. The tumor cells can display a fibrosarcoma-like appearance; therefore, sarcomatoid MPM must be differentiated from the rare variant of extra-intestinal gastrointestinal stromal tumors (GISTs) with sarcomatoid features or from true retroperitoneal sarcomas.
A large number of immunohistochemical markers have been suggested for diagnostic aid, but none of the markers alone is diagnostic. However, they become very useful when used as a panel. Malignant MPM is characterized by positive staining for EMA, calretinin, WT1, cytokeratin 5/6, antimesothelial cell antibody-1, and mesothelin. Cytokeratins help to confirm invasion and to distinguish mesothelioma from sarcoma and melanoma.
No comments:
Post a Comment