KIT expression in chromophobe renal cell carcinoma: comparative immunohistochemical analysis of KIT expression in different renal cell neoplasms

Characterization of Intercalated Cell Markers KIT and LINC01187 in Chromophobe Renal Cell Carcinoma and Other Renal Neoplasms

Introduction. Chromophobe renal cell carcinoma (chromophobe RCC) is the third major subcategory of renal tumors after clear cell RCC and papillary RCC, accounting for approximately 5% of all RCC subtypes. Other oncocytic neoplasms seen commonly in surgical pathology practice include the eosinophilic variant of chromophobe RCC, renal oncocytoma, and low-grade oncocytic unclassified RCC. Methods. In our recent next-generation sequencing based study, we nominated a lineage-specific novel biomarker LINC01187 (long intergenic non-protein coding RNA 1187) which was found to be enriched in chromophobe RCC. Like KIT (cluster of differentiation 117; CD117), a clinically utilized chromophobe RCC related biomarker, LINC01187 is expressed in intercalated cells of the nephron. In this follow-up study, we performed KIT immunohistochemistry and LINC01187 RNA in situ hybridization (RNA-ISH) on a cohort of chromophobe RCC and other renal neoplasms, characterized the expression patterns, and quantified the expression signals of the two biomarkers in both primary and metastatic settings. Results. LINC01187, in comparison to KIT, exhibits stronger and more uniform expression within tumors while maintaining temporal and spatial consistency. LINC01187 also is devoid of intra-tumoral heterogeneous expression pattern, a phenomenon commonly noted with KIT. Conclusions. LINC01187 expression can augment the currently utilized KIT assay and help facilitate easy microscopic analyses in routine surgical pathology practice.

Primary pulmonary T-cell lymphoma after operation for small intestinal stromal tumor: A case report

Background

The risk of gastrointestinal stromal tumor (GIST) in combination with other primary malignancies is high, which occurs before and after the diagnosis of GIST. Primary pulmonary T-cell lymphoma is a rare type of non-Hodgkin lymphoma.

Case presentation

We report a 53-year-old male patient who was admitted to our hospital with fever, cough, and expectoration for 2 weeks. Chest computed tomography (CT) showed a cavitary mass in the left lower lobe with multiple nodules in the upper lobes of both lungs. The patient had a history of surgery for small intestinal stromal tumors and was treated with oral imatinib after surgery. Lung biopsy was diagnosed as lymphomatoid granulomatosis, tending to grade 3. The pathological diagnosis was corrected by surgery and genetic testing for lung non-Hodgkin CD8-positive cytotoxic T-cell lymphoma with Epstein–Barr virus (EBV) infection in some cells. After multiple chemotherapies, the CT scan showed a better improvement than before. The patient is still under follow-up, and no tumor recurrence has been found.

Conclusion

Patients with a history of GIST should be monitored for other malignancies. The clinical symptoms and imaging examinations of primary pulmonary T-cell lymphoma are not characteristic, and the definite diagnosis still depends on pathological examination. The patient was treated with the CHOP chemotherapy regimen after the operation, the curative effect was good.

NKX6-1 Is a Less Sensitive But Specific Biomarker of Chromophobe Renal Cell Carcinoma

NKX6-1 is a transcription factor that plays a key role in the development, differentiation, and identity maintenance of beta cells of pancreatic islets. Although NKX6-1 expression has also been discovered in pancreatic well-differentiated neuroendocrine tumors (WDNETs) and duodenal WDNETs, its expression in chromophobe renal cell carcinoma (chRCC) is unexplored. Analysis of mRNA expression and immunohistochemistry of NKX6-1 was performed using the kidney cancer cohort from The Cancer Genome Atlas (TCGA) and paraffin-embedded whole-tissue slides from our 196 collected cases, including 48 chRCCs (43 classic and 5 eosinophilic subtypes), 24 renal oncocytomas (ROs), 46 clear cell renal cell carcinomas, 41 papillary renal cell carcinomas, 14 renal urothelial carcinomas, 7 low-grade oncocytic renal tumors (LOTs), 8 eosinophilic solid and cystic renal cell carcinomas, 3 succinate dehydrogenase-deficient renal cell carcinomas, and 5 renal oncocytic tumors, not otherwise specified. NKX6-1 expression was almost exclusively upregulated in chRCC at both the mRNA and protein levels compared with other renal tumors. NKX6-1 was immunohistochemically positive in 39 of 48 (81.3%) chRCCs, but negative in 46 clear cell renal cell carcinomas, 24 ROs, 7 low-grade oncocytic renal tumors, 8 eosinophilic solid and cystic renal cell carcinomas, 3 succinate dehydrogenase-deficient renal cell carcinomas, and 5 renal oncocytic tumors, not otherwise specified. Diffuse, moderate, and focal NKX6-1 staining were seen in 21, 4, and 14 of the 39 chRCCs, respectively. In contrast, NKX6-1 was focally positive in only 1 of 41 (2.4%) papillary renal cell carcinomas and 2 of 14 (14.3%) renal urothelial carcinomas. Therefore, the sensitivity and specificity of NKX6-1 staining were 81.3% and 98% for chRCC, respectively. In conclusion, NKX6-1 may be a novel potential marker for differentiating chRCC from other renal neoplasms, especially from RO.

Chromophobe renal cell carcinoma or oncocytoma: a manner of challenge in frozen section diagnosis

Chromophobe renal cell carcinoma (RCC) is a rare type of kidney neoplasm that is diagnosed in the 6th decade of life with similar incidence in male and female. We reported a case of 73-year-old man with a chief complaint of nocturia, frequency, dribbling and urinary retention with renal mass in ultrasound examination. Histologic examination and immunohistochemistry study revealed the diagnosis of chromophobe RCC which initially was mistaken for oncocytoma in frozen section diagnosis. The pathologist should be aware of this malignant entity and be cautious in diagnosing oncocytoma in frozen section and routine H & E staining.

