Fumarate hydratase deficient renal cell carcinoma and fumarate hydratase deficient-like renal cell carcinoma: Morphologic comparative study of 23 genetically tested cases.

Hereditary leiomyomatosis and renal cell carcinoma-associated renal cell carcinoma (HLRCC)/ fumarate hydratase deficient renal cell carcinoma (FHRCC) is an aggressive tumor defined by molecular genetic changes - alteration in fumarate hydratase (FH) gene. The morphologic spectrum of HLRCC/FHDRCC is remarkably variable. The presence of large nuclei and prominent dark red inclusion-like nucleoli and perinucleolar clearing are considered as helpful morphologic clue. We selected 23 renal neoplasms primarily based on their morphologic features suspicious for HLRCC/FHDRCC. Morphological, basic immunohistochemical, and genetic analysis was performed. The tumors were divided in two groups according to the molecular genetic findings. The first group included 13 tumors with detected FH mutation/LOH (compatible with diagnosis FHRCC), and the second group included 10 tumors without FH mutation/LOH (FH-like RCCs). In the FHRCC group, the vast majority of cases (9/13) had mixed morphology with different architectural growth patterns. All cases showed prominent macronucleoli, and perinucleolar clearing was found in 10/13 cases. Immunohistochemically, 6/7 FHRCC cases were negative for FH antibody, while one case showed strong diffuse FH reactivity. The FH-like RCC group showed more uniform architectural growth pattern. All 10 tumors had prominent macronucleoli, and perinucleolar clearing was present in 8/10 cases. Eight FH-like RCC cases showed diffuse strong positivity for FH, although 2 cases were completely negative for FH. It is evident that neither morphologic feature nor immunohistochemical analysis can be reliably used in routine practice for the diagnosis of HLRCC/FHRCC. In suspected cases, the diagnosis of HLRCC/FHRCC can be confirmed by molecular-genetic testing for FH mutation. It should be noted that the traditionally described morphologic features of HLRCC/FHRCC (prominent eosinophilic macronuclei with perinucleolar halos) can frequently be seen in other renal neoplasms.

Morphological, immunohistochemical, and chromosomal analysis of multicystic chromophobe renal cell carcinoma, an architecturally unusual challenging variant.

Chromophobe renal cell carcinoma (ChRCC) is typically composed of large leaf-like cells and smaller eosinophilic cells arranged in a solid-alveolar pattern. Eosinophilic, adenomatoid/pigmented, or neuroendocrine variants have also been described. We collected 10 cases of ChRCC with a distinct multicystic pattern out of 733 ChRCCs from our registry, and subsequently analyzed these by morphology, immunohistochemistry, and array comparative genomic hybridization. Of the 10 patients, 6 were males with an age range of 50-89 years (mean 68, median 69). Tumor size ranged between 1.2 and 20 cm (mean 5.32, median 3). Clinical follow-up was available for seven patients, ranging 1-19 years (mean 7.2, median 2.5). No aggressive behavior was documented. We observed two growth patterns, which were similar in all tumors: (1) variable-sized cysts, resembling multilocular cystic neoplasm of low malignant potential and (2) compressed cystic and tubular pattern with slit-like spaces. Raisinoid nuclei were consistently present while necrosis was absent in all cases. Half of the cases showed eosinophilic/oncocytic cytology, deposits of pigment (lipochrome) and microcalcifications. The other half was composed of pale or mixed cell populations. Immunostains for epithelial membrane antigen (EMA), CK7, OSCAR, CD117, parvalbumin, MIA, and Pax 8 were positive in all tumors while negative for vimentin, TFE3, CANH 9, HMB45, cathepsin K, and AMACR. Ki67 immunostain was positive in up to 1 % of neoplastic cells. Molecular genetic examination revealed multiple chromosomal losses in two fifths analyzable tumors, while three cases showed no chromosomal numerical aberrations. ChRCC are rarely arranged in a prominent multicystic pattern, which is probably an extreme form of the microcystic adenomatoid pigmented variant of ChRCC. The spectrum of tumors entering the differential diagnosis of ChRCC is quite different from that of conventional ChRCC. The immunophenotype of ChRCC is identical with that of conventional ChRCC. Chromosomal numerical aberration pattern was variable; no chromosomal numerical aberrations were found in three cases. All the cases in this series have shown an indolent and non-aggressive behavior.