Splenic Solitary Metastasis From Melanoma Malignum: A Case Report

Melanoma is a malignant tumor derived from melanocytes, predominantly located in the skin and mucosal surfaces. Although this cancer can spread to multiple organs, isolated metastasis to the spleen is exceptionally uncommon. When splenic involvement does occur, it typically forms part of widespread systemic dissemination, rather than appearing as a solitary lesion. This report discusses a 62-year-old male who underwent elective splenectomy following the discovery of a suspicious splenic mass. Three years earlier, he underwent excision of a pigmented nodular lesion in the right pectoral region. Histopathology revealed superficial spreading melanoma, Clark III, Breslow II, with 0.8 mm margins and no lymphovascular invasion, microsatellitosis, or mitoses. Re-excision and right axillary dissection confirmed metastatic melanoma in one of eight lymph nodes. Examination of the resection margins of the re-excised specimen showed no evidence of increased melanocytic activity. A follow-up abdominal CT identified a 7 mm, well-circumscribed, hypodense lesion in the inferior pole of the spleen, which lacked contrast enhancement. Due to inconclusive findings on both CT and ultrasound, surgical removal of the spleen was performed. Subsequent histological and immunohistochemical evaluation confirmed the lesion to be metastatic amelanotic melanoma (ICD-O code M8770/6). Solitary metastasis to the spleen from melanoma remains a clinical rarity and often manifests several years after the initial diagnosis. In such cases, surgical excision is considered the preferred treatment, offering potential for extended survival in the absence of additional metastatic disease.