Sarcomatoid carcinoma of the lung presenting as a cutaneous metastasis

The author reports a very rare case of cutaneous metastasis of sarcomatoid carcinoma of the lung. The skin metastasis was an initial presentation. A 67‐year‐old man consulted our hospital because of left chest skin mass. An excisional biopsy was performed, and it showed proliferation of malignant sarcomatoid spindle and polygonal cells in the deep dermis and subcutis remote from the epidermis and appendages. Immunohistochemically, the tumor cells were positive for pancytokeratins, cytokeratin (CK) 7, CK 18, vimentin, p53, Ki‐67 (95%) and PDGFRA. They were negative for high molecular weight CK, CK 5/6, CK 14, CK 19, CK 20, epithelial membrane antigen, TTF‐1, CEA, desmin, S100 protein, α‐smooth muscle actin, p63, CD34, surfactant apoprotein A, chromogranin, synaptophysin, neuron‐specific enolase, CD68, CD56, D2‐40, calretinin and KIT. A pathological diagnosis of metastatic sarcomatoid carcinoma probably originating from the lung was made. Then, the patient was admitted to our hospital, and imaging modalities including compured tomography (CT) and magnetic resonance imaging (MRI) revealed a tumor in the left lung. No other tumors were detected in the imaging techniques. Lung biopsy was planned, but the patient suddenly died; the cause of death was unclear. Autopsy was not performed. The present report suggests that sarcomatoid carcinoma of the lung should be considered in cutaneous metastatic lesions. Terada T. Sarcomatoid carcinoma of the lung presenting as a cutaneous metastasis.