Diffuse malignant biphasic peritoneal mesothelioma with cystic areas

Area of Science:

• Oncology
• Pathology

Background:

• Malignant mesothelioma is a rare cancer, often associated with asbestos exposure.
• Peritoneal mesothelioma involves the lining of the abdomen, presenting unique diagnostic challenges.
• Cystic features within mesothelioma can complicate histopathological diagnosis.

Observation:

• A case of peritoneal biphasic mesothelioma with prominent cystic areas is presented in a patient with occupational asbestos exposure.
• Histological examination revealed focal epithelial proliferations and spindle cell proliferation surrounding cystic spaces.
• Immunohistochemical markers (EMA, vimentin, CK5/6, D2-40, calretinin, P53) were positive, while desmin was negative.

Findings:

• The immunohistochemical profile supported the diagnosis of biphasic mesothelioma, aiding in differential diagnosis from benign cystic mesothelioma.
• The presence of atypia and mitoses was minimal, underscoring the diagnostic difficulty posed by cystic areas.
• Confirmation of the biphasic histotype required extensive tumor sampling, despite seemingly favorable histological and clinical prognostic indicators.

Implications:

• This case highlights the importance of thorough histopathological evaluation and immunohistochemistry in diagnosing rare variants of malignant mesothelioma.
• Recognizing cystic features in peritoneal mesothelioma is critical for accurate diagnosis and appropriate patient management.
• The findings emphasize that biphasic mesothelioma, even with mild features, represents an aggressive histotype requiring careful consideration.