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

Sep 23, 2026

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Osseous sarcoid-like reactions are rare in colorectal cancer but may mimic metastatic disease. A 50-year-old woman with sigmoid adenocarcinoma developed osseous sarcoid-like lesions resembling metastases. Positron emission tomography-computed tomography showed uptake in the iliac bone and para-aortic lymph nodes, while invasion depth supported non-metastatic pathology. Biopsies from bone and lymph nodes demonstrated epithelioid non-caseating granulomas with bone trabeculae, leading to a final diagnosis of pathological T2N2aM0, Stage IIIB. When depth of invasion differs from typical bone metastases, evaluation for sarcoid-like reactions is recommended for accurate staging and treatment.

LanguageEnglish

CategoryHealthcare

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Introduction

Case report

Laboratory data and diagnostic workup

Colonoscopy and imaging findings

Staging and final diagnosis

doi: 10.2169/internalmedicine.4761-24 Intern Med 64: 2317-2322, 2025 [http://internmed.jp](http://internmed.jp) 【CASE REPORT】 Osseous Sarcoid-like Reaction in Sigmoid Colon Cancer Requiring Differentiation from Bone Metastasis Ayane Higashi 1, Hiroto Inoue 2, Hiroshi Matsumoto 3, Soichiro Tani 4, Kenji Isokawa 5, Hiroyuki Aoyama 3, Shuhei Shintani 3, Takayuki Imai 3, Masashi Ohno 3, Hidenori Kimura 2, Toru Miyake 4, Atsushi Nishida 1, Ryoji Kushima 3, Masaji Tani 2 and Osamu Inatomi 1 | Abstract:
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.
Key words: colon cancer, neoplasm metastasis, diagnosis, differential, sarcoid reaction, iliac bone
(Intern Med 64: 2317-2322, 2025)
(DOI: 10.2169/internalmedicine.4761-24) | | | --- | --- | |
Introduction | though it is uncommon in CRCs. Furthermore, most reports thus far have involved regional lymph nodes, with bone involvement being extremely uncommon. A misdiagnosis of | | Colorectal cancer (CRC) is the second-most common | sarcoid-like reactions as distant metastases can lead to inac- | | cause of cancer-related deaths worldwide (1) . Distant metas- | curate tumor staging and inappropriate treatment options. | | tasis has a poor prognosis, with the liver, lungs, and perito- | Therefore, accurate differentiation is crucial. However, dis- | | neum being the most common sites of metastases (2) . Bone | tinguishing between these two entities using imaging alone | | metastases were found in 6.6% of cases, and lung or liver | is difficult, and biopsies are typically required. | | metastases in 83%(3) . Detecting distant metastases is cru- | We herein report a patient with sigmoid colon cancer and | | cial for treatment selection, and surgical resection is gener- | bone lesions in whom a computed tomography (CT)-guided | | ally not recommended in the presence of distant metastases, | biopsy revealed a sarcoid-like reaction, allowing for appro- | | with chemotherapy being frequently used instead. However, the chances of achieving a cure with chemotherapy alone | priate surgical resection of CRC. | | are low. | Case Report | | A sarcoid-like reaction is characterized by the formation | | | of a localized noncaseating epithelioid cell granuloma in the | A 50-year-old woman presented to our hospital with rec- | | absence of sarcoidosis. It frequently coexists with malignan- | tal bleeding. The patient had no significant medical or fam- | | cies, where tumor antigens activate the host immune response, resulting in the formation of this granulomatous le- | ily history. Blood tests revealed iron deficiency anemia (Hb 9.2 g/dL), but the tumor marker CEA (0.5 ng/mL) and CA | | sion (4) . This reaction occurs in 4 .4% of solid tumors, al- | 19-9 (13 U/mL) were within normal limits (Table 1) . | 1 School of Medicine, Shiga University of Medical Science, Japan, 2 Department of Endoscopy, Shiga University of Medical Science, Japan, 3 Division of Gastroenterology, Department of Medicine, Shiga University of Medical Science, Japan, 4 Department of Surgery, Shiga University of Medical Science, Japan and 5 Department of Pathology, Shiga University of Medical Science, Japan Received: September 23, 2024; Accepted: November 21, 2024; Advance Publication by J-STAGE: February 1, 2025 Correspondence

FAQs

Why was differentiation from bone metastasis important in this case?

Osseous sarcoid-like reactions can resemble metastatic lesions on imaging, which can lead to inaccurate tumor staging and inappropriate treatment. Accurate differentiation is therefore crucial.

What did imaging show in the patient with sigmoid colon cancer?

Positron emission tomography-computed tomography revealed uptake in the iliac bone and para-aortic lymph nodes. Contrast-enhanced CT showed thickening of the sigmoid colon wall without evidence of invasion beyond the muscularis propria, supporting T2 staging.

How was the final diagnosis established?

Bone and lymph node biopsies showed epithelioid non-caseating granulomas with bone trabeculae. Together with invasion depth findings, this supported pathological T2N2aM0 (Stage IIIB) rather than true metastasis.

Sep 23, 2026

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