Background: Metastatic squamous cell carcinoma (SCC) to the axillary or inguinal lymph nodes from an unknown primary source is rarely encountered. We sought to evaluate a cohort of patients with metastatic SCC managed by lymphadenectomy to determine their survival and to determine which clinicopathologic factors were associated with outcome. Methods: All patients undergoing axillary or inguinal lymphadenectomy for SCC at our institution were identified retrospectively. Patients were stratified by unknown primary (UP) vs known skin primary (KP) tumors. Pertinent data on patient, tumor, and treatment variables was collected. Results: We identified 51 patients who met inclusion criteria. Of those, 20 patients (39%) had UP metastatic SCC and 31 patients (61%) had KP. The 5-year overall survival for UP was 65%, as compared to 49% for KP (p = 0.16). Cumulative incidence of recurrence was 46%. Cox regression failed to demonstrate a significant association between KP vs UP, HPV status, chemotherapy, or radiation with survival. Conclusions: Nearly two-thirds of patients undergoing axillary or inguinal lymphadenectomy for metastatic SCC of unknown primary were alive five years following the procedure.
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