eP677 - Recurrent Secondary Colorectal Metastasis: A Rare Case Report

Purpose/Background: Colorectal (CR) cancer (CA) is the 3rd most common primary cancer worldwide. Contrarily, secondary metastasis to the colon and rectum are exceptionally rare and documentation of the incidence is limited. Secondary CR metastasis accounts for less than 1% of CR malignancies with common primary sites including ovary, lung, breast, skin, and prostate (2). Pathogenesis involves direct spread via peritoneal seeding as seen in ovarian CA, although lymphatic and hematogenous spread is also described (1). Presentation can be non-specific ranging from asymptomatic to obstruction and perforation making diagnosis challenging. We highlight the case of a woman with 2ry colorectal metastasis with a primary breast CA diagnosed incidentally on routine colonoscopy with subsequent metachronous obstructing mass.Methods/Interventions: Patient with hx of breast CA treated with breast conservation, radiation, and endocrine therapy over 10 years ago. 7 years post diagnosis she was found to have abnormal vascularity and nodularity in the cecum on screening colonoscopy. Pathology consistent with metastatic lobular carcinoma. She was treated with hormone therapy and right hemicolectomy.
3 years later, she presented with abdominal pain, fecal incontinence, and mucus discharge. Rectal exam showed partially obstructing and fixed rectal mass. CT C/A/P revealed circumferential rectal wall thickening, perirectal and presacral subcentimeter nodes. Sigmoidoscopy showed a large circumferential near obstructing mass 4 cm from anal verge. Lesion appeared submucosal with inflamed mucosa. Pathology showed metastatic breast CA. She underwent exploratory laparotomy and diverting loop colostomy.
Patient returned with high grade SBO failing to resolve conservatively. She underwent ex lap and found the small bowel adhered in the pelvis, and a stricture near the previous ileocolic anastomosis. Lysis of adhesions was done, and anastomosis revised. Surgical pathology revealed metastatic breast CA invading the subserosa with 2 of 15 lymph nodes positive. Patient opted to pursue hospice care.Results/Outcomes: Secondary colorectal tumors represent a rare entity in literature and majority documented through case reports and limited retrospective studies. A significant percent of data is gathered via autopsy reports. In a 10-year autopsy review of 16000 cases, 62 had evidence of 2ry CR metastasis (3). Similarly, DiSibio and French, demonstrated that stomach, small intestine, and colon 2ry metastasis combined accounted only for 3% of cases in a review of 3827 autopsies.
Breast CA appears to be the more common primary malignancy in 2ry CR metastasis. A review of publications totaling 162 cases of metastatic spread to the rectum, identified sixteen different primary malignancies. Breast CA was the most common, found in 46 of the cases reviewed (4). Likewise, retrospective review of endoscopic diagnosis of 2ry GI metastasis, found breast CA to be the most common primary. Although there was higher incidence of breast CA metastasis to the upper GI tract, breast CA was still higher in the colon and rectum compared to others (5). Despite these findings, metastasis of breast CA to the GI tract is still significantly rare.Conclusion/

Discussion: This case review exemplifies the unusual phenomenon that is 2ry metastasis to the colon and rectum. Although incidence is low, it is important to have a heighten sense of suspicion in patients with known malignancies. With advances in management of breast CA and improved overall survival, it will not be surprising for these numbers rise.