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

ABSTRACT

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 tumormuscle 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 tumormuscle 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.