Distant cutaneous metastasis of malignant epithelioid mesothelioma.

Malignant mesothelioma is a locally aggressive malignancy most commonly arising from the pleural and/or peritoneal cavity. Distant cutaneous metastasis is extremely rare. Here, we describe two cases of mesothelioma metastatic to the head and neck skin. Case 1: A 64-year-old man diagnosed previously with extensive thoracic and abdominal mesothelioma, developed a rapidly growing right upper lip lesion, for which a wedge resection was performed. Case 2: A 77-year-old woman with a history of pleural mesothelioma developed a firm, mobile subcutaneous nodule on the right lateral forehead, clinically thought to represent either an epidermal inclusion cyst or a lipoma. A punch biopsy was performed. In both cases, histopathologic evaluation revealed dermal proliferation of epithelioid cells with moderate cytologic atypia and three mitotic figures per mm2 and two mitotic figures per mm2 for Cases 1 and 2, respectively. Immunohistochemical studies revealed the lesional cells to be positive for WT1, mesothelin, D2-40, CK5/6, while being negative for melanocytic and other keratinocytic markers, supporting a diagnosis of metastatic mesothelioma. Awareness of rare instances of cutaneous metastases from malignant mesothelioma is necessary to avoid possible misdiagnosis and ensure appropriate management.