P1240 - Cancer of Unknown Primary Presenting With Colorectal Metastases

Christopher Tricarico, MD¹, Zachary Sherman, MD², David Wan, MD^3
1New York-Presbyterian/Weill Cornell Medical Center, New York, NY; ²New York Presbyterian - Weill Cornell Medical Center, New York, NY; ³New York Presbyterian Weill Cornell Medicine, New York, NY

Introduction: Colorectal (CR) metastases are an uncommon, though underdiagnosed manifestation of malignancy. There remains a paucity of data to help clinicians understand and identify this clinical entity.

Case Description/Methods: A 39-year-old female presented with new onset seizure and was found to have widely metastatic carcinoma of unknown primary (CUP). A PET scan showed diffuse FDG-avid lymphadenopathy and innumerable osseous lesions. An LP showed leptomeningeal disease. EGD was unremarkable. Colonoscopy identified two 2-3mm sessile polyps as well as a 3mm mucosal nodule in the ascending colon which were biopsied with cold forceps. There was also a 12mm sessile polyp in the transverse colon that was incompletely resected using a lift and cut technique with a hot snare. Pathology from all four samples showed high-grade adenocarcinoma with focal signet-ring cells, extensively infiltrating the lamina propria. IHC was undiagnostic for a tissue of origin but was thought to be most consistent with a gynecologic malignancy. She underwent 7 cycles of carbo/taxol before deferring further treatment for palliative care.

Discussion: Metastatic lesions to the colon have been estimated to comprise just 1% of total colorectal cancers (1). However, postmortem studies and improved radiographic techniques have suggested that the incidence is higher (2). Multiple malignancies can metastasize to the colon including lung, ovarian, breast, prostate, renal cell carcinoma, and melanoma (1,3,4). Up to 30% of patients with CR metastases are asymptomatic (1) and metastases can spread diffusely below the epithelial layer as was the case with our patient. The development of metastases is a much more stochastic process compared to the stepwise progression from polyp to adenocarcinoma in primary colorectal cancer, and CR metastases may develop rapidly in the interval between screening colonoscopies. Prompt diagnosis of CR metastases provides information on disease extent which can inform prognoses and dictate optimal treatment strategies. Early detection of CR metastases can also help prevent complications such as obstruction, perforation, and bleeding. This case highlights the importance of maintaining a high degree of suspicion for CR metastases even in patients with atypical presentations of malignancy as well as the need for further research to identify tumor and pre-metastatic niche specific factors that predispose to CR metastases.


Figure: Figure 1: Colonoscopy pictures. a) Mucosal nodule found in the ascending colon (yellow arrow). b) Sessile polyp found in the ascending colon. c-d) Multiple views of the 12 mm sessile polyp found in transverse colon. e) Lift of the ascending colon polyp was done with Eleview. f) Transverse colon polyp status post polypectomy.


Disclosures:
Christopher Tricarico indicated no relevant financial relationships.
Zachary Sherman indicated no relevant financial relationships.
David Wan indicated no relevant financial relationships.


Christopher Tricarico, MD¹, Zachary Sherman, MD², David Wan, MD³. P1240 - Cancer of Unknown Primary Presenting With Colorectal Metastases, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.