Rhabdoid Melanoma Solitary Metastasis to Kidney with Renal Vein Invasion Mimicking Renal Cell Carcinoma

Abstract

Abstract Introduction/Objective 83 percent of malignant melanoma cases present as localized skin lesions. However, a small percentage of patients present with concurrent metastatic disease or experience late metastasis. Metastatic melanoma has highly variable presentation and morphology, frequently mimicking other tumors. The most common metastatic sites in order of frequency are skin and subcutaneous tissue, lungs, liver, bones, and brain. While rare, metastasis to the kidney can occur and typically takes the form of multiple micrometastases. Methods/Case Report Here we present an unusual case of a late, purely rhabdoid large solitary renal metastatic melanoma with renal vein invasion, mimicking rhabdoid renal cell carcinoma. The patient is an 84 year old male with a remote history (30 years) of cutaneous malignant melanoma who was referred with a CT scan demonstrating 7.9 x 5.7 x 5.7 mass in the lower pole of the left kidney with a tumor thrombus in the renal vein hhighly suspicious radiographically for renal cell carcinoma. The patient underwent a radical nephrectomy. Macroscopically there was a solitary 7.7 x 6.3 x 5.5 cm tan-grey mass in the lower pole with gross invasion into the renal sinus fat and renal vein resembling the macroscopic appearance of a renal cell carcinoma. Microscopic examination demonstrated pleomorphic tumor cells with pure rhabdoid morphology, extensive necrosis and Lymphovascular invasion. No pigment was identified. No classic clear cell areas were identified. Immunohistochemical stains were positive for S100, SOX10 Melan-A, HMB45 and vimentin and negative for AE1/3, CK7, CAIX, PAX8, P63, CD117 and AMACR. Multiple resected lymph nodes were negative for metastasis Results (if a Case Study enter NA) NA. Conclusion This case is a rare and unusual presentation of melanoma, and it’s important to keep this diagnosis in consideration in the setting of unusual morphology of renal tumors.