Clinicopathological characteristics of KIT and protein kinase C-δ expression in adenoid cystic carcinoma: comparison with chromophobe renal cell carcinoma and gastrointestinal stromal tumour

AIMS

KIT overexpression is frequently observed in adenoid cystic carcinomas (AdCCs), chromophobe renal cell carcinomas (ChRCCs), and gastrointestinal stromal tumours (GISTs). Persistent KIT activation has been reported to be mediated by protein kinase C (PKC)-δ in a subset of colon cancers with wild-type KIT overexpression, and by PKC-θ in GISTs with mutant KIT overexpression. To elucidate the clinical implications of PKC-δ and PKC-θ expression in KIT-expressing tumours, we investigated the expression of KIT, PKC-δ and PKC-θ in AdCCs and ChRCCs in comparison with GISTs.

METHODS AND RESULTS

KIT expression, PKC-δ expression and PKC-θ expression were analysed in whole sections from 41 AdCCs, 40 ChRCCs and 56 GISTs by immunohistochemistry. Membranous expression of KIT was found in 34 AdCCs and all ChRCCs, whereas cytoplasmic expression of KIT was found in 46 GISTs. In AdCCs, PKC-δ expression was associated with histological grade (P = 0.049), lymphovascular invasion (P = 0.004), perineural invasion (P = 0.002), and KIT positivity (P = 0.002). PKC-δ positivity was associated with shorter relapse-free survival (RFS) (P = 0.017) and a tendency for there to be shorter overall survival (OS) (P = 0.090) in patients with AdCCs. No clinicopathological associations were observed between PKC-δ and KIT expression in ChRCCs. In GISTs, PKC-θ expression was associated with higher mitotic count (P = 0.011) and high grade according to the modified National Institutes of Health criteria (P < 0.001). PKC-θ positivity was associated with shorter RFS (P = 0.016) and a tendency for there to be shorter OS (P = 0.051) in patients with GISTs.

CONCLUSIONS

PKC-δ expression is associated with KIT expression and the prognosis of patients with AdCCs, suggesting that PKC-δ may be a potential therapeutic target for AdCCs.

Morphologic, Molecular, and Taxonomic Evolution of Renal Cell Carcinoma: A Conceptual Perspective With Emphasis on Updates to the 2016 World Health Organization Classification

Molecular and morphologic interrogation has driven a much-needed reexamination of renal cell carcinoma (RCC). Indeed, the recently released 2016 World Health Organization classification now recognizes 12 distinct RCC subtypes, as well as several other emerging/provisional RCC entities. From a clinical perspective, accurate RCC classification may have important implications for patients and their families, including prognostic risk stratification, targeted therapeutics selection, and identification for genetic testing. In this review, we provide a conceptual framework for approaching RCC diagnosis and classification by categorizing RCCs as tumors with clear cytoplasm, papillary architecture, and eosinophilic (oncocytic) cytoplasm. The currently recognized 2016 World Health Organization classification for RCC subtypes is briefly discussed, including new diagnostic entities (clear cell papillary RCC, hereditary leiomyomatosis and RCC-associated RCC, succinate dehydrogenase-deficient RCC, tubulocystic RCC, and acquired cystic disease-associated RCC) and areas of evolving RCC classification, such as transcription elongation factor B subunit 1 (TCEB1)-mutated RCC/RCC with angioleiomyoma-like stroma/RCC with leiomyomatous stroma, RCC associated with anaplastic lymphoma receptor tyrosine kinase (ALK) gene rearrangement, thyroidlike follicular RCC, and RCC in neuroblastoma survivors. For each RCC subtype, relevant clinical, molecular, gross, and microscopic findings are reviewed, and ancillary studies helpful for its differential diagnosis are presented, providing a practical approach to modern RCC classification.

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.

Diagnostic utility of vimentin, CD117, cytokeratin-7 and caveolin-1 in differentiation between clear cell renal cell carcinoma, chromophobe renal cell carcinoma and oncocytoma

Overlapping morphological characteristics pose some difficulties in making a proper diagnosis of clear cell renal cell carcinoma (CCRCC), chromophobe renal cell carcinoma (ChRCC), and oncocytoma, on the basis of hematoxylin-eosin-stained tissue sections. Our objective was to find out a fast, reliable panel of immunohistochemical markers for differentiation between them. The study was carried out on 55 selected renal tumor specimens: 36 cases of CCRCC, seven cases of ChRCC, and 12 cases of oncocytoma. The specimens were stained immunohistochemically for vimentin, CD117, cytokeratin (CK)7, and caveolin (Cav)-1. Sensitivity and specificity for each marker were calculated. Vimentin expression was exclusively observed in CCRCC (100%) and negative in ChRCC and oncocytoma. CD117 was absent in CCRCC, but it was strongly expressed in ChRCC (85.5%) and oncocytoma (91.7%), with high sensitivity and specificity. Most CCRCCs and oncocytomas were negative for CK7 (91.7% and 83.3%, respectively), in contrast to ChRCCs, which showed positivity in nearly 86% of the cases. Good sensitivity and specificity were calculated for CK7 in differentiating studied oncocytic tumors. Cav-1 was positive in ~78% of the CCRCCs and in all ChRCCs, whereas the vast majority of oncocytomas were negative. So the immunoprofile of CCRCC was vimentin⁺/CD117^-/CK7^-/Cav-1^±, ChRCC was vimentin^-/CD117⁺/CK7⁺/Cav-1⁺, and oncocytoma was vimentin^-/CD117⁺/CK7^±/Cav-1^-. So, by using combination of four markers (vimentin, CD117, CK7, and Cav-1), we achieved excellent sensitivity and specificity for differential diagnosis of CCRCC, ChRCC and oncocytoma.

