Colonic Metastasis of Primary Lung Cancer

Abstract

The colon is an uncommon secondary site for metastasis of lung adenocarcinoma. Distinguishing primary colonic carcinoma from metastatic spread of lung carcinoma can be difficult. We present a case of a patient with lung adenocarcinoma who, on abdominal computed tomography scan examination, was found to have a sigmoid tumor that was thought to represent a synchronous primary colorectal adenocarcinoma. Histological examination of endoscopic sigmoid tumor biopsies confirmed this to be metastasis from the lung adenocarcinoma. The patient subsequently developed major rectal bleeding and deteriorated significantly. This case also illustrates the poor prognosis association with colorectal metastasis of lung cancer.

Keywords: Adenocarcinoma; Lung cancer; Metastasis; Squamous cell carcinoma.

Fig. 1

Axial CT thorax (a) with contrast showing a lobulated 7.3 cm soft tissue right paratracheal mass extending from the origin of the SVC to the superior aspect of the right atrium. The tumor invades the posterior wall of the superior vena cava and proximal right main pulmonary artery anterior/apical branches. Enlarged subcarinal lymph nodes are also seen. Axial CT Abdomen (b) showing circumferential thickening in the region of the descending/sigmoid colon was likely colonic primary tumor. CT, computed tomography; SVC, superior vena cava.

Fig. 2

Colonoscopy showing (a) a circumferential necrotic sigmoid mass. Microscopic views (b) of embedded parts. There is a poorly differentiated tumor diffusely infiltrating the lamina propria in-between nondysplastic colonic crypts. High power view (c) showing poorly differentiated adenocarcinoma with occasional signet ring cells (arrows).

Fig. 3

On IHC staining, the tumor cells show strong diffuse nuclear positivity with TTF1 (a) and are also focally positive for cytokeratin 7 (b). c The tumor is negative for CDX2, while the background colonic crypts show normal strong nuclear expression. IHC, immunohistochemical staining.