Small soft tissue masses indeterminate at imaging: histological diagnoses at a tertiary orthopedic oncology clinic

Objective To review histologic diagnoses of soft-tissue masses (STMs) ≤ 2 cm with indeterminate imaging features encountered in musculoskeletal oncology clinic at a tertiary referral center. Materials and methods This was an IRB-approved retrospective review of patients with STMs ≤ 2 cm, referred to our tertiary care orthopedic oncology clinic over 4.75 consecutive years. Maximum diameter was based on imaging measurement by a fellowship-trained musculoskeletal radiologist. Simple lipomas, synovial cysts, metastases, and cases without histologic confirmation were excluded. Patient demographics, tumor imaging features (location, depth, size, and tumor:muscle enhancement and T2 signal ratios), and histology were recorded and compared. Results Mean maximum diameter for 42 trunk/extremity STMs was 1.5 cm (range, 0.7 to 2 cm). Mean age was 48 years (range, 18–83 years). Nine (21%) of the masses were malignant, while 33 (79%) were non-malignant. Thirty-nine (93%) of masses were superficial; 7/39 (18%) of these superficial tumors were malignant. Malignancy was not associated with underlying vessels, tendon, or fascia ( p = 0.19). The non-malignant vs. malignant tumor:muscle enhancement ratio was 2.15 vs. 2.32 ( p = 0.58) and enhancement coefficient of variation was 0.14 vs. 0.10 ( p = 0.29). Most common malignant histologic subtypes were synovial sarcoma ( n = 3), fibroblastic/myofibroblastic sarcoma ( n = 2), leiomyosarcoma ( n = 2), myxofibrosarcoma ( n = 1), and angiomatoid fibrous histiocytoma ( n = 1). The majority (67%) of non-malignant lesions were: leiomyoma ( n = 6), angiomyoma ( n = 5), schwannoma ( n = 4), benign fibrous histiocytoma ( n = 4), and hemangioma ( n = 3). Conclusions At a tertiary musculoskeletal oncology referral clinic, primary STMs ≤ 2 cm with indeterminate imaging features should be managed cautiously despite their small size and/or superficial location.