eP726 - Obstructing Signet Ring Cell Cecal Adenocarcinoma Complicated by Synchronous Rectal Cancer: A Case Report

Purpose/Background: Synchronous colorectal carcinoma occurs in approximately 4% of all colorectal carcinoma patients and is defined by the presence of two or more primary tumors diagnosed either at the same time or within six months of each other1. They present a treatment dilemma, especially when they are in different areas of the colon with different pathologies. We present the case of a 65-year-old female found to have an obstructing cecal adenocarcinoma with signet ring features and a synchronous mucinous adenocarcinoma of the rectum.Methods/Interventions: A 65-year-old female presented to the emergency department endorsing 5 weeks of solid food intolerance, 20-pound weight loss, and diarrhea. She denied melena or hematochezia, did not have abdominal pain, and denied prior intra-abdominal surgeries. She had a remote history of a prior spinal tumor that was treated with surgery and chemoradiation and had never had a colonoscopy. She also had hypertension, type 2 diabetes mellitus, and osteoarthritis. She did not have history of inflammatory bowel disease or family history of colorectal cancer. Her abdomen was non-tender, minimally distended, there was no palpable rectal mass.
At presentation, her WBC count was 11.2, Hgb 12.8, CEA 5.5, and her electrolytes were within normal limits. A CT of the chest, abdomen, and pelvis was performed showing a mechanical partial small bowel obstruction secondary to ileocecal mass. She then underwent a colonoscopy that showed an ulcerated cecal mass and a mass in the rectum, approximately 12cm from the anal verge. This rectal mass resulted as rectal adenocarcinoma. The cecal mass pathology showed poorly differentiated adenocarcinoma with signet ring cell features. Staging workup was completed showing a midrectal mass with multiple suspicious pelvic nodes, cT2N2a. All pathology was MMR proficient.
We did not want to leave the aggressive signet ring tumor in place while surgery was delayed for total neoadjuvant therapy (TNT). After multidisciplinary discussion, we proceeded with a laparoscopic right colectomy with end ileostomy to allow her to undergo chemoradiation for the pelvic mass. Pathology from the cecal mass showed invasive signet ring cell adenocarcinoma that extended into the appendix with extensive lymphovascular and perineural invasion as well as 8/15 positive lymph nodes, pT4aN2bM0. After recovering from her surgery, she underwent 12 cycles of FOLFOX and chemoradiotherapy.
She then had a flexible sigmoidoscopy showing residual tumor, a rectal cancer MRI showing minimal change in the lymph nodes and only mildly decreased size of her rectal mass. She was then offered her definitive operation and underwent a laparoscopic ultra-low LAR, ileostomy takedown with ileocolic anastomosis and end colostomy. Pathology resulted with moderately differentiated adenocarcinoma with mucinous features and 0/14 positive nodes (ypT2N0).Results/Outcomes: N/AConclusion/

Discussion: Survival with signet ring colon adenocarcinoma is poor, with a reported 5-year survival from 9-36%2. Survival difference in synchronous colorectal cancer is comparable to single tumor pathology. As she was obstructed from her cecal adenocarcinoma showing signet cell features, we elected to proceed with upfront resection, rather than performing a diverting loop ileostomy, to allow for treatment of her rectal cancer. We did not want to leave the aggressive tumor in place while she underwent TNT for her rectal cancer.