Epithelioid angiomyolipoma (EAML) is a rare variant of renal angiomyolipoma characterized by the predominance of epithelioid cells and an absence or paucity of mature adipose tissue. Unlike classic AMLs, which are benign and often asymptomatic, EAML has malignant potential, including local recurrence, vascular invasion, and distant metastasis. Due to its radiologic similarity to renal cell carcinoma (RCC), preoperative diagnosis remains challenging, and definitive diagnosis often relies on histopathological and immunohistochemical findings following surgical excision.

A 41-year-old male with a history of gout was incidentally found to have a renal mass during a routine health checkup in August 2023. Abdominal ultrasound revealed a 5.9 cm hypoechoic lesion at the lower pole of the left kidney, exhibiting increased vascularity. Subsequent contrast-enhanced computed tomography showed a 6.4 cm heterogeneously enhancing renal mass without evidence of extra-renal extension or lymphadenopathy. Initial laboratory findings revealed preserved renal function (Cr 1.0 mg/dL, eGFR 84.6 mL/min/1.73m²). Given the radiologic suspicion of RCC, the patient underwent robotic-assisted partial nephrectomy (RAPN) on October 4, 2023. Histopathology revealed features consistent with epithelioid angiomyolipoma, including sheets of epithelioid cells with eosinophilic cytoplasm and immunoreactivity for melanocytic markers such as HMB-45, confirming the diagnosis. The patient’s postoperative recovery was smooth, and he remained asymptomatic. Renal function was stable across serial follow-ups, with no radiographic evidence of recurrence on CT and ultrasound up to 2 years postoperatively.

Epithelioid angiomyolipoma (EAML) is a rare renal tumor that can mimic renal cell carcinoma (RCC) due to its lack of macroscopic fat and atypical imaging features. Because of its potential for malignant behavior, including recurrence and metastasis, early surgical intervention is recommended. In this case, robotic-assisted partial nephrectomy provided both diagnostic clarity and effective treatment. Histopathology confirmed EAML, and the patient remained recurrence-free postoperatively.

This case emphasizes the importance of considering EAML in the differential diagnosis of atypical renal masses and highlights the value of nephron-sparing surgery.