Alpha-methyl CoA racemase (AMACR) reactivity across the spectrum of clear cell renal cell neoplasms.

a-Methylacyl coenzyme A racemase (AMACR) is traditionally considered to be a marker of papillary renal cell carcinoma. However, AMACR expression can be seen in other renal tumors. The aim of this study was to investigate AMACR immunoreactivity within the spectrum of clear cell renal cell neoplasms. Fifty-three clear cell renal epithelial tumors were used in assembling the following four cohorts: low grade (LG) clear cell renal cell carcinoma (CCRCC), high grade (HG) CCRCC, CCRCC with cystic changes, and multilocular cystic renal neoplasm of low malignant potential (MCRNLMP). Representative blocks were stained for AMACR, using two different clones (SP52 and OV-TL12/30). There were at least some AMACR immunoreactivity in 77.8 % and 68.9 % of CCRCCs (using SP52 and OV-TL12/30 clone, respectively). Moderate to strong positivity, or positivity in more than one third of the tumor (even weak in intensity) was detected in 46.7 % of CCRCCs using SP52 and in 48.9 % of CCRCC using OV-TL12/30 clone. The highest AMACR reactivity was observed in HG CCRCC (60 % by SP52 and 66.7 % by OV-TL12/30). Strong and diffuse AMACR positivity was detected in 8.9 % of all CCRCCs. AMACR immunoreactivity in MCRNLMP was 37.5 % (SP52 clone) and 25 % (OV-TL12/30 clone). We demonstrated relatively high expression rate of AMACR in CCRCC, while very variable in intensity and distribution. This finding may have diagnostic implications especially in limited samples (i.e., core biopsies), as AMACR positivity does not exclude the diagnosis of CCRCC.

A large-scale assay library for targeted protein quantification in renal cell carcinoma tissues.

Renal cell carcinoma (RCC) represents 2.2% of all cancer incidences; however, prognostic or predictive RCC biomarkers at protein level are largely missing. To support proteomics research of localized and metastatic RCC, we introduce a new library of targeted mass spectrometry assays for accurate protein quantification in malignant and normal kidney tissue. Aliquots of 86 initially localized RCC, 75 metastatic RCC and 17 adjacent non-cancerous fresh frozen tissue lysates were trypsin digested, pooled, and fractionated using hydrophilic chromatography. The fractions were analyzed using LC-MS/MS on QExactive HF-X mass spectrometer in data-dependent acquisition (DDA) mode. A resulting spectral library contains 77,817 peptides representing 7960 protein groups (FDR = 1%). Further, we confirm applicability of this library on four RCC datasets measured in data-independent acquisition (DIA) mode, demonstrating a specific quantification of a substantially increased part of RCC proteome, depending on LC-MS/MS instrumentation. Impact of sample specificity of the library on the results of targeted DIA data extraction was demonstrated by parallel analyses of two datasets by two pan human libraries. The new RCC specific library has potential to contribute to better understanding the RCC development at molecular level, leading to new diagnostic and therapeutic targets.

Eosinophilic vacuolated tumor (EVT) of kidney demonstrates sporadic TSC/MTOR mutations: next-generation sequencing multi-institutional study of 19 cases.