The impact of additional malignancies in patients diagnosed with gastrointestinal stromal tumors

A higher incidence of additional malignancies has been described in patients diagnosed with gastrointestinal stromal tumors (GIST). This study aimed to identify risk factors for developing additional malignancies in patients diagnosed with GIST and evaluate the impact on survival. Individuals diagnosed with GIST from 2001 to2009 were identified from the SEER database. Logistic regression was used to identify predictors of additional malignancies and Cox-proportional hazards regression used to identify predictors of survival. In the study period, 1705 cases of GIST were identified, with 181 (10.6%) patients developing additional malignancies. Colorectal cancer was the most common cancer developing within 6 months of GIST diagnosis (30%). The median time to diagnosis of a malignancy after 6 months of GIST diagnosis was 21.9 months. Older age (p < 0.0001) and extraoesophagogastric GIST (p = 0.0027) were significant prognostic factors associated with additional malignancies. The overall 5-year survival was 65%, with the presence of additional malignancies within 6 months of GIST diagnosis associated with poor overall survival (54%, HR 1.55 1.05-2.3 95% CI, p = 0.04). Predictive factors of additional malignancies in patients diagnosed with GIST are increasing age and the primary disease site. Developing additional malignancies within 6 months of GIST diagnosis is associated with poorer overall survival. Targeted surveillance may be warranted in patients diagnosed with GIST that are at high risk of developing additional malignancies.

Genetic alterations of HER genes in chromophobe renal cell carcinoma

Chromophobe (ch) renal cell carcinoma (RCC) is the 3rd most common subtype of RCC and occurs in 5% of all RCCs. Although chRCC generally demonstrates more favorable outcomes compared with other subtypes of RCC, there is a 6-7% probability of tumor progression and metastasis in this disease. The subclassification of a more aggressive subtype of chRCC may be useful for the management of this cancer. The Erb-B2 receptor tyrosine kinase 2 [also known as human epidermal growth factor receptor (HER) 2] gene has been reported to be important in chRCC. The present study aimed to further investigate the abnormalities of the HER family genes and their potential association with chRCC. Fluorescence in situ hybridization was performed on 11 chRCC tissue specimens, and the Spearman's rank correlation coefficient analysis was used to assess the results. The loss of one copy of the HER2 and HER4 genes was observed to be the major alteration of the tumor cells in all chRCC cases. Statistical data indicated that loss of the HER2 gene was strongly correlated with loss of the HER4 gene (P=0.019). The findings of previous studies were also combined for analysis, and were consistent with those of the present study. In addition, the amplification of HER1 was also strongly correlated with the amplification of HER4 (P=0.004). Furthermore, a high percentage of genetic structural rearrangements was observed in HER3 genes, which was significantly associated with amplification of HER2 (P=0.005). Certain alterations in the HER gene family were also noted as a phenomenom in chRCC. Therefore, the characterization of the underlying aberrant functions of HER genes may be of interest for additional studies in the context of using HER genes to distinguish between RCC subtypes in order to establish improved treatment guidelines.

Diagnostic approach to eosinophilic renal neoplasms

CONTEXT

Eosinophilic renal neoplasms include a spectrum of solid and papillary tumors ranging from indolent benign oncocytoma to highly aggressive malignancies. Recognition of the correct nature of the tumor, especially in biopsy specimens, is paramount for patient management.

OBJECTIVE

To review the diagnostic approach to eosinophilic renal neoplasms with light microscopy and ancillary techniques.

DATA SOURCES

Review of the published literature and personal experience.

CONCLUSIONS

The following tumors are in the differential diagnosis of oncocytic renal cell neoplasm: oncocytoma, chromophobe renal cell carcinoma (RCC), hybrid tumor, tubulocystic carcinoma, papillary RCC, clear cell RCC with predominant eosinophilic cell morphology, follicular thyroid-like RCC, hereditary leiomyomatosis-associated RCC, acquired cystic disease-associated RCC, rhabdoid RCC, microphthalmia transcription factor translocation RCC, epithelioid angiomyolipoma, and unclassified RCC. In low-grade nonpapillary eosinophilic neoplasms, distinction between oncocytoma and low-grade RCC mostly rests on histomorphology; however, cytokeratin 7 immunostain may be helpful. In high-grade nonpapillary lesions, there is more of a role for ancillary techniques, including immunohistochemistry for cytokeratin 7, CA9, CD10, racemase, HMB45, and Melan-A. In papillary eosinophilic neoplasms, it is important to distinguish sporadic type 2 papillary RCC from microphthalmia transcription factor translocation and hereditary leiomyomatosis-associated RCC. Histologic and cytologic features along with immunohistochemistry and fluorescence in situ hybridization tests for TFE3 (Xp11.2) and TFEB [t(6;11)] are reliable confirmatory tests. Eosinophilic epithelial neoplasms with architecture, cytology, and/or immunoprofile not qualifying for either of the established types of RCC should be classified as unclassified eosinophilic RCC and arbitrarily assigned a grade (low or high).

Possible prognostic and therapeutic significance of c-Kit expression, mast cell count and microvessel density in renal cell carcinoma

Renal cell carcinoma (RCC) is the most frequent renal tumor and its incidence is increasing worldwide. Tumor angiogenesis is known to play a crucial role in the etiopathogenesis of RCC and over the last few years an even deeper knowledge of its contribution in metastatic RCC development has led to the development of numerous molecular targeting agents (such as sunitinib, sorafenib, pazopanib, axitinib, tivozanib, and dovitinib). The above agents are principally directed against vascular endothelial growth factor receptor (VEGFR) members and also against c-Kit receptor (c-KitR). The role of c-kitR inhibition on clear cell RCC (ccRCC), the main RCC subtype, is less well established. Whether c-kitR activation through its ligand, stem cell factor (SCF) contributes significantly to the effects of tyrosine kinase inhibitors (TKIs) treatment remains to be established. It is important to underscore that the c-KitR is expressed on mast cells (MCs) and cancer cells. After an examination of the c-KitR/SCF pathway, we review here the principal studies that have evaluated c-Kit expression in RCC. Moreover, we summarize some investigations that have observed the distribution of MCs in primary renal cancer and in adjacent normal tissue with appropriate histological immunohistochemical techniques. We also focus on few studies that have evaluated the correlation between RCC proliferation, MC count and microvessel density (MVD), as hallmarks of tumor angiogenesis. Thus, the aim of this review of the literature is to clarify if c-KitR expression, MC count and MVD could have prognostic significance and the possible predictive therapeutic implications in RCC.

