Table 5 Solid/ non papillary tumors, with predominant eosinophilic cells
| Typical histology | Expected immunoprofile | Recommendation | |
|---|---|---|---|
| Oncocytoma | abundant oncocytic cytoplasm, growing in cords, nests, alveoli and tubules in fibrous/ myxoid stroma. Degenerative atypia can occur but no papillary growth, clear cell and necrosis |
CD117+ CK7(−) |
- No IHC needed if typical morphology - rule out SDH deficient before dx of Oncocytoma in a young patient. |
| 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 |
| 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 |
| SDH-defficient | diffuse solid growth, entrapped preexistent tubules, and foci of tubular and nested growth. The most characteristic finding is a vacuolated cytoplasm or granular flocculent appearance. It is usually of low-grade morphology |
SDHB loss PAX8+ AE1AE3(−)/f+ CAM5.2 (−)/f+ CK7(−)/f+ EMA (−)/f+ CD117(−) CAIX(−) RCC(−) | SDH germline mutation testing for patients with familial RCC and pheochromocytoma or those with characteristic SDHB-deficient pathologic pattern or oncocytic kidney tumors coexistent with GIST, pheochromocytomas or paragangliomas. |
| Tubulocystic | Grossly a multicystic mass. At microscopy, small and medium sized tubules with occasional cysticaly dilated tubules, lined by cells with eosinophilic/oncocytic cytoplasm and prominent nucleolus |
CK7+ Racemase+ FH+ 2SC+ |
- No IHC needed if typical morphology. - Report poorly differentiated areas and perfor FH and 2SC in such cases. |
| ACKD-associated carcinoma | May be multifocal or bilateral. Histology shows a mixture of acinar, alveolar, tubular, papillary, solid and multicystic patterns, with characteristic sieve-like and microcystic areas with oxalate crystals. | - No IHC needed if typical morphology. | |
| Angiomyolipoma | combination of bland morphologies of adipose tissue, smooth muscle tissue and large vessels with thickened walls. Epithelioid AML (> 80% epithelioid morphology) may behave aggressively. |
PAX-8 (−) AE1AE3 (−) AML+ HMB45+ MelanA+ Catepsin K+ |
- germline TSC1 and TSC2 are recommended - evaluate TFE3 or TFEB by IHC or FISH if MiT-family translocation RCC is in the differential |
| Low grade oncoytic tumor | solid sheets and compact nests of low grade oncocytic cells, with gradual transition to trabecular areas, sharply delineated edematous stromal areas with loose cell growth |
CD117(−) CK7+ | - Perform IHC to confirm morphology |
| High grade oncocytic tumor | oncocytic cells with high-grade nuclei, and prominent intracytoplasmic vacuoles. Well-circumscribed, non-encapsulated tumors, with solid to nested growth and focal tubulocystic features |
CD117+ CK7+ (scattered) Catepsin K+ CD10+ |
- Perform IHC to confirm morphology - germline TSC1 and TSC2 are recommended |
| ESC RCC | Female predominance. Grossly alternating solid and cystic areas of cells with eosinophilic and granular cytoplasm. Solid areas exhibit sheets, nests or acini, usually with adjacent cystic areas. Intracytoplasmic vacuoles and psammoma bodies may be present |
PAX8+ CK20+ Vimentin+ CK7(−) CD117(−) |
- Perform IHC to confirm morphology - germline TSC1 and TSC2 are recommended |