A distinct renal tumor has recently been described as "high-grade oncocytic renal tumor" and "sporadic renal cell carcinoma with eosinophilic and vacuolated cytoplasm". The Genitourinary Pathology Society (GUPS) consensus proposed a unifying name "eosinophilic vacuolated tumor" (EVT) for this emerging entity. In this multi-institutional study, we evaluated 19 EVTs, particularly their molecular features and mutation profile, using next-generation sequencing. All cases were sporadic and none of the patients had a tuberous sclerosis complex. There were 8 men and 11 women, with a mean age of 47 years (median 50; range 15-72 years). Average tumor size was 4.3 cm (median 3.8 cm; range 1.5-11.5 cm). All patients with available follow-up data (18/19) were alive and without evidence of disease recurrence or progression during the follow-up, ranging from 12 to 198 months (mean 56.3, median 41.5 months). The tumors were well circumscribed, but lacked a well-formed capsule, had nested to solid growth, focal tubular architecture, and showed ubiquitous, large intracytoplasmic vacuoles, round to oval nuclei, and prominent nucleoli. Immunohistochemically, cathepsin K, CD117, CD10, and antimitochondrial antigen were expressed in all cases. Other positive stains included: PAX8, AE1/AE3 and CK18. CK7 was typically restricted only to rare scattered cells. Vimentin, HMB45, melan-A, and TFE3 were negative in all cases. All tumors showed retained SDHB. All cases (19/19) showed non-overlapping mutations of the mTOR pathway genes: TSC1 (4), TSC2 (7), and MTOR (8); one case with MTOR mutation showed a coexistent RICTOR missense mutation. Low mutational rates were found in all samples (ranged from 0 to 6 mutations/Mbp). Microsatellite instability and copy number variations were not found in any of the 17 analyzable cases. EVT represents an emerging renal entity that shows a characteristic and readily identifiable morphology, consistent immunohistochemical profile, indolent behavior, and mutations in either TSC1, TSC2, or MTOR genes.

Clear cell renal cell carcinoma with prominent microvascular hyperplasia: Morphologic, immunohistochemical and molecular-genetic analysis of 7 sporadic cases.

Clear cell renal cell carcinoma (CCRCC) is well known for intratumor heterogeneity. An accurate mapping of the tumor is crucial for assessing prognosis, and perhaps this can be linked to potential success/failure of targeted therapies. We assembled a cohort of 7 CCRCCs with prominent vasculature and microvascular hyperplasia (ccRCCPV), resembling those seen in high grade gliomas. A control group of classic CCRCC with no variant morphologies was also included. Both groups were analyzed for clinicopathologic, morphologic, immunohistochemical, and molecular genetic features. No statistically significant differences in mRNA expression of studied genes between the two groups were found. Using NGS panel Trusight Oncology 500 (TSO500), only one clinically significant gene mutation, VHL c.263G > A, p. (Trp88Ter), was found. TMB (Tumor Mutation Burden) and MSI (MicroSatellite Instability) were low, and no copy number variations (CNVs) were detected in the study cohort. Prominent microvascular hyperplasia in CCRCC is a rare phenomenon. From molecular genetic point of view, these tumors do not appear to be different from classic CCRCC. Prognostically, they also demonstrated similar clinical behaviors.

Histologic diversity in chromophobe renal cell carcinoma does not impact survival outcome: A comparative international multi-institutional study.

Predicting the clinical behavior and trajectory of chromophobe renal cell carcinoma (ChRCC) by histologic features has so far proven to be challenging. It is known that ChRCC represents a heterogeneous group of neoplasms demonstrating variable, yet distinctive morphologic and genetic profiles. In this international multi-institutional study, we aimed to assess the impact of histologic diversity in ChRCC (classic/eosinophilic versus rare subtypes) on survival outcome. This is an international multi-institutional matched case-control study including 14 institutions, examining the impact of histologic subtypes of ChRCC on survival outcome. The study group (cases) included 89 rare subtypes of ChRCC. The control group consisted of 70 cases of ChRCC including classic and eosinophilic features, age- and tumor size-matched. Most of the rare subtypes were adenomatoid cystic/pigmented ChRCC (66/89, 74.2%), followed by multicystic ChRCC (10/89, 11.2%), and papillary ChRCC (9/89, 10.1%). In the control group, there were 62 (88.6%) classic and 8 (11.4%) eosinophilic ChRCC. There were no statistically significant differences between the study and control groups for age at diagnosis, gender distribution, tumor size, presence of tumor necrosis, presence of sarcomatoid differentiation, and adverse outcomes. No statistically significant differences were found in clinical outcome between the rare subtypes and classic/eosinophilic groups by tumor size, necrosis, and sarcomatoid differentiation. Further, no statistically significant differences were found in clinical outcome between the two groups, stratified by tumor size, necrosis, and sarcomatoid differentiation. Our findings corroborated previous studies that both sarcomatoid differentiation and tumor necrosis were significantly associated with poor clinical outcome in classic/eosinophilic ChRCC, and this was proven to be true for ChRCC with rare histologic subtypes as well. This study suggests that rare morphologic patterns in ChRCC without other aggressive features play no role in determining the clinical behavior of the tumor.

