Synchronous Colonic Adenocarcinoma and Metastatic Lobular Carcinoma in a Colectomy Specimen: A Rare Finding

Abstract

Invasive lobular carcinoma is the second-most-common subtype of invasive breast carcinoma. Its metastatic pattern is different compared to invasive carcinoma-no special type. It metastasizes more often to the gastrointestinal tract, peritoneum, pleura, and ovaries. The extrahepatic gastrointestinal tract metastases occur mostly in the stomach and small intestine and less often in the colon and rectum. We present a case description of an 87-year-old woman admitted to our hospital with hematochezia, abdominal discomfort, fatigue, and weight loss. A colonoscopy revealed an exophytic tumor of the sigmoid colon. Metastatic disease was not found in imaging studies. A low anterior resection was performed. The pathologic examination revealed a collision tumor consisting of a poorly differentiated adenocarcinoma of the colon and metastatic lobular carcinoma. The diagnosis was challenging due to the lack of a previous history. Also, the diffuse architectural pattern and signet ring cells found may be in primary signet ring carcinoma of the colon as well as in carcinomas from other anatomical sites. Immunohistochemistry was helpful in making the diagnosis. A review of the literature revealed that this is the fourth case of metastatic breast carcinoma coexisting with colonic adenocarcinoma.

Keywords: cdx-2; colon; colorectal carcinoma; gata-3; immunohistochemistry; lobular carcinoma; metastasis.

Figure 1. Poorly differentiated colonic adenocarcinoma displaying extracellular mucin production (white arrow) (HE x 100).

Abbreviation: HE: hematoxylin and eosin.

Figure 2. Diffuse type carcinoma cells display eccentric nuclei and intracytoplasmic lumina (white arrows) at high magnification (HE x 400).

Abbreviation: HE: hematoxylin and eosin.

Figure 3. Nests of poorly differentiated colonic carcinoma (white arrows) in close proximity to smaller neoplastic cells (black arrows) with a diffuse architectural pattern (HE x 100).

Abbreviation: HE: hematoxylin and eosin.

Figure 4. Lymph node infiltration by diffuse type carcinoma cells (white arrows) (HE x 100).

Abbreviation: HE: hematoxylin and eosin.

Figure 5. CDX-2 is diffusely positive in colonic carcinoma cells (white arrows) (CDX-2 x 100).

Figure 6. Diffuse type carcinoma cells were positive for GATA-3 (white arrows) while colonic adenocarcinoma cells were negative (GATA-3 x 100).