Synovial sarcoma in the plantar region: A case report and literature review

Synovial Sarcoma of the Hand and Foot: An Institutional Review

OBJECTIVES

Synovial sarcomas (SS) arising in distal extremities are rare and have been studied using mostly case reports and small series. We aimed to evaluate clinical presentation and survival outcomes for patients with hand or foot SS.

MATERIALS AND METHODS

We conducted a retrospective review of 84 patients diagnosed with primary hand (n=20) and foot (n=64) SS between 1979 and 2019. Progression-free survival (PFS), overall survival (OS), local recurrence-free survival and metastasis-free survival were estimated using the Kaplan-Meier method and log-rank test. Cox-proportional hazards regression was used to estimate the hazard ratios.

RESULTS

Of 84 patients, 63 (75%) presented with localized disease with 36 years median age at diagnosis (range: 4 to 76) and 21 (25%) with metastasis with 30 years median age at diagnosis (range: 15 to 64). Among patients presenting with localized disease, (1) 5 years-PFS, OS, local recurrence-free survival, and metastasis-free survival rates were 82%, 88%, 100%, and 86%, respectively. (2) Tumor size <3.0 cm corresponded to 95% 5 years-PFS (vs. 84% for 3.0 to 4.9 cm, 53% for ≥5.0 cm; P=0.007) and 100% 5 years-OS (vs. 77% for ≥3.0 cm; P=0.04). (3) Patients with ≥5.0 cm (vs. <3.0 cm) tumor size had 7.99 (95% confidence interval: 1.68, 37.91) times higher hazard of progression. Remarkably, patients presenting with metastasis had 50% 5 years-OS rate. Also, younger age (15 to 39 vs. 40 y and above) predicted better OS among patients presenting with localized disease (P=0.04) and with metastasis (P=0.03).

CONCLUSIONS

Survival outcomes are favorable for younger patients with <3.0 cm hand or foot SS. Local control is excellent, but we observed larger tumor size to be associated with poorer outcomes. Therefore, we recommend consideration of systemic therapy for patients with ≥3.0 cm hand or foot SS.

Primary cutaneous synovial sarcoma-Sometimes the hoof beats are zebras

Synovial sarcoma accounts for 5% to 10% of soft tissue sarcoma and it typically presents as a deep soft tissue mass. Primary cutaneous presentation is exceptionally rare, with only isolated case reports. We report a case of primary cutaneous synovial sarcoma in a 58-year-old woman that presented as a nodule involving the left occipital scalp. A complete radiologic evaluation of the patient failed to reveal any other mass lesion. Histologic sections showed a densely cellular, diffuse spindle cell proliferation within the subcutis. The lesion was composed of uniform, plump spindled cells with nuclei and vesicular chromatin, arranged in haphazard fascicles. There was admixed hemorrhage and a hemangiopericytoma-like vasculature. Immunohistochemically, the spindled cells showed focal strong positivity for cytokeratin (CK) OSCAR, CK5/6, CK34BE12, and pan-CK. Fluorescence in situ hybridization was positive for a rearrangement of SYT (SS18), confirming the diagnosis of monophasic synovial sarcoma. Synovial sarcoma should be considered in the differential diagnosis of monomorphous spindle cell tumors, especially if the tumors have a hemangiopericytoma-like vasculature or express keratins. In such cases, confirmatory molecular testing should be performed to confirm the diagnosis.

Synovial sarcoma mimicking a traumatic pseudoaneurysm in the upper extremity

Synovial sarcomas are a rare but aggressive malignancy that primarily affects young patients. Diagnosis is often difficult and delayed due to its insidious onset, heterogenous presentation and mimicry of other pathologies. We present the case of a patient with a history of a slow-growing left arm mass that arose after a traumatic fracture of the humerus. Multimodal imaging was undertaken and reported the mass as being consistent with a vascular malformation of the brachial artery. The patient underwent surgical repair of the artery and intraoperative biopsies confirmed a diagnosis of synovial sarcoma. This case highlights the importance of maintaining suspicion for soft-tissue sarcomas in young patients presenting with a mass, and demonstrates the way in which these tumours may mimic other pathologies both clinically and radiologically. Early referral to a specialist sarcoma centre is key for further investigative workup.