t(6;11) renal cell carcinoma (RCC): expanded immunohistochemical profile emphasizing novel RCC markers and report of 10 new genetically confirmed cases

Renal cell carcinomas (RCCs) harboring the t(6;11)(p21;q12) translocation were first described in 2001 and recently recognized by the 2013 International Society of Urological Pathology Vancouver Classification of Renal Neoplasia. Although these RCCs are known to label for melanocytic markers HMB45 and Melan A and the cysteine protease cathepsin K by immunohistochemistry (IHC), a comprehensive IHC profile has not been reported. We report 10 new t(6;11) RCCs, all confirmed by break-apart TFEB fluorescence in situ hybridization. A tissue microarray containing 6 of these cases and 7 other previously reported t(6;11) RCCs was constructed and immunolabeled for 21 different antigens. Additional whole sections of t(6;11) RCC were labeled with selected IHC markers. t(6;11) RCC labeled diffusely and consistently for cathepsin K and Melan A (13 of 13 cases) and almost always at least focally for HMB45 (12 of 13 cases). They labeled frequently for PAX8 (14 of 23 cases), CD117 (10 of 14 cases), and vimentin (9 of 13 cases). A majority of cases labeled at least focally for cytokeratin Cam5.2 (8 of 13 cases) and CD10 and RCC marker antigen (10 of 14 cases each). In contrast to a prior study's findings, only a minority of cases labeled for Ksp-cadherin (3 of 19 cases). The median H score (product of intensity score and percentage labeling) for phosphorylated S6, a marker of mTOR pathway activation, was 101, which is high relative to most other RCC subtypes. In summary, IHC labeling for PAX8, Cam5.2, CD10, and RCC marker antigen supports classification of the t(6;11) RCC as carcinomas despite frequent negativity for broad-spectrum cytokeratins and EMA. Labeling for PAX8 distinguishes the t(6;11) RCC from epithelioid angiomyolipoma, which otherwise shares a similar immunoprofile. CD117 labeling is more frequent in the t(6;11) RCC compared with the related Xp11 translocation RCC. Increased pS6 expression suggests a possible molecular target for the uncommon t(6;11) RCCs that metastasize.

Chromophobe renal cell carcinoma: a morphologic and immunohistochemical study of 45 cases

The aim of this study was to evaluate the morphological spectrum of chromophobe renal cell carcinoma (CRCC) and diagnostic utility of a panel of three immunohistochemical stains. All cases of CRCC reported between 2002 and 2012 in the Section of Histopathology, Aga Khan University Hospital, were retrieved. A total of 45 cases were identified. Slides were reviewed and immunohistochemical stains (CK7, CD117, and vimentin) were performed. Ages ranged from 18 to 90 years (mean, 48.5 years). Male-to-female ratio was 0.8:1. The tumor was located in the left kidney in 24 patients and the right kidney in 20 patients. The tumor size ranged from 3.5 to 22 cm (mean 10 cm). Histologically, 4 were classic, 22 were eosinophilic, 16 were mixed, and 3 were sarcomatoid type. Morphologic patterns included broad alveolar, solid, nested, tubular, tubulocystic, trabecular, papillary, and microglandular. Binucleation and perinuclear halos were seen in all cases. Nuclear grooves and pseudoinclusions were seen in 17 and 6 cases, respectively. Multinucleated cells were seen in 19 cases. Mitoses ranged from 1 to 11/10 HPFs (mean 3/10 HPFs). Hyalinized stroma was seen in 38 cases and calcification in 26 cases. Necrosis was seen in 18 cases. Palisading of smaller cells around the broad alveolar pattern was noted in 5 cases. The Furhman's nuclear grade was I (11), II (26), III (5), and IV (3). Hale's colloidal iron was positive in all cases. Immunohistochemical stain CK7 and CD117 were positive in 100% and 95.5% of cases respectively. Vimentin was negative in all cases, except in the sarcomatoid areas of 3 cases. In conclusion, chromophobe renal cell carcinoma has certain unique morphological features and immunohistochemical profile which help to distinguish it from conventional renal cell carcinoma and oncocytoma. We identified nuclear pseudoinclusions, microglandular pattern and palisading of smaller cells, which have not been reported earlier.

Nephrogenic adenoma: an immunohistochemical analysis using biotin-free methods

Nephrogenic adenoma (NA) has been considered as a metaplastic process of the urothelium. It has been suggested that this lesion is of renal tubular cell origin or differentiation. Immunohistochemical studies of NA emphasize its staining with α-methylacyl-coenzyme A racemase (AMACR), and prostatic adenocarcinoma may be a possible differential diagnosis. This reactivity was recently discussed as an artifact due to endogenous biotin. Kidney-specific cadherin (Ksp-cad) is a marker of distal nephron. CD10 and KIT are also expressed in the kidney. We studied the immunohistochemical expression of AMACR, p63, Ksp-cad, CD10, and KIT in 9 cases of NA (forming a total of 12 lesions). Practically all of the lesions stained for AMACR with 2 different antibodies and 2 high-sensitivity (multimer or polymer based) biotin-free methods (83% and 100%). The staining was similar for both methods in 9 of these 12 lesions. All of the NAs were negative for p63 and KIT, except 1 case, with focal reactivity for KIT. CD10 was expressed very focally in 4 of the 12 lesions (33%). We observed weak staining for Ksp-cad in 6 lesions (50%) and 3 (25%) showed a moderate positivity in 15% to 50% of the cells. In conclusion, positivity of NA for AMACR is not an artifact, as we confirmed using 2 different methods. Besides, p63, a basal cell marker, is usually negative. Immunoreactivity for Ksp-cad seems to support the differentiation of NA to distal nephron cells, at least in some of the cases. Other markers expressed by the nephron, such as CD10 and KIT, are usually negative in NA.

Predictors of response to targeted therapy in renal cell carcinoma

CONTEXT

The prognosis for patients with metastatic renal cell carcinoma is poor, with an average 5-year survival of approximately 10%. Use of traditional cytokine therapy, specifically high-dose interleukin 2, is limited by significant toxicity. Better understanding of the molecular pathogenesis of renal cell carcinoma has led to the development of targeted therapies to inhibit specific cellular pathways leading to tumorigenesis. These drugs provide improved survival with a more favorable toxicity profile. There is ongoing investigation of markers that predict response of an individual patient to different targeted therapies.

