915 - Diagnostic Challenge of Shoulder Fibroma Presenting With Chronic Pain: A Case Report

A 65-year-old female presented with chronic, worsening right shoulder pain and swelling. Imaging revealed a large soft tissue mass and biopsy confirmed fibroma. Concurrent imaging and exam findings were consistent with rotator cuff syndrome and biceps tendinitis. She was given a subacromial steroid injection which for both diagnostic and therapeutic purposes.

Case Description:

The patient presented for chronic, diffuse right shoulder pain in January 2025. On exam, shoulder motion and strength were preserved. The right deltoid was enlarged and firm to palpation, and neurovascular status was intact distally. There was tenderness over the biceps groove and a positive Speed’s test. X-ray was unremarkable. MRI revealed a large soft tissue mass between the deltoid, teres minor, and infraspinatus muscles, concerning for a soft tissue tumor. MRI also showed supraspinatus tendinosis and a small partial tear of the distal subscapularis tendon. Biopsy of the mass confirmed a fibroma. Given the uncertainty of whether pain was attributable to mass effect or tendinopathy, a subacromial steroid injection was performed. Due to progressive enlargement, surgical excision of the fibroma was elected.

Discussions:

Fibromas of the shoulder are rare and can mimic more concerning soft tissue tumors such as sarcomas on imaging. Their clinical presentation may overlap with common shoulder pathologies, highlighting the importance of obtaining a thorough physical exam and clinical history. In this case, the patient’s primary pain generator was unclear, raising the question of mechanical mass effect versus intrinsic tendon pathology. Subacromial corticosteroid injection was pursued to clarify the contribution of rotator cuff pathology to symptoms.

Conclusions:

This case demonstrates the diagnostic challenge of space-occupying lesions. Fibromas, although benign, may present with pain and swelling resembling more common musculoskeletal etiologies or raise concern for malignancy. Careful integration of history, physical exam, and imaging is essential, with biopsy and multidisciplinary evaluation playing a critical role.