Cystic nephroma

A cystic nephroma, also known as multilocular cystic nephroma, mixed epithelial stromal tumour (MEST) and renal epithelial stromal tumour (REST),[1] is a type of rare benign kidney tumour.

They are typically discovered on medical imaging incidentally (i.e. an incidentaloma).

Cystic nephromas are diagnosed by biopsy or excision.

It is important to correctly diagnose them as, radiologically, they may mimic the appearance of a renal cell carcinoma that is cystic.

[2] The characteristics of cystic nephromas are: Cystic nephromas have an immunostaining pattern like ovarian stroma; they are positive for:

High magnification micrograph of a cystic nephroma showing the characteristic simple epithelium with hobnail morphology, and the ovarian -like stroma . H&E stain .
Histopathologic types of kidney tumor, with relative incidences and prognoses. Cystic nephroma is seen at bottom right in pie chart.