OBJECTIVE

To explain the molecular basis for vascular endothelial growth factor inhibitor (antiangiogenic) and mammalian target of rapamycin inhibitor therapies for renal cell carcinoma, summarize the clinical trials demonstrating the effectiveness of these drugs, and describe the biomarkers shown to correlate with outcome in patients treated with targeted therapy.

DATA SOURCES

All included sources are from peer-reviewed journals in PubMed (US National Library of Medicine).

CONCLUSION

Emerging evidence shows promise that biomarkers will be useful for predicting an individual patient's response to targeted therapy, leading to a more personalized approach to treating renal cell carcinoma.

Histological reclassification, histochemical characterization and c-kit immunoexpression in renal cell carcinoma

Objectives:

Renal cell carcinoma is the most lethal of all urologic malignancies. Several parameters such as histological subtype, nuclear grade and TNM staging help in determining the prognosis and treatment options. A newer therapeutic modality has been suggested based on expression of c-kit antigen by the tumor cells. This study was designed to evaluate various histological parameters and correlate them with c-kit expression.

Materials and Methods:

The study was done on 40 consecutive cases of renal epithelial tumors. Histological sections were reviewed and reclassified according to WHO (2004) classification and nuclear grade assessed. Hale's colloidal iron stain was done to identify the chromophobe variant. Immunostaining with c-kit was done and its expression was studied. The results were correlated and statistical significance was assessed.

Results:

The age range was 31-81 years, with a male to female ratio of 2:1. Seventy per cent of the cases were clear cell RCC (ClRCC), 17.5% were chromophobe type, 7.5% were papillary RCCs and 5% cases were oncocytomas. Fuhrman nuclear grading revealed 60.5% cases to be of low grade and 39.5% high grade. Hale's colloidal iron staining was positive in chromophobe RCC and oncocytomas, while it was negative in ClRCC. Immunostaining with c-kit was positive only in oncocytomas.

Conclusions:

Clear cell RCC was the most common histological subtype of RCC. Clear cell RCC known to have a poor prognosis, showed a statistically significant higher nuclear grade than chromophobe and papillary RCCs which have a better prognosis. Hale's colloidal iron staining was extremely useful in distinguishing chromophobe RCC and oncocytoma from the granular cell variant of clear RCC. Our study revealed c-kit negativity in all RCC. As Imatinib could be ineffective in such tumors, its clinical activity has to be carefully assessed in such tumors through further studies.

Current pathology keys of renal cell carcinoma

CONTEXT

Renal cell carcinoma (RCC) in adults comprises a heterogeneous group of tumours with variable clinical outcomes that range from indolent to overtly malignant. The application of molecular genetic techniques to the study of renal neoplasms has resulted in an improved classification of these entities and a better understanding of the biologic mechanisms responsible for tumour development and progression. The current 2004 World Health Organisation classification of adult renal epithelial neoplasms has expanded rapidly with new categories recently incorporated.

OBJECTIVE

To review and evaluate the evidence implicating pathologic features and classification of RCC in adults as a tool to approach patients' prognosis and modulate current therapy.

EVIDENCE ACQUISITION

Members of Committee 3: Pathology, under the auspices of the International Consultation on Urological Diseases and the European Association of Urology (ICUD-EAU) International Consultation on Kidney Cancer, performed a systematic review using PubMed. Participating pathologists discussed pathologic categories and diagnostic features of RCC in adults.

EVIDENCE SYNTHESIS

We reviewed and discussed articles and the personal experiences of participating uropathologists.

CONCLUSIONS

The conclusions reached by the ICUD-EAU 2010 International Consultation on Kidney Cancer emphasise the appropriate pathologic diagnosis of RCC in adults as a tool to approach patients' prognosis and modulate current therapy. Further emphasis should be placed on defining risk groups of RCC and diagnostic features of unusual tumours such as familial RCC, translocation RCC, and tubular mucinous and spindle cell carcinoma. A number of recently described entities and morphologic variants of classical categories deserves recognition because they can be important in differential diagnosis and therapy.

Cluster analysis of immunohistochemical profiles delineates CK7, vimentin, S100A1 and C-kit (CD117) as an optimal panel in the differential diagnosis of renal oncocytoma from its mimics

AIMS

To develop an immunohistochemical strategy for distinguishing renal oncocytoma (RO) from the eosinophilic variant of chromophobe (ChRCC), and papillary (PRCC) and clear cell (CRCC) renal cell carcinoma containing eosinophilic cytoplasm in core biopsy specimens.

METHODS AND RESULTS

Cluster analysis was performed on immunohistochemical data from 21 RO, 16 ChRCC, 16 CRCC and 20 PRCC patients. A panel of CK7, C-kit, S100A1 and vimentin clustered into four groups. Cluster A (94% ChRCC) expressed C-kit and CK7 and lacked S100A1 and vimentin. Cluster B (95% RO) expressed C-kit, S100A1, focal CK7 (single or small clusters of cells) and lacked vimentin. Cluster C comprised a mixture of PRCC and CRCC with no expression of C-kit or CK7 and variable S100A1 and vimentin. PRCC with strong expression of CK7 clustered into group D. A panel of S100A1 (positive) and focal CK7 expression distinguished RO from ChRCC with 91% sensitivity and 93% specificity. A panel of vimentin (negative) and C-kit (positive) distinguished RO from CRCC with 83% sensitivity and 86% specificity and RO from PRCC with 79% sensitivity and 88% specificity.

CONCLUSIONS

Hierarchical cluster analysis is an effective approach to analyse high-volume immunohistochemical data to generate an optimal panel in the differential diagnosis of oncocytoma from its mimics.

Immunohistochemical diagnosis of renal neoplasms

CONTEXT

Histologic diagnosis of renal neoplasm is usually straightforward by routine light microscopy. However, immunomarkers may be essential in several contexts, including differentiating renal from nonrenal neoplasms, subtyping of renal cell carcinoma (RCC), and diagnosing rare types of renal neoplasms or metastatic RCC in small biopsy specimens.

