Osseous Sarcoid-like Reaction in Sigmoid Colon Cancer Requiring Differentiation from Bone Metastasis

Although sarcoid-like reactions are uncommon in colorectal cancer, they can coexist with other cancers. We herein report a 50-year-old woman with sigmoid adenocarcinoma and osseous sarcoid-like reactions that resembled metastases. Positron emission tomography-computed tomography revealed an uptake in the iliac bone and para-aortic lymph nodes. The depth of invasion indicates non-metastatic lesions. Bone and lymph node biopsies revealed epithelioid non-caseating granulomas with bone trabeculae, resulting in a final diagnosis of pathological T2N2aM0, Stage IIIB. When the expected depth of invasion differs from that of typical bone metastases, colorectal cancer-associated bone lesions should be evaluated for sarcoid-like reactions.