Renal cell carcinomas with tubulopapillary architecture and oncocytic cells: Molecular analysis of 39 difficult tumors to classify.

So-called oncocytic papillary renal cell carcinoma (OPRCC) is a poorly defined variant of papillary renal cell carcinoma. Since its first description, several studies were published with conflicting results, and thus precise definition is lacking. A cohort of 39 PRCCs composed of oncocytic cells were analyzed. Cases were divided into 3 groups based on copy number variation (CNV) pattern. The first group consisted of 23 cases with CNV equal to renal oncocytoma. The second group consisted of 7 cases with polysomy of chromosomes 7 and 17 and the last group of 9 cases included those with variable CNV. Epidemiologic, morphologic and immunohistochemical features varied among the groups. There were not any particular histomorphologic features correlating with any of the genetic subgroups. Further, a combination of morphologic, immunohistochemical, and molecular-genetic features did not allow to precisely predict biologic behavior. Owing to variable CNV pattern in OPRCC, strict adherence to morphology and immunohistochemical profile is recommended, particularly in limited samples (i.e., core biopsy). Applying CNV pattern as a part of a diagnostic algorithm can be potentially misleading. OPRCC is a highly variable group of tumors, which might be misdiagnosed as renal oncocytoma. Using the term OPRCC as a distinct diagnostic entity is, thanks to its high heterogeneity, questionable.

Molecular Genetic Features of Primary Nonurachal Enteric-type Adenocarcinoma, Urachal Adenocarcinoma, Mucinous Adenocarcinoma, and Intestinal Metaplasia/Adenoma: Review of the Literature and Next-generation Sequencing Study.

The diagnosis of primary adenocarcinoma of the urinary bladder may be challenging in routine practice. These tumors may morphologically and immunohistochemically overlap with urachal adenocarcinoma and colorectal adenocarcinoma. Further, their genetic background is poorly understood. We systematically searched the PubMed database for results of complex genetic evaluation of primary bladder adenocarcinoma subtypes. Subsequently, we designed our own series of bladder lesions. We evaluated 36 cases: 16 primary enteric-type adenocarcinomas, 7 urachal enteric adenocarcinomas, 3 primary mucinous/colloid adenocarcinomas, and 10 intestinal-type metaplasia/villous adenoma. Detailed clinical data were collected, and all cases were examined using targeted next-generation sequencing. On the basis of the literature, the first mutated gene in these tumors was reported to be KRAS in 11.3% of cases, followed by TERT promoter mutations in 28.5%. In addition to KRAS and TERT, other genes were also found to be frequently mutated in primary bladder adenocarcinoma, including TP53, PIK3CA, CTNNB1, APC, FBXW7, IDH2, and RB1. In our series, the most frequent gene mutations in primary enteric-type adenocarcinomas were as follows: TP53 (56%); BRCA2, KMT2B (both 33%); NOTCH2, KDR, ARID1B, POLE, PTEN, KRAS (all 28%); in urachal enteric adenocarcinoma they were as follows: TP53 (86%); PTEN, NOTCH (both 43%); in primary mucinous/colloid adenocarcinomas they were as follows: KRAS, GRIN2A, AURKB (all 67%); and, in intestinal-type metaplasia/villous adenoma, they were as follows: APC, PRKDC (both 60%); ROS1, ATM, KMT2D (all 50%). No specific mutational pattern was identified using cluster analysis for any of the groups. Herein, we describe the pathologic features and immunohistochemical staining patterns traditionally used in the differential diagnoses of glandular lesions of the bladder in routine surgical pathology. We outline the mutational landscape of these lesions as an aggregate of published data with additional data from our cohort. Although diagnostically not discriminatory, we document that the most common genetic alterations shared between these glandular neoplasms include TP53, APC (in the Wnt pathway), and KRAS (in the MAPK pathway) mutations.

