Pulmonary spindle cell carcinoma with unusual morphology: A rare case report and review of the literature.

Rationale: Pulmonary spindle cell carcinoma (PSCC) is a highly malignant carcinoma that often exhibits the histopathological characteristic of cell pleomorphism.

Patient Concerns: Here, we report a PSCC case in a 59-year-old woman with multiple metastases. The pathological manifestation of this case did not show high-grade pleomorphism or atypia, and was easily mimicked by other borderline or low-grade malignant tumors such as an inflammatory myofibroblastic tumor (IMT).

Diagnoses: Based on the results of immunohistochemistry and fluorescence in situ hybridization after the operation, IMT was ruled out, and PSCC was confirmed.

Interventions: Resection of the right middle lobe and dissection of the lymph nodes were performed. The patient was given 2 cycles of chemotherapy with cisplatin and 1 cycle of radiotherapy after the operation.

Outcomes: Metastatic lesions in the left kidney, the right lung, the first thoracic vertebrae, the retroperitoneal lymph nodes, and the mediastinal lymph nodes were identified by positron emission tomography/computed tomography 4 months after the operation, and the patient died 2 months later.

Lessons: PSCC is a highly malignant carcinoma, but it rarely shows a low-grade malignant histological morphology. So, efforts should be focused on differentiating it from other borderline or low malignant tumors (such as IMT) to avoid misdiagnosis.