Important Role of Ultrasound in Assessing Tubulocystic Renal Cell Carcinoma

Tubulocystic renal cell carcinoma is a rare renal neoplasm with imaging characteristics that may make it challenging to differentiate from benign cystic lesions. This retrospective single-institution study characterized the multimodality imaging features of pathologically confirmed tubulocystic renal cell carcinoma with emphasis on ultrasound (US) findings. Cases identified between 2016 and 2023 were reviewed for demographic, clinical, and imaging features on computed tomography (CT), magnetic resonance imaging (MRI), and US. Seven patients (6 male, 1 female; mean age 61 ± 8 y) were included, with presentations of abdominal pain (n=2), hematuria (n=1), and incidental detection (n=4). The mean maximal tumor diameter was 2.4 cm (range: 1.4-4.8 cm); 6 lesions were round and 1 was bilobed. On CT, masses demonstrated low attenuation (mean 15 HU) with variable enhancement (mean 23 HU). MRI in 5 cases demonstrated predominantly T1 hypointense and T2 hyperintense lesions, with 1 lesion showing mixed T2 signal intensity; 3 cases showed enhancement, including septa or a mural nodule. Two hyperechoic lesions demonstrated enhancement on MRI, with enhancement corresponding to the hyperechoic portions of the mixed echogenic mass. US in 5 cases showed 3 uniformly hyperechoic, 1 mixed echogenic, and 1 septated hypoechoic mass, all demonstrating posterior acoustic enhancement. CEUS in 1 case revealed septal enhancement. Although CT and MRI features may mimic cysts, US most commonly demonstrates a hyperechoic lesion with posterior acoustic enhancement and may provide important additional diagnostic information when other imaging findings are equivocal.