Utility of NKX3.1 immunohistochemistry in the differential diagnosis of seminal vesicles versus prostatic tissue in needle biopsy.

NKX3.1 is considered a reliable immunohistochemical marker of prostatic origin with high specificity and sensitivity. However, NKX3.1 positivity has been described in other neoplastic and non-neoplastic tissues, such as mesenchymal chondrosarcoma, sex-cord stromal tumors, rete testis adenocarcinoma, lobular and ductal carcinoma of the breast, salivary glands, peribronchial submucosal glands, and Sertoli cells. We analyzed expression of two antibodies (mono and polyclonal) of NKX3.1 in a total of 63 non-neoplastic seminal vesicles. We used 52 resection materials (12 seminal vesicles without prostatic adenocarcinoma, 26 seminal vesicles with prostatic adenocarcinoma infiltration, and 14 cases of seminal vesicles infiltrated by urothelial carcinoma) and 11 prostatic core needle biopsies with incidentally sampled fragment of seminal vesicles. In all cases, tissues from seminal vesicles were completely negative for NKX3.1, despite using polyclonal and monoclonal NKX3.1 antibodies, and regardless of the detection system utilized (diaminobenzidine (DAB) versus alkaline phosphatase (AF)). However, prostatic adenocarcinoma was negative in several cases (n = 6), when AF detection system was used. Reaction with DAB was strong and robust in all cases. Based on our data, we can recommend NKX3.1 as a negative immunohistochemical marker of seminal vesicles.

Papillary renal cell carcinoma with prominent spindle cell stroma - tumor mimicking mixed epithelial and stromal tumor of the kidney: Clinicopathologic, morphologic, immunohistochemical and molecular genetic analysis of 6 cases.

Papillary renal cell carcinoma (PRCC) is currently a well-studied type of RCC. In addition to PRCC type 1, there are a number of other subtypes and variants of PRCCs which have been reported. We describe a series of 6 PRCCs with papillary, micropapillary and/or tubulopapillary architecture and prominent spindle cell stroma, resembling stroma in mixed epithelial and stromal tumor of the kidney (MESTK) or sarcomatoid RCC. Clinicopathologic, morphologic, immunohistochemical and molecular features were analyzed. All patients were males with an age range of 44-98 years (mean 65.3, median 65.5 years). Tumor size ranged from 2.4-11.4 cm (mean 5.8, median 4.5 cm). Follow-up data were available for 4 patients, ranging from 3 to 96 months (mean 42.75, median 36 months). Epithelial cells were mostly cylindrical with eosinophilic cytoplasm, showing nuclear grade 2 and 3 (ISUP/WHO). In all cases, loose to compact prominent stroma composed of spindle cells, without malignant mesenchymal heterologous elements was detected. No atypical mitoses were found, while typical mitoses were rare in both epithelial and stromal components. Epithelial cells were positive for CK7, AMACR, and vimentin in all cases, while negative for TFE3, HMB45, desmin, CD34, and actin. The stroma was positive for vimentin, actin and focally for CD34, while negative for CK7, AMACR, TFE3, HMB45, and desmin. Estrogen and progesterone receptors were completely negative. FH and SDHB expression was retained in all analyzable cases. Proliferative index was barely detectable in stromal component and low in epithelial component, ranging 0 to 5% positive stained cells/high power field. Copy number variation was variable with no distinct pattern. No mutations in CDKN2A, BAP1, MET were detected. PRCC with MESTK-like features is a distinct variant of PRCC mimicking MESTK. Our findings add to the body of literature on ever expanding variants of PRCCs. Both epithelial and stromal components lacked true Müllerian features, which was also proven by immunohistochemistry.

