Cutaneous metastasis of SMARCA4‐deficient thoracic sarcoma: A diagnostic dilemma with therapeutic implications

SMARCA4-deficient thoracic sarcoma (SMARCA4-DTS) is a recently recognized entity with undifferentiated rhabdoid morphology and mutations in the switch/sucrose nonfermenting BRG1-associated factors complex. Patients are typically males in their fifth decade with a history of smoking who present with rapidly progressive intrathoracic disease and follow an aggressive clinical course. Metastatic disease is reported in up to 77% of cases; however, to our knowledge, cutaneous metastasis has not been reported nor has it been reported as the initial manifestation of the disease. Recognizing SMARCA4-DTS from other types of epithelioid tumors that involve the skin is clinically relevant, as targeted therapies for SMARC-deficient tumors are currently being investigated and early clinical trial data show therapeutic benefit.