Track
Case ReportsAbstract
PET/CT imaging is often used in the staging work-up of patients with advanced-stage melanoma. Non-malignant processes with increased metabolic activity can lead to false-positive findings, sometimes requiring histopathologic examination for definitive characterization. Cases with concurrent metastases and benign findings are uniquely challenging. We aim to highlight the importance of documenting non-malignant histologic findings concurrent with metastases so care teams are aware of potential confounders. We present two patients with metastatic melanoma and FDG-avid lymph nodes found on histopathologic examination to have both metastasis and benign processes. One patient had scalp melanoma with left pre-auricular lymph node metastasis confirmed by fine needle aspiration (FNA). After clinical progression following immunotherapy, PET/CT showed multifocal nodal disease in the chest and abdomen, likely metastatic. FNA of multiple pulmonary nodes showed non-necrotizing granulomas; left neck dissection showed metastatic melanoma and non-necrotizing granulomas. Another patient had vulvar melanoma with positive sentinel node. She underwent immunotherapy, radiotherapy, and lymph node excision. Subsequent PET scan showed hypermetabolic left inguinal and left axillary nodes consistent with metastatic disease. Upon excision, the inguinal node showed metastatic melanoma; the axillary node showed foreign material and giant cells. For both patients, benign FDG-avid nodes were located beyond the locoregional lymph node basin, leading to a false impression of stage IV disease. After histologic confirmation that the FDG activity was benign, these patients were appropriately staged and treated accordingly. In cases with metastases and non-malignant findings, pathologists should document the extent and location of both for accurate clinical and radiologic correlation.