Practices recommendations in the applications of immunohistochemistry and molecular genetics in testicular tumors. Review article.

The great majority of testicular tumors can be diagnosed on the basis of morphology, while immunohistochemistry and molecular genetics assist in only a small proportion of cases. Similar to other areas of pathology, ancillary diagnostic methods have to be used responsibly and assessed in correlation with morphological, serological and clinical findings. Prior to their effective use, a limited differential diagnosis based on morphology is required.The significance of germ cell tumors is underscored by the fact that they represent the most frequent solid neoplasms occurring in men between 20-30 years and if diagnosed correctly and in early stage, they have excellent prognosis. From the molecular genetic standpoint, germ cell tumors stand apart from the current trend of tumor stratification based on molecular profiles. It is mainly due to the low mutational load, since the main genetic abnormality are chromosomal aneuploidies. Given the frequency of germ cell tumors among testicular neoplasms and since morphology is usually diagnostically most valuable, this review article is focused mainly on germ cell tumors, emphasizing the morphological features. Sertoli cell tumor, NOS is the only sex-cord stromal tumor included in this review as its diagnosis can be challenging. For practical purposes, this reviewis focused on differential diagnosis, including only entities where misdiagnosis would have impact on clinical outcome.

Reactivity of CK7 across the spectrum of renal cell carcinomas with clear cells.

AIMS: Current available data on cytokeratin 7 (CK7) immunostaining pattern in the clear cell renal cell carcinoma (RCC) spectrum is conflicting. The aim of this study was to assess CK7 immunoreactivity within the spectrum of clear cell renal neoplasms, including clear cell RCC, multicystic renal neoplasm of low malignant potential and clear cell papillary RCC-like tumours. METHODS AND RESULTS: We analysed two clones of CK7 and two tumour blocks for a total of 75 cases divided into five distinct groups: (i) low-grade clear cell RCC, (ii) high-grade clear cell RCC, (iii) multicystic renal neoplasm of low malignant potential, (iv) clear cell RCC with cystic changes and (v) clear cell papillary RCC-like tumours. We found the highest CK7 reactivity in low-grade clear cell RCC, multicystic renal neoplasm of low malignant potential and clear cell papillary RCC-like groups, ranging from 60% to 93%. CONCLUSIONS: Our findings show that CK7 immunoreactivity in clear cell RCC is variable, and the extent of staining depends on the grade and architectural growth patterns of the tumours.

Primary renal well-differentiated neuroendocrine tumour (carcinoid): next-generation sequencing study of 11 cases.

AIMS: Primary renal well-differentiated neuroendocrine tumour (NET) (hereafter referred to as renal NET) is rare, with ~100 cases having been reported in the literature. There are also limited data on the molecular-genetic background of primary renal NETs. METHODS AND RESULTS: We analysed 11 renal NETs by using next-generation sequencing (NGS) to identify characteristic genetic aberrations. All tumours were positive for synaptophysin, and also expressed insulinoma-associated protein 1 (10/11), chromogranin-A (8/11), and CD56 (3/11). Cytoplasmic positivity of CD99 was present in eight of 11 cases, and strong nuclear expression of α-thalassaemia/mental retardation syndrome X-linked (ATRX) was retained in all 11 cases. Molecular-genetic analysis of aberration of VHL gave negative results in all cases. Loss of heterozygosity on chromosome 3p21 was found in three of nine analysable cases. NGS was successful in nine cases, showing a total of 56 variants being left after the updated filtering process, representing an average of five variants per sample. All analysable cases were negative for ATRX and DAXX (death-domain associated protein X) mutations. The most frequently mutated genes were CDH1 and TET2, with three mutations in two cases. Mutations in AKT3, ROS1, PIK3R2, BCR and MYC were found in two cases. The remaining 41 genes were found to be mutated only in individual cases. In four cases, the mutations affected a subset of genes related to angiogenesis. CONCLUSIONS: Overall, the mutation profile of primary renal NETs is variable, and none of the studied genes or affected pathways seems to be specific for renal NET.

