Carcinosarcoma ex Pleomorphic Adenoma of the Submandibular Gland in a 64-Year-Old Man: A Case Report

Carcinosarcoma (CS) is a rare tumor, consisting of both carcinomatous and sarcomatous components. In this paper, we present a case of CS arising from a pleomorphic adenoma (PA) of the submandibular gland. A 64-year-old Japanese man presented with a left submandibular mass that had developed for 20 years with complaints of pain for the last 3 months. Magnetic resonance imaging showed a lesion involving the left submandibular gland. The patient underwent total dissection of the left submandibular gland and left cervical lymph nodes. Upon gross examination, the mass appeared completely covered by fibroadipose tissue measuring 46×42×45 mm; sectioning revealed a solid-white nodule with central bleeding and necrosis, invading into the surrounding adipose tissue. Microscopically, the presence of carcinomatous and sarcomatous components in the fibro-myxomatous stroma was detected, suggestive of pre-existing PA. The carcinoma component was diagnostic of salivary adenocarcinoma, not otherwise specified, whereas the sarcomatous component exhibited features of osteosarcoma characterized by formation of osteoid. As the border between the carcinomatous and sarcomatous components was not evident, CS may have occurred via transformation of the carcinoma into sarcoma. Tumor metastasis was detected in the cervical lymph nodes. Immunohistochemically, AE1/AE3 expression was noted in the carcinomatous component, but not in the osteosarcoma component. Both components were diffusely positive for vimentin. Four months after the operation, the patient developed a metastatic CS lesion in the lung, suggesting tumor aggression.