OBJECTIVE

To provide a comprehensive review of the diagnostic utility of immunomarkers for renal neoplasms.

DESIGN

This review is based on published literature and personal experience.

CONCLUSIONS

The following markers may have diagnostic utility in various diagnostic contexts: cytokeratins, vimentin, α-methylacyl coenzyme A racemase, carbonic anhydrase IX, PAX2, PAX8, RCC marker, CD10, E-cadherin, kidney-specific cadherin, parvalbumin, claudin-7, claudin-8, S100A1, CD82, CD117, TFE3, thrombomodulin, uroplakin III, p63, and S100P. Cytokeratins are uniformly expressed by RCC, albeit in a somewhat limited amount in some subtypes, requiring broad-spectrum anti-CK antibodies, including both low- and high-molecular-weight cytokeratins. PAX2 and PAX8 are sensitive and relatively specific markers for renal neoplasm, regardless of subtype. CD10 and RCC marker are sensitive to renal cell neoplasms derived from proximal tubules, including clear cell and papillary RCCs. Kidney-specific cadherin, parvalbumin, claudin-7, and claudin-8 are sensitive markers for renal neoplasms from distal portions of the nephron, including chromophobe RCC and oncocytoma. CK7 and α-methylacyl coenzyme A racemase are sensitive markers for papillary RCC; TFE3 expression is essential in confirming the diagnosis of Xp11 translocation RCC. The potentially difficult differential diagnosis between chromophobe RCC and oncocytoma may be facilitated by S100A1 and CD82. Thrombomodulin, uroplakin III, p63, and S100P are useful markers for urothelial carcinoma. Together with high-molecular-weight cytokeratins, PAX2, and PAX8, they can help differentiate renal pelvic urothelial carcinoma from collecting duct RCC. A sensitive marker for sarcomatoid RCC is still not available. Immunomarkers are most often used for diagnosing metastatic RCC. Compared with primary RCC, expression of the above-mentioned markers is often less frequent and less diffuse in the metastatic setting. Recognizing the variable sensitivity and specificity of these markers, it is important to include at least CD10, RCC marker, PAX2, and PAX8 in the diagnostic panel.

Chromophobe Renal Cell Carcinoma with Sarcomatoid Transformation in a Dog

A 12-year-old spayed female Siberian husky dog presented with hematuria and weight loss. An abdominal ultrasonographic examination revealed a left renal tumor measuring 8 cm in diameter, and a nephrectomy was performed. The resected kidney contained a cavitated tumor with a white solid region. Histologically, this tumor was composed of large polygonal cells with abundant and cloudy cytoplasm and focal sarcomatoid change. The neoplastic epithelial cells were reactive with colloidal iron staining; Dolichos biflorus agglutinin, peanut agglutinin, and Ulex europaeus agglutinin I lectins; and cluster of differentiation 10 and c-KIT antigens but not for periodic acid-Schiff or vimentin stain. Neoplastic sarcomatoid cells stained positive for vimentin. Because these histopathologic features are identical to those of human chromophobe renal cell carcinoma, the present case was diagnosed as canine chromophobe renal cell carcinoma.

Molecular pathology of renal oncocytoma: a review

Differentiating renal oncocytoma from its renal cell carcinoma (RCC) mimics, particularly chromophobe RCC, can be difficult, especially when limited tissue is available for evaluation and requires sophisticated microscopic, ultrastructural and immunohistochemical evaluation. In this review, the relevant literature has been reviewed, and supporting data obtained by applying modern microarray-based technologies are discussed with a focus on molecular pathology of renal oncocytoma. The high resolution whole-genome DNA-microarray based analyses excluded with all certainty the occurrence of small specific alterations. Renal oncocytomas are characterized by variable chromosomal patterns. The number of genes selected by global gene expression analyses and their usefulness in the diagnostic pathology based on immunohistochemical evaluation is far below the expectations. The conflicting staining patterns, together with the poor specificity of proposed antibodies, leads us to believe that these candidate immunomarkers might not help in the separation of these tumors. Applying DNA based tools might help in the diagnosis of renal oncocytoma with uncertain histology. However, only the combination of all available techniques could give reliable information.

Expression of PAX8 in normal and neoplastic renal tissues: an immunohistochemical study

Cell-lineage-specific transcription factors are a group of regulatory proteins expressed in embryonic, differentiated, or neoplastic cells of the same lineage and represent a valuable repertoire of tissue-specific markers for the diagnosis of human tumors. Together with PAX2, PAX8 is a nephric-lineage transcription factor and is required for the establishment of renal-lineage cells and the formation of the kidney. In contrast to PAX2, little is known about the expression of PAX8 in adult kidney and renal tumors. In this study, we used immunohistochemistry to investigate the expression of PAX8 in adult human kidney and renal epithelial tumors. We report here that PAX8 was detected in renal epithelial cells in all segments of renal tubules from the proximal tubules to the renal papillae and in the parietal cells of Bowman's capsule in the adult kidney. PAX8 was also present in 98% of clear cell renal cell carcinomas (RCCs), 90% of papillary RCCs, and 95% of oncocytomas, similar to PAX2. In addition, PAX8 was found in 82% of chromophobe RCCs, 71% of sarcomatoid components of RCCs, and 100% (2/2) of renal medullary carcinomas. Overall, PAX8 was detected in 85% of metastatic renal tumors. Interestingly, expression of PAX8 was noted in some urothelial cells in the renal pelvis and ureters and approximately 23% of urothelial carcinomas of the renal pelvis, but not in the urothelium or urothelial carcinomas of the urinary bladder; this probably underlines the different embryonic origins of urothelial cells in the upper and lower urinary tracts. As shown in this study, PAX8 is widely expressed in normal and neoplastic renal tissues. PAX8 may be a useful additional marker for renal epithelial tumors; however, its specificity and sensitivity await further investigation.

