Nodular Fasciitis of the Piriformis Muscle Initially Concerning for Metastasis in a Patient With Previous History of Colon Adenocarcinoma: A Case Report

Ruchama Charles; Debajyoti Saha; Julia Jennings; Ali Akalin; George Watts; Mathew J Most

doi:10.1155/cro/8874014

Nodular Fasciitis of the Piriformis Muscle Initially Concerning for Metastasis in a Patient With Previous History of Colon Adenocarcinoma: A Case Report

Case Rep Orthop. 2026 Jun 10:2026:8874014. doi: 10.1155/cro/8874014. eCollection 2026.

Authors

Ruchama Charles¹, Debajyoti Saha², Julia Jennings³, Ali Akalin⁴, George Watts⁵, Mathew J Most⁶

Affiliations

¹ Department of Orthopedics and Physical Rehabilitation, UMass Chan Medical School, Worcester, Massachusetts, USA, umassmed.edu.
² Department of Radiology, UMass Chan Medical School, Worcester, Massachusetts, USA, umassmed.edu.
³ Department of Pathology, UMass Chan Medical School, Worcester, Massachusetts, USA, umassmed.edu.
⁴ Department of Pathology, UMass Memorial Health and UMass Chan Medical School, Worcester, Massachusetts, USA.
⁵ Department of Radiology, UMass Memorial Health and UMass Chan Medical School, Worcester, Massachusetts, USA.
⁶ Department of Orthopedics and Physical Rehabilitation, UMass Memorial Health and UMass Chan Medical School, Worcester, Massachusetts, USA.

Abstract

Case: We report a case of nodular fasciitis (NF) of the hip in a patient with a history of colon adenocarcinoma, concerning for metastasis. PET/CT showed a hypermetabolic lesion, and MRI revealed a well-defined, enhancing intramuscular mass. Histology identified fascicles of spindle or stellate cells with ovoid nuclei in myxoid and collagenous stroma with sparse inflammatory cells. On immunohistochemistry, the spindle cells expressed smooth muscle actin. Fluorescence in situ hybridization (FISH) demonstrated ubiquitin-specific protease 6 (USP-6) gene rearrangement, confirming the diagnosis.

Conclusion: NF is a benign, rapidly growing soft tissue lesion mimicking malignancy. Surgical excision is curative. Accurate diagnosis can prevent unnecessary interventions.

Keywords: case report; nodular fasciitis; peri-hip mass.