Presentation
Diarrhea post 5-fluorouracil for metastatic colorectal cancer.
Patient Data
Right hemicolectomy. Mural thickening and mucosal hyperenhancement of the mid/distal small bowel to the enterocolic anastomosis. The colon is mildly thick-walled at the descending/sigmoid colon junction and the distal sigmoid and rectum.
Normal mesenteric venous and arterial enhancement.
Extensive omental nodularity with nodularity extending into the left anterior abdominal wall, consistent with port-site metastases, maybe from direct spread.
Small volume of pelvic, perihepatic and perisplenic free fluid.
This patient had a history of colorectal carcinoma, and on surveillance imaging developed omental nodules. They underwent a laparoscopic biopsy.
Histopathology
MACROSCOPIC: Omental biopsy – a piece of omentum 70 x 54 x 15mm in maximum dimension. A resection margin is evident along a portion of the circumference of the specimen. This was inked green. The surface of the omental fat demonstrates friable cream tissue measuring up to 50mm across. On sectioning, there is diffuse involvement of the omental fat by friable cream tissue. It has a slightly gelatinous cut surface.
MICROSCOPIC: All sections show metastatic mucinous carcinoma. Features of adenocarcinoma are seen with neoplastic glands present within abundant extracellular mucin. The cells are cuboidal to columnar forming poorly differentiated groups and strands. Tumor is widely seen within omental fatty tissue. Tumor extends to the serosal surface of the specimen. . Immunohistochemistry shows diffuse positive staining for CK20 and CDX2. The cells are negative for CK7. The features are consistent with metastatic colorectal carcinoma.
DIAGNOSIS: Omental biopsy: METASTATIC MUCINOUS ADENOCARCINOMA, with morphology and immunohistochemistry consistent with a colorectal primary.
Case Discussion
No other cause for enterocolitis was seen with no evidence on CT for an ischemic cause and laboratory testing for C. difficile toxin, norovirus and rotavirus was all negative. 5-fluorouracil (5-FU), an antimetabolite commonly used to treat cancers, can induce intestinal mucositis resulting in an enterocolitis picture on CT. This is the presumed cause in this patient.
Another important finding in this case, is the seeding of tumor along the laparoscopic port sites (i.e. port-site metastasis). This is a rare but important finding that can occur after laparoscopic surgery for various gastrointestinal, urogynaecological and other cancers.
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