Spindle cell carcinoma with cystic brain metastasis: Successful treatment with stereotactic radiotherapy and anti‑programmed cell death‑1 antibodies: A case report.

Cystic brain metastasis is a rare condition that mainly originates from lung or breast adenocarcinomas. By contrast, pulmonary spindle cell carcinoma, a rare type of non-small cell carcinoma, has not been reported with this condition. Cystic brain metastases are characterized by larger tumor sizes with increased peritumoral edema compared with solid metastases. Therefore, specific treatment strategies are required for intracranial disease control. Immunotherapy has recently been demonstrated to be crucial for treating pulmonary sarcomatoid carcinomas based on high programmed cell death-ligand 1 (PD-L1) expression observed in these cancers. The present report describes the case of an 82-year-old man diagnosed with pulmonary spindle cell carcinoma, a rare subtype of sarcomatoid carcinoma. At 7 months after the diagnosis, the patient complained of a walking disturbance for which brain metastasis with peritumoral edema was the causative agent. The brain tumor had a large cystic component, and thus, an Ommaya reservoir catheter was implanted for cyst aspiration but collapsed early without sufficient volume reduction. The patient was transferred to receive twice-split gamma knife treatment, which shrank the solid compartment and reduced the cyst volume, thereby relieving neurological defects. The patient was subsequently treated with immunotherapy targeting programmed cell death-1 based on the high PD-L1 expression in the lung tumor specimen. The thoracic tumors regressed following immunotherapy and progression-free survival was maintained for 16 months. To the best of our knowledge, the present report provides the first description of focal and systemic therapies for pulmonary spindle cell carcinoma with cystic brain metastasis. The report also discusses the treatment strategies for cystic brain metastases and reviews cases of pulmonary spindle cell carcinoma treated with immune checkpoint inhibitors.