Metastasis of malignant peritoneal epithelioid mesothelioma in endoscopic gastric biopsy: a diagnostic pitfall.

Aim: To describe a case of metastasis of malignant peritoneal epithelioid mesothelioma in gastric antral mucosa in a patient with a cryptogenic liver cirrhosis associated with esophageal varices, abdominal pain and distension, ascites, and weight loss. Materials and method: The patient underwent esophageal gastric endoscopy for varices, and a biopsy of a polypoid antral lesion was performed. The latter revealed a proliferation of polygonal cells with moderately atypical nuclei and pale eosinophilic, peripherally condensed cytoplasm infiltrating into the lamina propria between the normal mucosal glands of the antrum. The tumor cells were diffusely positive to anticalretinin antibody, whereas anti-claudin 4 and anti-CEA antisera were negative. Conclusions: Metastases of malignant peritoneal mesotheliomas are unusual, and a predominantly gastrointestinal localization is rare. Pathologists should be aware of this possibility to avoid misdiagnosis, particularly in small biopsy specimens.