The unexpected colonic biopsy: metastasis pulmonary carcinoma to the colon

Abstract

Case report A 72-year-old lady underwent an elective colonoscopy and had a 22 mm sigmoid colon polyp removed. Histologically the polyp showed a tubulovillous adenoma with low grade dysplasia. Within the lamina propria, there was a metastatic carcinoma comprising of solid sheets and nests of large eosinophilic cells with vesicular nuclei and conspicuous nucleoli. No gland formation or intracytoplasmic vacuole was seen. The tumour cells were TTF-1 and CK7 positive. There was no tumour positivity for SlOO, HMB45, ER, PR, CD20, CD3, AEl/3, Cam5.2, CK20, CD56, chromogranin, synaptophysin, CD68, desmin, CD34 and PLAP. On further history, she had a recent lung biopsy for a cystic lung lesion. The lung core biopsies were reviewed and showed sheets of malignant epithelial cells with vesicular nuclei and abundant eosinophilic cytoplasm. There was no keratin or evidence of intercellular bridge. The tumour cells stained for TTF-1 and CK7 and there was no tumour staining for CK5/6 and CK20. The cytomorphology and immunophenotype of both lung and colon biopsies were similar and a diagnosis of metastatic pulmonary carcinoma to the colon was made. Discussion Lung cancer is the most frequent cause of cancer death and approximately 50% of the patients present with distant metastasis at the time of initial diagnosis. The common metastatic sites include the brain, liver, adrenal glands, and bone. Several autopsy studies reported that gastrointestinal metastases from primary lung cancer occur in about 0.2-11.9% of cases. Within the gastrointestinal tract, the small bowel is the most common site of metastases from primary lung cancer. However colonic metastasis is considered extremely rare. This report presents a rare clinical case of metastasis pulmonary carcinoma to the colon.