Primary Renal Glomus Tumor of Uncertain Malignant Potential: A Rare Case Report and Literature Review.
Renal glomus tumor (GT) is a rare neoplasm originating from glomus cells within the kidney. The subtype designated as uncertain malignant potential (UMP) is particularly rare, with limited literature available. Its clinical presentation and imaging features closely resemble those of renal cell carcinoma (RCC), making accurate preoperative diagnosis difficult. This case report aims to describe the clinical, radiological, and pathological features of a renal GT of UMP and to summarize previously reported cases to improve recognition of this rare entity. We report a case involving a 36-year-old male who was incidentally found to have a cystic-solid mass (5.8 × 5.1 × 4.2 cm) in the lower pole of the right kidney during evaluation for tinnitus. Contrast-enhanced CT suggested a diagnosis of RCC, prompting laparoscopic partial nephrectomy. Postoperative pathology revealed focal mild cellular atypia and a Ki-67 proliferation index of approximately 10%. Immunohistochemistry showed positivity for SMA and Collagen IV, focal positivity for CD34, and negativity for CD10, HMB45, Melan-A, Desmin, CK, and CK7. Based on histomorphology and immunoprofile, a diagnosis of primary renal GT with UMP was established. The patient recovered well postoperatively without further treatment, and no local recurrence or distant metastasis was observed during an 8-month follow-up. We reviewed the existing literature to summarize the clinical characteristics and diagnostic considerations of UMP-type renal GT, aiming to enhance recognition of this rare entity.