Outcomes for Patients after Resection of Pulmonary Metastases from Clear Cell Renal Cell Carcinoma: 18 Years of Experience.

INTRODUCTION: Clear cell renal cell carcinoma (ccRCC) is the most common kidney tumor. If feasible, metastasectomy is preferably indicated in metastatic disease. OBJECTIVE: The aim of this study was to determine the outcome of patients after pulmonary metastasectomy (PM). METHODS: PM for ccRCC was performed in 35 patients in the period of January 2001-2019. Clinical characteristics, type of surgery, histopathology results, and follow-up data were recorded. Progression-free survival (PFS) after PM and overall survival (OS) were defined as outcome endpoints. RESULTS: A total of 77 PMs were performed in 35 patients after nephrectomy for ccRCC. The mean size of pulmonary metastasis was 19.0 mm (4-90). With a median follow-up after PM of 79.2 months, the 3- and 5-year OS rates were 63.5 and 44.9%, respectively. The only statistically significant prognostic factor affecting both PFS (p = 0.019) and OS (p = 0.015) was the dimension of pulmonary metastases. CONCLUSIONS: The prognosis of metastatic ccRCC is generally poor, particularly in cases of larger size of metastasis. PM might improve the individual prognosis of patients with lung metastasis even in cases with higher number of metastases, bilaterality, synchronous metastasis, or a short progression-free interval after nephrectomy.

Papillary pattern in clear cell renal cell carcinoma: Clinicopathologic, morphologic, immunohistochemical and molecular genetic analysis of 23 cases.

Clear cell renal cell carcinoma (ccRCC), the most common histologic subtype of RCCs, demonstrates a wide spectrum of morphologic features (i.e., low-grade spindle cell, syncytial giant cells, and mucin-producing cells). However, papillary growth pattern in ccRCCs is rather a rare finding, which can present challenges in differential diagnostic work up. The aim of this study was to investigate ccRCCs with predominant papillary features from morphologic, immunohistochemical and molecular genetic perspectives. 23 clear cell renal cell carcinomas with papillary architecture were selected. Tumors were evaluated morphologically, immunohistochemically, and molecularly by next-generation sequencing (NGS). The diagnosis of MiT family translocation RCC was excluded by TFE3 immunohistochemistry. Mean age of patients was 65.2 years (range 42-81 years), and 19/23 were male. Tumor size ranged from 1.6 to 12.8 cm (median 6.5 cm). At a median follow-up of 2.5 years (range 1.5-9 years), 2 patients (8.7%) died of disease, 2 developed metastasis. Areas of papillary pattern accounted for approximately 40-100% of the tumor. CK7 was negative in non-papillary areas in majority of cases (20/23, 87%), and was only focally positive in 3/23 cases (13%). In papillary areas, AMACR was positive/focally positive in 17/23 (73.9%) cases and in the non-papillary areas it was positive/focally positive in 22/23 (95.6%) cases. CAIX was mainly negative in both non-papillary and papillary areas (15/23 [65%] and 16/23 [69.5%], respectively). Molecular analysis of 15 analyzable cases revealed the most frequently mutated gene to be VHL (in 9 cases), followed by PRBM1 (in 2 cases) and 29 other different mutations in various genes. Papillary growth pattern in ccRCC is not an uncommon situation. Papillary RCC with clear cells and MiT family (TFE3) translocation RCCs are the major differential diagnostic considerations in such scenarios. Our NGS molecular analysis supported classifying such tumors as a morphologic variant of ccRCC.

Clear cell renal cell carcinoma with Paneth-like cells: Clinicopathologic, morphologic, immunohistochemical, ultrastructural, and molecular analysis of 13 cases.

