Case Report: Prostate metastasis from pulmonary sarcomatoid carcinoma: the first reported case and clinical implications of palliative radiotherapy.

Pulmonary sarcomatoid carcinoma (PSC) is a highly aggressive lung cancer subtype. Prostate metastasis is extremely rare in lung cancer, and no PSC case with immunohistochemical confirmation has been reported. We report a 68-year-old man diagnosed with left upper lobe carcinosarcoma (myogenic differentiation) on pathological biopsy. He underwent multimodal treatment, including radical resection, adjuvant chemotherapy, anlotinib targeted therapy, and local thoracic radiotherapy. Eight months later, he developed progressive dysuria. Whole-body positron emission tomography-computed tomography (PET-CT) showed hypermetabolic lesions in the prostate and multiple systemic sites, while the serum prostate-specific antigen (PSA) level remained normal. Transurethral resection of the prostate (TURP) was performed, and pathology confirmed metastatic sarcomatoid carcinoma. Palliative radiotherapy to the prostate (62.5 Gy/25 fractions) completely resolved his urinary symptoms. The patient died 11 months after diagnosis from pulmonary infection. This is the first documented case of prostate metastasis from PSC worldwide. For such patients, histopathological and immunohistochemical confirmation is indispensable, and palliative radiotherapy can effectively relieve urinary symptoms.