Rectal metastasis from primary small-cell lung cancer: A case report and literature review.

RATIONALE: Small-cell lung cancer (SCLC) is a subtype of primary lung cancer that has a very poor overall survival rate because of its propensity for metastasis and incredibly high proliferation rate. For most patients with lung cancer, metastatic disease is discovered at the time of initial diagnosis. About 70% of individuals with SCLC already have metastases in their brain, liver, lymph nodes, and bones at the time of diagnosis. Rectal metastases are uncommon.

PATIENT CONCERNS: In this case report, we described a 73-year-old female patient who was diagnosed with neuroendocrine SCLC based on a lung biopsy obtained by needle. The patient had blood in the stool, accompanied by loss of appetite and pain around the umbilicus for 6 months. The symptoms gradually worsened.

DIAGNOSES: Rectal pathological results revealed that metastatic poorly differentiated neuroendocrine carcinoma originated from the lung.

INTERVENTIONS: The patient underwent 4 courses of chemotherapy.

OUTCOMES: The hematochezia then subsided, and radiological evaluation of the rectal metastases and primary lung tumors suggested a partial response.

LESSONS: When a rectal tumor is identified, it is important to differentiate metastatic diseases and make a definitive diagnosis through detailed immunohistochemical evaluation and systemic imaging surveillance.