Clear cell renal cell carcinoma (CRCC) is well known for its intratumoral heterogeneity. Paneth-like cells (PLC) have been reported in variable organs (i.e., hepatobiliary, genitourinary, and female genital tract). In genitourinary system, it is possible to find PLCs in epididymis, urinary bladder and prostate. The objective of this study was to assess PLC in CRCCs 13 CRCCs with prominent PLC (CRCCPLC) were selected out of 1378 CRCCs in our registry. The tumors were analyzed using morphologic, immunohistochemical, ultrastructural, and molecular genetic methods. CRCCPLCs were mostly of low histologic grade (12/13). Immunohistochemical profile was compatible with classic CRCC. PLC constituted 10 to-70% of the tumor volume (mean 17.7%, median 10%). PLCs did not express neuroendocrine markers (chromogranin, synaptophysin, CD56, INSM-1). Ultrastructurally, PLCs were filled by membrane bounded vesicles of various sizes and were compatible with secretory type of cells. VHL mutation was found in 9/9 cases, and LOH3p was found in 6/8 analyzable cases. Conclusions: PLC morphology can variably be present in "classic" CRCC, even in a substantial proportion. Ultrastructurally, PLCs have all attributes of secretory cells. Preliminary follow up data showed that these tumors may not be associated with aggressive clinical behavior.

Fumarate hydratase deficient renal cell carcinoma: Chromosomal numerical aberration analysis of 12 cases.

Hereditary leiomyomatosis and renal cell carcinoma-associated renal cell carcinoma (HLRCC)/fumarate hydratase deficient renal cell carcinoma (FHRCC) is defined by molecular genetic changes (mutation/LOH in fumarate hydratase (FH) gene). We investigated chromosomal numerical aberration pattern (CNV) in FHRCC/HLRCC using array comparative genomic hybridization analysis and low pass whole genome sequencing. Genetic analysis was successfully completed in 12 tumors. Most common chromosomal aberrations detected were a complete or partial loss of chromosome 4 (5/12 cases), chromosome 15 (4/12 cases), and chromosomes 9, 13, and 14 (each in 3/12 cases), as well as a complete or partial gain of chromosome 17 (in 4/12 cases). No chromosomal losses or gains were detected in 4 cases. Copy number variation pattern in FHRCC/HLRCC appears to be highly variable and does not provide a useful diagnostic tool in identifying these cases. Immunohistochemical staining and especially molecular genetic evaluation of FH gene mutations/LOH remain the gold standard in identifying FHRCC/HLRCC.

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.

Low-grade spindle cell proliferation in clear cell renal cell carcinoma is unlikely to be an initial step in sarcomatoid differentiation.

AIMS: Spindle cell proliferation within clear cell renal cell carcinoma (ccRCC) is usually considered as a sarcomatoid differentiation. Low-grade spindle cell proliferation (LG-SCP) in ccRCC was first described in 2001. This phenomenon is not common and can pose diagnostic challenges, particularly in core biopsies. The aim of this study was to describe morphological, immunohistochemical and molecular characteristics of ccRCCs with LG-SCP. METHODS AND RESULTS: Eleven cases of ccRCC with LG-SCP were retrieved from approximately 21 000 renal tumours in our registry. Ten cases of conventional ccRCC and 10 cases of typical sarcomatoid ccRCC were included as control groups. Morphological and immunohistochemical characteristics of epithelial-mesenchymal transition (EMT) were analysed. Von Hippel-Lindau syndrome gene abnormalities were also analysed using molecular genetics. Among ccRCC with LG-SCP cases, there were five males and five females (clinical information was not available in one case) with a median age of 67 years (mean: 68.5, range: 60-81 years). Average tumour size was 7.1 cm (median:7.5, range:1.7-12 cm). Follow-up data were available in nine cases (mean: 44.78 months), with no aggressive behaviour seen. On average, LG-SCP areas constituted 5-80% of tumour volume (mean: 32.3%). Necrotic/regressed areas were seen in all cases ranging from 5% to 30%. LG-SCP was clearly epithelial, with no mitoses or any evidence of mesenchymal differentiation. Immunohistochemical profile of LG-SCP was consistent with 'conventional' ccRCC. Compared with sarcomatoid ccRCC, some EMT markers showed alteration in LG-SCP, including lower expression of N-cadherin and Zeb1 as well as higher expression of E-cadherin. However, there were no significant differences in EMT markers between LG-SCP and conventional ccRCC. Abnormalities in VHL (mutations, LOH3p) were found in six of 11 cases. CONCLUSIONS: Our findings showed that LG-SCP in ccRCC have comparable immunohistochemical and molecular characteristics to those seen in 'conventional' ccRCC. Further, immunohistochemical analysis of EMT markers showed that LG-SCP did not differ from 'conventional' ccRCC. We believe that LG-SCP is a part of morphological heterogeneity in ccRCCs and that they may not represent an initial stage of sarcomatoid differentiation. This is supported further by the fact that ccRCC with LG-SCP did not display more aggressive behaviour than 'conventional' ccRCC.

