Among the most common useful stains are cytokeratin 7 (separating clear cell RCC [negative] from papillary RCC, clear cell papillary RCC, and multilocular cystic RCC [positive] as well as separating chromophobe RCC [diffusely positive] from oncocytoma [focally positive/negative]) and CD117 (separating chromophobe RCC and oncocytoma [positive] from granular variants of clear cell RCC [negative]).
In low-grade nonpapillary eosinophilic neoplasms, distinction between oncocytoma and low-grade RCC mostly rests on histomorphology; however, cytokeratin 7 immunostain may be helpful.
Among the most common useful stains are cytokeratin 7 (separating clear cell RCC [negative] from papillary RCC, clear cell papillary RCC, and multilocular cystic RCC [positive] as well as separating chromophobe RCC [diffusely positive] from oncocytoma [focally positive/negative]) and CD117 (separating chromophobe RCC and oncocytoma [positive] from granular variants of clear cell RCC [negative]).
Material from 12 female and 15 male patients (13 granular cell tumours of the sellar region, 10 pituicytomas, four spindle cell oncocytomas) collected in the German Registry of Pituitary Tumours between 1993 and 2015 was re-evaluated according to the current WHO classification of tumours of the central nervous system and supplementary immunohistochemistry including S100-protein, CD56, CD68, thyroid transcription factor-1 (TTF-1), and Ki-67 was performed.
Oncocytomas activate 5' adenosine monophosphate-activated protein kinase (AMPK) and Tp53 (p53) and display disruption of Golgi and autophagy/lysosome trafficking, events attributed to defective mitochondrial function.
Atg7 deficiency alters progression of Braf(V600E)-driven tumors from adenomas (Braf(V600E); atg7(-/-)) and adenocarcinomas (trp53(-/-); Braf(V600E); atg7(-/-)) to benign oncocytomas that accumulated morphologically and functionally defective mitochondria, suggesting that defects in mitochondrial metabolism may compromise continued tumor growth.
Statistical analyses comparing the different expression of S100A1 in clear cell and chromophobe renal cell carcinomas observed by immunohistochemical and RT-PCR methods showed significant values (P<0.001), such as when comparing by both techniques the different levels of S100A1 expression in chromophobe renal cell carcinomas and oncocytomas (P<0.001).
Immunohistochemical expression of KIT was found in most chromophobe RCCs (95% in TMAs and 96% in conventional sections) and oncocytomas (88% in TMAs and 100% in conventional sections) but was infrequently observed in renal angiomyolipomas (17%), papillary RCCs (5%), and clear-cell RCCs (3%).
Fifty-five tissue samples (15 clear cell RCCs, 15 papillary RCCs, 7 chromophobe RCCs, 8 oncocytomas and 10 normal renal tissues) were studied The gene expressions of S100A1 and KIT were analysed by one-step RT-PCR by using the specific primers.
We found that 24 chromophobe RCCs (83%) and 5 renal oncocytomas (71%) revealed membranous immunoreactivity for KIT while none of the RCCs of other types expressed KIT immunohistochemically.
Mutations in the VHL gene were found in 54% of clear cell renal cell carcinomas (CCRCC) and in 18% of chromophilic cancers but in no chromophobe cancers or oncocytomas (P=0.016).
Lack of VHL mutations and hypermethylations in chromophobe RCCs and oncocytomas was statistically significant (P = 0.0001 and P = 0.0004, respectively).
Bilateral multiple renal oncocytomas and cysts associated with a constitutional translocation (8;9)(q24.1;q34.3) and a rare constitutional VHL missense substitution.
Mutations in exon 2 of the VHL gene were detected in all three of the sporadic RCCs but were not observed in the matched normal renal tissues or in the two oncocytomas tested.