Diagnosis of Small Cell Lung Cancer During Screening Colonoscopy

Abstract

INTRODUCTION: Small cell lung cancer (SCLC) is an aggressive malignancy associated with cigarette smoking. Patients commonly present with metastatic disease, though gastrointestinal metastasis is rare. We present a case of SCLC with metastasis to the colon, detected during colorectal cancer screening. CASE PRESENTATION: A 59 year old male with a 60 pack year smoking history plus diabetes and alcoholic cirrhosis, presented for screening colonoscopy. The patient reported a 10 pound weight loss over 2 months, but was otherwise aymptomatic. Colonoscopy revealed multiple polyps throughout the colon. Immunostaining of the biopsied lesions revealed neoplastic cells positive for TTF-1, CK-7, three neuroendocrine markers (NSE, chromogranin A and synaptophysin) and negative for CK 20, indicative of metastatic small cell lung cancer. CT scan of the chest revealed a large central lesion involving the right upper lobe with unilateral hilar lymphadenopathy. A body CT scan performed one year earlier did not show lesions in the Chest. Bronchoscopy revealed an endobronchial mass in the right mainstem bronchus, with biopsy indicating SCLC. MRI and PET scans were consistent with brain and liver metastases. The patient was treated with brain radiation and Etoposide and Carboplatin, with repeat CT scan showing some decrease in size of liver masses. DISCUSSION: Small cell lung cancer is known to be rapidly growing and highly metastatic. The majority of patients with SCLC present with respiratory or constitutional symptoms, or clinical evidence of metastatic disease involving the liver, adrenals, bone, bone marrow, and/or brain. Occasionally, patients present with a paraneoplastic syndrome. Metastasis to the colon is a rare finding. The positive thyroid transcription factor-1(TTF-1) allowed differentiation from a primary gastrointestinal small cell cancer, in which lung involvement has not been described and TTF-1 is negative. Diagnosis of metastatic SCLC during a screening colonoscopy in a patient without gastrointestinal symptoms has not been previously reported. CONCLUSIONS: Metastasis of small cell lung cancer is typical, though spread to the colon is rare. Based on tumor markers and imaging studies, our patient had primary SCLC with colonic metastasis. This case demonstrates how SCLC can present in atypical ways, and also underlines the importance of age appropriate cancer screening.