Molecular Pathology of the Genitourinary Tract: Molecular Pathology of Kidney and Testes

With the advent of newer molecular technologies, our knowledge of cellular mechanisms with tumors of the kidney and testis has grown exponentially. Molecular technologies have led to better understanding of interplay between the von Hippel-Lindau gene and angiogenic cytokines in renal cancer and isochromosome 12p in testicular neoplasms. The result has been development of antiangiogenic-targeted therapy within recent years that has become the mainstay treatment for metastatic renal cell cancer. In the near future, classification and diagnosis of renal and testicular tumors through morphologic analysis will be supplemented by molecular information correlating to prognosis and targeted therapy. This article outlines tumor molecular pathology of the kidney and testis encompassing current genomic, epigenomic, and proteonomic findings.

Origin of renal cell carcinomas

Cancer is a heritable disorder of somatic cells: environment and heredity are both important in the carcinogenic process. The primal force is the "two hits" of Knudson's hypothesis, which has proved true for many tumours, including renal cell carcinoma. Knudson et al. [1, 2] recognised that familial forms of cancer might hold the key to the identification of important regulatory elements known as tumour-suppressor genes. Their observations (i.e., that retinoblastoma tend to be multifocal in familial cases and unifocal in sporadic presentation) led them to propose a two-hit theory of carcinogenesis. Furthermore, Knudson postulated that patients with the familial form of the cancer would be born with one mutant allele and that all cells in that organ or tissue would be at risk, accounting for early onset and the multifocal nature of the disease. In contrast, sporadic tumours would develop only if a mutation occurred in both alleles within the same cell, and, as each event would be expected to occur with low frequency, most tumours would develop late in life and in a unifocal manner [3, 4]. The kidney is affected in a variety of inherited cancer syndromes. For most of them, both the oncogene/tumour-suppressor gene involved and the respective germline mutations have been identified. Each of the inherited syndromes predisposes to distinct types of renal carcinoma. Families with hereditary predisposition to cancer continue to provide a unique opportunity for the identification and characterisation of genes involved in carcinogenesis. A surprising number of genetic syndromes predispose to the development of renal cell carcinoma, and genes associated with five of these syndromes have been already identified: VHL, MET, FH, BHD and HRPT2. Few cancers have as many different types of genetic predisposition as renal cancer, although to date only a small proportion of renal cell cancers can be explained by genetic predisposition.

Collecting duct carcinoma of the kidney: an immunohistochemical evaluation of the use of antibodies for differential diagnosis

Collecting duct carcinoma is a highly aggressive renal epithelial malignancy, although it accounts for less than 1% of the incidence of renal epithelial neoplasms. Differential diagnoses between collecting duct carcinoma, pelvic urothelial carcinoma with marked invasion to the renal parenchyma (invasive urothelial carcinoma), and papillary renal cell carcinoma is often challenging. In our current study, we examined the utility of using commercially available antibodies, in conjunction with lectin histochemistry, for such differential diagnoses. We examined 17 cases of collecting duct carcinoma, 10 cases of invasive urothelial carcinoma and 15 cases of papillary renal cell carcinoma (type 1, 6 cases; type 2, 9 cases) in these evaluations. Our results indicated that Ulex europaeus agglutinin 1, E-cadherin, and c-KIT were frequently positive in collecting duct carcinoma and invasive urothelial carcinoma, in comparison with papillary renal cell carcinoma, which had negative results for CD10 and alpha-methylacyl CoA racemase. We found, however, that collecting duct carcinoma showed positivity for high-molecular-weight cytokeratin and low-molecular-weight cytokeratin at a low frequency compared with invasive urothelial carcinoma, and that these distinctions need further careful evaluation. In addition, high-molecular-weight cytokeratin positivity was not a reliable marker for collecting duct carcinoma. We conclude that Ulex europaeus agglutinin 1 reactivity and positivity for E-cadherin and c-KIT are effective in distinguishing collecting duct carcinoma from papillary renal cell carcinoma, and that negative results for alpha-methylacyl CoA racemase and CD10 are potentially useful hallmarks of this distinction also. In contrast, a differential diagnosis for collecting duct carcinoma and invasive urothelial carcinoma will require careful examination of multiple routinely stained specimens, particularly in cases of in situ neoplastic lesions in the pelvic mucosa.

Application of Immunohistochemistry to the Genitourinary System (Prostate, Urinary Bladder, Testis, and Kidney)

Context.—The variety of morphologic patterns of different entities of the genitourinary tract can present a diagnostic dilemma for the pathologist. This is especially true in cases of mimics of cancer, a cancer of unknown primary, or poorly differentiated tumors, in which it is hard to assign histogenesis needed to plan the correct therapy for the patient. Immunohistochemistry offers a better capacity than hematoxylin-eosin staining alone to differentiate human tissue types. Also, in the past decades, several techniques had been developed to differentiate between benign and malignant processes with morphologic overlap. By using immunohistochemistry in selected cases, the rate of false-negative and false-positive diagnoses can be reduced, and some patients are afforded the opportunity to get more specific or effective therapy as a result.

Objective.—For each subgroup of genitourinary system tumors, common diagnostic problems are reviewed, and immunohistochemical markers useful in addressing these problems are discussed, along with expected patterns of immunoreactivity.

Data Sources.—The pertinent literature, with focus on immunohistochemical staining of tumors of the genitourinary tract.

Conclusions.—The addition of immunohistochemistry to the diagnostic armamentarium for genitourinary pathologic diagnosis has increased the sensitivity and specificity of diagnoses and aided in the selection of optional therapeutic regimens in selected cases.

Renal epithelial neoplasms: diagnostic applications of gene expression profiling

Renal cell carcinoma (RCC) is the most common form of kidney cancer in adults. RCC is a significant challenge for pathologic diagnosis and clinical management. The primary approach to diagnosis is by light microscopy, using the World Health Organization (WHO) classification system, which defines histopathologic tumor subtypes with distinct clinical behavior and underlying genetic mutations. However, light microscopic diagnosis of RCC subtypes can be difficult due to variable histology, morphologic features shared by tumor subtypes, and a growing frequency of small tumor biopsies with limited morphologic information. In addition to these diagnostic problems, the clinical behavior of RCC is highly variable, and therapeutic response rates are poor. Few clinical assays are available to predict outcome in RCC or correlate behavior with histology. Therefore, novel RCC classification systems based on gene expression should be useful for diagnosis, prognosis, and treatment. Recent microarray studies have shown that renal tumors are characterized by distinct gene expression profiles, which can be used to discover novel diagnostic and prognostic biomarkers. Here, we review clinical features of kidney cancer, the WHO classification system, and the growing role of molecular classification for diagnosis, prognosis, and therapy of this disease.

