To analyse imaging features and the differential diagnosis of eosinophilic solid and cystic renal cell carcinoma (ESC-RCC) .

The current study retrospectively reviewed the imaging features of seven patients (4 male, 3 female; age range: 25-70 years; median age: 46 years) diagnosed with ESC-RCC at our institution from March 2020 to October 2024.

Six patients presented with unilateral and solitary lesions, one patient (1/7, 14.3%) exhibited bilateral multifocal lesions. The tumour size ranged from 2.0 to 8.5 cm, with a mean diameter of 4.0±2.1 cm. Most (5/8, 62.5%) tumours showed high and low mixed density on non-contrast CT scans. The remaining tumors exhibited the following characteristics: one presented as homogeneous isodensity, another as hypodense with foci of hyperdensity, and a third as slightly hyperdense with small areas of hypodensity. On contrast-enhanced CT, 75% (6/8) of the tumours demonstrated heterogeneous enhancement with peak CT values in the corticomedullary phase for four cases and in the nephrographic phase for two. Of the remaining two, one displayed a gradually progressive enhancement pattern with peak enhancement in the nephrographic phase, while the other showed mild enhancement. All (8/8) tumors were well-demarcated, with 75% (6/8) causing adjacent vascular compression and 87.5% (7/8) showing floating vessels. Tumour classification indicated that most tumours (37.5%) were categorized as type III, with types II and IV each comprising two cases, and type I included only one. Microscopically, all tumours were well-demarcated and lacked a capsule, lymph node metastasis, hemorrhage, calcification and necrosis.

ESC-RCC should be considered when encountering a well-defined cystic-solid lesion without calcification, haemorrhage, or fat, and the solid component shows various enhancement with the degree of enhancement less than that of the adjacent renal cortex in all phases.