Case report: Trapezius Fibromatosis in the Elderly - An Extremely Rare Tumor

Musculoskeletal fibromatoses represent a wide spectrum of fibroblastic and myofibroblastic neoplasms with similar pathologic appearances and variable clinical behavior. These lesions are categorized by location (superficial or deep). Deep fibromatosis in adults is divided into desmoid and abdominal wall type. Desmoid-type fibromatosis typically manifests as a deeply seated but poorly circumscribed soft-tissue mass. Slow insidious growth is common, and lesions are usually painless. It occurs most frequently in patients in the 2nd-4th decades of life, with a peak incidence between the ages of 25 and 35 years. Overall, the disease has a female predilection.

Herein, we present the case of a 78-year-old man who developed a gradually progressive painless swelling over the right side of the neck over a period of 6 months. The patient was planned for a magnetic resonance imaging scan which showed ill-defined lobulated mass in the right trapezius of size 4 × 7 × 5.4 cm, which was heterogeneous in T2, isointense in T1, multiple ovoid calcifications, and was suspected with cysticercosis or fibroma. Open biopsy was done a week later which was suggestive of fibromatosis. The patient underwent definitive resection of the tumor 1 week later and the tumor was found to be restricted to the muscular plane. Histology was consistent with fibromatosis, the specimen being positive for vimentin, beta-catenin, and smooth muscle actin. The patient was on serial follow-ups and the last follow-up, 3 year later did not show any signs of recurrence of the tumor.

This case report is being presented to highlight the radiological differential of cysticercosis in a patient with muscular fibroma, extremely rare presentation of fibromatosis of the trapezius in the 7th decade.