# Ossifying Fibromyxoid Tumor of the Shoulder: A Case Report

## TL;DR

A rare tumor called ossifying fibromyxoid tumor was diagnosed in a 61-year-old man through surgical excision and histopathology.

## Contribution

This case report highlights the diagnostic process and management of a rare tumor with intermediate malignant potential.

## Key findings

- OFMT was confirmed through histopathology and immunohistochemistry in a patient with a slowly growing shoulder mass.
- The patient underwent wide excision and has a benign postoperative course.
- Early diagnosis and proper excision are critical for managing tumors with potential for recurrence or metastasis.

## Abstract

Ossifying fibromyxoid tumor (OFMT) is a rare, slow-growing, mesenchymal tumor with intermediate malignant potential, predominantly affecting middle-aged individuals. Histologically, it presents as a fibrous capsule or pseudocapsule, with a complete or incomplete lamellar bone shell surrounding oval/polygonal cells within a fibromyxoid matrix. Advances in immunohistochemistry have facilitated OFMT identification, with S100 protein expression and INI-1 loss being notable features. CD10 expression is also reported in a small minority of cases. Recent studies highlight a translocation of the PHF-1 gene, proposing a possible etiology for tumorigenesis. Treatment involves wide excision, with long-term follow-up for recurrence or metastasis.

In this case, a 61-year-old White male presented to the outpatient surgical office with a painless mass on his right shoulder. The patient reported that the mass first appeared three to four years prior and that it had been growing slowly since the initial presentation. On examination, the patient had a well-circumscribed, 1.5 x 1.5 cm, soft, nontender, nonmobile subcutaneous mass on his right shoulder. The mass was initially suspected to be a subcutaneous cyst based on physical exam, but surgical excision and histopathology established the diagnosis of OFMT that extended to the margins of the specimen. The patient underwent a wider excision for margins and has had a benign postoperative course. The patient was referred to dermatology and oncology for continuation of care.

This case demonstrates the necessity for a thorough work-up, appropriate excision, and histopathologic examination to rule in diagnoses of lower incidence with the potential for a worse prognosis. Appropriate and timely diagnoses can guide proper screening for cancer recurrence and management.