Work

Absence of Viable Tumor Cells in Macroscopically Pigmented Regional Lymph Nodes after Immune Checkpoint Inhibitor Therapy in Duodenal Metastasis of Cutaneous Melanoma: A Case Report

Year: 2026

Type: article

Abstract: INTRODUCTION: Malignant melanoma frequently metastasizes to the gastrointestinal tract, but duodenal metastasis is uncommon, and pancreaticoduodenectomy (PD) for this indication is rare, particularly in the era of immune checkpoint inhibitors (ICIs). Moreover, the histological consequences of ICI therapy within regional lymph nodes draining gastrointestinal metastasis remain poorly documented. CASE PRESENTATION: A 67-year-old woman with a history of cutaneous malignant melanoma of the thumb developed metachronous ileocecal and duodenal metastases years after the initial resection, during treatment with ICIs. After ICI therapy, she underwent subtotal stomach-preserving PD for the duodenal metastasis. Although preoperative PET/CT showed no regional nodal uptake, the peripancreatic lymph nodes appeared macroscopically black, mimicking nodal metastasis. Histopathological examination revealed fibrosis with CD68-positive, melanin-laden macrophages and no viable tumor cells; Melan-A was negative, and Berlin blue staining excluded hemosiderin, confirming that the pigment was melanin. No viable tumor cells were identified within the regional lymph nodes. The postoperative course was uneventful. CONCLUSIONS: Macroscopically pigmented "black nodes" after ICI therapy may not represent viable metastasis, and detailed pathological evaluation is essential to avoid misinterpretation. This case also raises the possibility of an immunological role for tumor-draining lymph nodes during ICI therapy, although the implications for the timing of lymph node dissection remain uncertain.

Source: Surgical Case Reports

DOI: 10.70352/scrj.cr.26-0580