Pulmonary Pleomorphic Carcinoma Mimicking Small Bowel Obstruction.

Pulmonary pleomorphic carcinoma (PC) is a rare and aggressive subtype of sarcomatoid carcinoma. It is characterized by poorly differentiated cells with both epithelial and mesenchymal features and often presents as a peripheral lung mass. Metastasis to the gastrointestinal tract is exceedingly rare. We report the unusual case of an 87-year-old man with a prior history of lung adenocarcinoma who presented with abdominal pain secondary to a small bowel obstruction. Imaging revealed a right lower quadrant mass, and surgical exploration uncovered an undifferentiated malignant tumor involving the small bowel mesentery. Histopathological analysis demonstrated spindle cells, giant cells, and rhabdoid features with positive immunostaining for thyroid transcription factor-1 (TTF-1), Napsin A, and CK7, consistent with metastatic PC. Additional imaging revealed widespread disease including masses in the gastrohepatic region, adrenal gland, and sacrum. This case highlights a rare manifestation of pulmonary PC with metastasis to the small bowel causing obstruction, an uncommon but important differential diagnosis in lung cancer patients presenting with abdominal symptoms. Early recognition is critical, as atypical metastatic patterns may delay diagnosis and impact clinical management.