A Rare Case of Metastatic Carcinosarcoma Presenting as a Simple Upper Lip Mass

Background: Carcinosarcoma is a rare, aggressive malignancy exhibiting both epithelial and mesenchymal components. It typically arises in the uterus, lung, or gastrointestinal tract, and oral cavity involvement is extremely uncommon. Here, we report a rare case where a metastatic carcinosarcoma initially presented as a benign-appearing upper lip lesion. Case presentation: A 47-year-old male presented with a painless upper lip mass persisting for two months. The lesion appeared benign but was excised and revealed malignant features on frozen section. Systemic imaging identified multiple hypermetabolic lesions in the lung, colon, liver, pancreas, adrenal glands, and lymph nodes. Histopathology of the lip, colon, and lung lesions showed a high-grade biphasic tumor. Immunohistochemistry confirmed co-expression of cytokeratin and vimentin, consistent with carcinosarcomatous differentiation and epithelial-mesenchymal transition. No primary tumor was identified, and the case was diagnosed as metastatic carcinosarcoma of unknown origin. The patient began palliative chemotherapy. Conclusions: This case emphasizes the importance of early biopsy and thorough systemic evaluation of persistent oral lesions. Carcinosarcoma, though rare, should be considered in the differential diagnosis of aggressive tumors in atypical locations.