[1045] "Hybrid Oncocytic/Chromophe Renal Cell Tumours" Do Not Display Genomic Features of Chromophobe Carcinomas

Annick Vieillefond, Nicolas Pote, Florence Mege-Lechevallier, Mathilde Sibony, Philippe Camparo, Vincent Molinie, Jerome Couturier. Hopital Cochin, Paris, France; Hopital Edouard Herriot, Lyon, France; Curie Institute, Paris, France; Hopital Foch, Suresnes, France; Hopital Saint-Joseph, Paris, France

Background: “Hybrid” oncocytic/chromophobe tumours (HOCT) of the kidney are rare tumours of uncertain diagnosis and prognosis, presenting with histological characteristics of both renal oncocytoma (RO), and chromophobe renal-cell carcinoma (ChRCC). Various terminology have been used in the literature: "atypical oncocytoma", “oncocytoma with chromophobe areas”, “tumours with overlapping histology” but the real frequency of HOCT is not known. Based on morphology, and immunohistochemistry, pathologists consider a morphologic spectrum with RO and ChRCC at its ends, and HOCT in between. Based on genomic and cytogenetic datas, RO and ChRCC are two distinct genetic entities, but HOCT were never studied.
The aim of our study is to determine the genomic profile of so-called HOCT using array-CGH.
Design: A series of 42 kidney tumours of the RO/ChRCC group was selected. 30 RO and ChRCC were easily diagnosed and 12 tumours were diagnosed as "HOCT" (2 in BHD patients). HOCT were defined as tumours with admixture of oncocytes and chromophobe cells or with cells with “hybrid” morphology. Colloidal iron and CK7 stainings were analyzed.
For Array-CGH, DNA extraction was done from frozen tumoral samples. Cases were analysed either on a 5K BAC/PAC DNA microarray or on 4x72K NimbleGenR arrays. Genome profiles were visualised using the SignalMapR software (NimbleGenR).
Results: In the majoriry of HOCT tumours, Hale (colloidal iron) staining, displayed an apical positivity, in 80 to 100% of cells, all sporadic tumours except in the two BHD patients. In sporadic tumours, 10% to 100% of cells were CK7-positive, 5 cases contain more than 80% of CK7-positive cells. In BHD tumours, a mosaic pattern was observed.
Array-CGH profiles: in 5 sporadic HOCT as well as in the two BHD cases, no chromosome imbalances were observed. One case showed only a gain of chromosome 18. The 4 other cases showed a small number of chromosome imbalances always involving a loss of 1p or of the whole chromosome 1. No characteristic combined losses of ChRCC were seen.
Conclusions: HOCT display hybrid morphologicy, histochemical and immunohistochemical profiles and a good clinical outcome. Genomic features of so called HOCT show no link with ChRCC. In case of difficult histological diagnosis in the RO/ChRCC group, genome profiling is recommended to exclude a true ChRCC.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 163, Tuesday Morning

 

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