Magnetic resonance imaging as an adjunct diagnostic tool in computed tomography defined Bosniak IIF-III renal cysts: a multicenter study.

INTRODUCTION: CT imaging is the standard examination for renal cystic lesions and defines the Bosniak category, which dictates further management. Given that Bosniak II/IIF/III renal cystic lesions can potentially harbor renal cell carcinoma (RCC), additional diagnostic modalities may be required in management decision making. AIM: To determine the value of additional magnetic resonance imaging in CT-defined Bosniak IIF-III renal cystic lesions. MATERIALS AND METHODS: This a multicenter retrospective study of 46 consecutive patients, diagnosed with cystic renal lesions between 2009 and 2016. The inclusion criteria were: (1) cystic renal lesion classified as Bosniak IIF-III on CT, (2) a subsequent MRI examination, and (3) documented outcome via surgery for cystic renal mass or follow-up. RESULTS: 46 patients (35 males, 11 females) were included. The mean size of the cystic lesion was 3.92 cm (0.7-10 cm). According to the CT findings, Bosniak IIF and III were found in 12 (26.1%) and 34 (73.9%) cases. Reclassification of Bosniak category was done after MRI examination in 31 cases (67.4%). An upgrade rate of 58.7% (27 cases) to a higher category was made, while the downgrade rate to a lower category was achieved in 4 cases (8.7%). As a result, significant therapeutic management change was made in 12/31 patients (38.7%), of whom 8 underwent subsequent surgery. CONCLUSION: MRI study may reduce the use of Bosniak IIF category (in comparison with CT), which has a direct impact on therapeutic management (surgery vs. surveillance) in a significant proportion of patients.

Cystic Appearance on Imaging Methods (Bosniak III-IV) in Histologically Confirmed Papillary Renal Cell Carcinoma is Mainly Characteristic of Papillary Renal Cell Carcinoma Type 1 and Might Predict a Relatively Indolent Behavior of Papillary Renal Cell Carcinoma.

AIM: The aim of this study was to determine the proportion of cystic tumors according to preoperative CT (Bosniak III, IV) among surgically treated patients with histologically confirmed papillary renal cell carcinoma (pRCC) and to assess progression rates among patients with and without cystic appearance on imaging. METHODS: A total of 138 patients with pRCC histology surgically treated in the period of January 2007-March 2017 were included. Clinical and radiological characteristics, type of surgery, histopathology results, and follow-up data were recorded and statistically evaluated. RESULTS: Forty-one cases (29.7%) of cystic lesions (10× BIIF, 14× BIII, 17× BIV) were detected by CT. Patients with pRCC1 significantly more frequently presented with cystic appearance on CT (33/78; 42.3%) in comparison to other papillary types (8/60; 13.3%; p = 0.0002). During a median follow-up time of 49.4 months, only 2 patients with cystic lesions progressed after surgery. CONCLUSIONS: Cystic appearance on imaging methods is mainly a characteristic of pRCC1 (42.3%). Cystic morphology on imaging might predict a relatively indolent behavior of all pRCC types. Preoperative scoring systems including tumor growth patterns (cystic vs. solid) are needed for further classification.