A Rare Case of Lung Squamous Cell Carcinoma Metastasizing to an Anterior Abdominal Wall Schwannoma.

Metastasis to benign tumors is an uncommon phenomenon, with schwannomas being rare recipients of metastatic disease. We report a rare case of a 60-year-old female with lung squamous cell carcinoma (SCC) developing metastasis to an anterior abdominal wall schwannoma. The patient was diagnosed with lung SCC and received three cycles of neoadjuvant chemoimmunotherapy. Follow-up Positron Emission Tomography/Computed Tomography (PET-CT) revealed a metabolically active primary lung lesion with metastatic lymphadenopathy and subcutaneous fat stranding in the left hypochondrial and lumbar region. She underwent thoracoscopy with pleural biopsies and excision of the anterior abdominal wall lesion. Histopathology confirmed metastatic SCC in the pleural deposits and a schwannoma in the anterior abdominal wall, harboring metastatic SCC foci confirmed by p40 immunohistochemistry (IHC). This case highlights the diagnostic challenges posed by metastasis to benign tumors and underscores the importance of thorough pathological evaluation.