A solitary omental lesion on contrast-enhanced computed tomography sparked concerns of metastatic recurrence in a 35-year-old man previously treated for stage II colorectal adenocarcinoma.
The patient presented with a three-month history of constipation but no weight loss or bleeding per rectum, according to a case report published by Cureus on November 13, 2026. A colonoscopy revealed an ulceroproliferative growth in the rectosigmoid region, and biopsy confirmed a moderately differentiated adenocarcinoma.
Following curative-intent treatment, post-treatment surveillance identified the new abdominal mass. A contrast-enhanced CT scan showed a well-defined lesion in the omentum that suggested cancer recurrence, but the patient's CEA level was normal at 13 ng/mL, and a PET-CT scan showed no abnormal F-18 FDG uptake.
Given the discordant clinical, biochemical, and radiological findings, medical teams performed an image-guided biopsy. Histopathological examination revealed fat necrosis without evidence of malignancy. The lesion subsequently resolved on follow-up ultrasonography.
Fat necrosis is a benign inflammatory process involving adipose tissue that can present as a mass and mimic malignant disease on imaging. It may occur following trauma, surgery, inflammation, pancreatitis, or vascular compromise. In patients previously treated for colorectal cancer, a newly identified omental mass raises distinct concerns for metastatic recurrence.
Colorectal cancer remains one of the common malignancies worldwide, and recurrence is an important concern following curative-intent treatment. A nationwide Danish cohort study of patients with stage I-III colorectal cancer demonstrated that recurrence continues to occur during post-treatment follow-up, highlighting the importance of regular surveillance.
Abdominal fat necrosis frequently mimics malignant lesions such as liposarcoma and peritoneal or omental metastases. Encapsulated fat necrosis was initially described in the breast in the 1970s, with subsequent medical literature characterizing nodular-cystic forms of the condition.
- Benign Mimickers: Fat necrosis is a harmless inflammatory response in fat tissue that can look identical to cancer on standard scans.
- Conflicting Results: When imaging suggests a tumor return, but blood markers and PET scans show normal activity, doctors investigate further with tissue biopsies.
- Biopsy Certainty: An image-guided tissue sample provides definitive proof, sparing patients from unneeded cancer therapies.
| Diagnostic Modality | Initial Finding | Clinical Interpretation |
|---|---|---|
| Contrast-Enhanced CT | Well-defined omental lesion | Suspicious for metastatic recurrence |
| Serum CEA Level | Within normal range (13 ng/mL) | Discordant with active malignancy |
| PET-CT Scan | No significant FDG uptake | Lacks hypermetabolic activity of cancer |
| Histopathology | Fat necrosis without malignancy | Definitive benign diagnosis |
Regular clinical and radiological surveillance remains essential for all individuals with a personal history of colorectal cancer.
- Musthafa A, Gopan G, Abraham B, et al. (November 13, 2026) Omental Fat Necrosis Mimicking Metastatic Recurrence in A Patient With Colorectal Cancer: A Case Report. Cureus 18(11): e119584. doi:10.7759/cureus.119584
