Table 1 Solid, non-papillary tumors with predominant clear cells

Clear cell

Clear or granular cytoplasm organized in acinar, alveolar, tubular, solid/cords and small cysts, within a delicate network of capillary vessels, intimately associated with the tumor. Eventually high-grade areas, necrosis, and sarcomatoid/ rhabdoid morphology

CD117(−)

CAIX+

RCC+

CD10+

Vimentin+

(CK7 may be + in higher grade areas)

- Perform IHC panel when other entities are in the differential

Chromophobe

Large eosinophilic vegetal-like cells, in finely granular cytoplasm, perinuclear halos and raisinoid atypical nuclei. Nuclear grade does not apply. Typically solid with parenchymal extension, entrapping tubules. Nests, broad alveoli and trabeculae may be seen.

CD117+

CK7+

- Confirm with diffuse CK7 if not typical morphology.

- Upon a hybrid Onco/Chrom or Clear cell/Chrom tumor, consider evaluation of germline FLCN mutation

Multilocular cystic renal neoplasm of low malignant potential

Cysts are lining by cells with clear cytoplasm and low-grade (ISUP 1 or 2) nuclei. The septae between cysts may contain some cords of clear cell but without expansive nodules (solid growth). Necrosis, vascular invasion, and sarcomatous transformation are incompatible with this diagnosis

CD10 +/−

CAIX +

CK7+(92%)

Racemase −/+

34bE12 -

- No IHC needed if typical morphology

- Perform IHC panel when CCRCC or CCPRCC (CAIX, 34bE12 and CK7) are in the differential

TCEB1 mutated

Multinodular appearance. Tumor aggregates intermixed with thick fibrous or fibromuscular bands. Low grade clear cells (no reverse polarity of nuclei). Nested and tubular growth with focal solid and papillary growth.

CAIX+

CK7+

Confirm with:

- TCEB1 mutation

- Chromosome 8 monosomy