Profiling and classification tree applied to renal epithelial tumours

AIMS

Selection of the relevant combination from a growing list of candidate immunohistochemical biomarkers constitutes a real challenge. The aim was to establish the minimal subset of antibodies to achieve classification on the basis of 12 antibodies and 309 renal tumours.

METHODS AND RESULTS

Seventy-nine clear cell (CC), 88 papillary (PAP) and 50 chromophobe (CHRO) renal cell carcinomas, and 92 oncocytomas (ONCO) were immunostained for renal cell carcinoma antigen, vimentin, cytokeratin (CK) AE1-AE3, CK7, CD10, epithelial membrane antigen, alpha-methylacyl-CoA racemase (AMACR), c-kit, E-cadherin, Bcl-1, aquaporin 1 and mucin-1 and analysed by tissue microarrays. First, unsupervised hierarchical clustering performed with immunohistochemical profiles identified four main clusters-cluster 1 (CC 67%), 2 (PAP 98%), 3 (CHRO 67%) and 4 (ONCO 100%)-demonstrating the intrinsic classifying potential of immunohistochemistry. A series of classification trees was then automatically generated using Classification And Regression Tree software. The most powerful of these classification trees sequentially used AMACR, CK7 and CD10 (with 86% CC, 87% PAP, 79% CHRO and 78% ONCO correctly classified in a leave-one-out cross-validation test). The classifier was also helpful in 22/30 additional cases with equivocal features.

CONCLUSION

The classification tree method using immunohistochemical profiles can be applied successfully to construct a renal tumour classifier.

Immunohistochemical analysis of chromophobe renal cell carcinoma, renal oncocytoma, and clear cell carcinoma: an optimal and practical panel for differential diagnosis

CONTEXT

The separation of chromophobe renal cell carcinoma, oncocytoma, and clear cell renal cell carcinoma using light microscopy remains problematic in some cases.

OBJECTIVE

To determine a practical immunohistochemical panel for the differential diagnosis of chromophobe carcinoma.

DESIGN

Vimentin, glutathione S-transferase alpha (GST-alpha), CD10, CD117, cytokeratin (CK) 7, and epithelial cell adhesion molecule (EpCAM) were investigated in 22 cases of chromophobe carcinoma, 17 cases of oncocytoma, and 45 cases of clear cell carcinoma.

RESULTS

Vimentin and GST-alpha expression were exclusively observed in clear cell carcinoma. CD10 staining was more frequently detected in clear cell carcinoma (91%) than in chromophobe carcinoma (45%) and oncocytoma (29%). CD117 was strongly expressed in chromophobe carcinoma (82%) and oncocytoma (100%), whereas none of the cases of clear cell carcinomas were immunoreactive. Cytokeratin 7 was positive in 18 (86%) of 22 cases of chromophobe carcinoma, whereas all oncocytomas were negative for CK7. EpCAM protein was expressed in all 22 cases of chromophobe carcinoma in more than 90% of cells, whereas all EpCAM-positive oncocytomas (5/17; 29%) displayed positivity in single cells or small cell clusters.

CONCLUSIONS

Using the combination of 3 markers (vimentin, GST-alpha, and EpCAM), we achieved 100% sensitivity and 100% specificity for the differential diagnosis of chromophobe carcinoma, oncocytoma, and clear cell carcinoma. The pattern of "vimentin(-)/GST-alpha(-)" effectively excluded clear cell carcinoma, and homogeneous EpCAM expression confirmed the diagnosis of chromophobe carcinoma rather than oncocytoma. CD117 and CK7 were also useful markers and could be used as second-line markers for the differential diagnosis, with high specificity (100%) and high sensitivity (90% and 86%, respectively).

Angiomyolipoma with epithelial cysts (AMLEC): a rare but distinct variant of angiomyolipoma

Angiomyolipoma with epithelial cysts (AMLEC) is a recently described distinct cystic variant of angiomyolipoma (AML). To date 15 cases of AMLEC have been reported in 2 case series. We report the 16th case in a 39-year-old female. Her left kidney tumor was discovered incidentally. Partial nephrectomy was performed. Histologically, the tumor was composed of three components: 1) epithelial cysts lined by cuboidal to hobnail cells; 2) compact subepithelial mullerian-like AML stroma with admixed chronic inflammation; and 3) muscle-predominant AML with dysmorphic blood vessels exterior to the subepithelial stroma. Immunohistochemically, the subepithelial stroma stained most intensely with HMB-45 and Melan-A, whilst the muscle-predominant AML areas stained most intensely with smooth muscle actin and desmin. Estrogen receptor (ER), progesterone receptor (PR), and CD10 stained most intensely in the subepithelial stroma. The cyst lining was positive for pancytokeratin, but negative for HMB-45, Melan-A, ER, PR, and CD10. The patient is alive with no evidence of disease, 12 months postoperatively, and yearly follow-up CT scans are planned.

ARPP protein is selectively expressed in renal oncocytoma, but rarely in renal cell carcinomas

We have recently isolated a gene, Ankyrin-repeated protein with a proline-rich region (ARPP), that is highly expressed in the skeletal and cardiac muscle. Our previous immunohistochemical analysis revealed that ARPP expression was augmented in rhabdomyosarcoma but scarcely detectable in leiomyosarcoma, showing that ARPP is a useful marker for rhabdomyosarcoma. In the present study, we generated the anti-ARPP monoclonal antibody, YAS11, immunoreactive with the N-terminal region (amino-acids residues 1-145) of the ARPP protein. Further, we immunohistochemically analyzed 100 renal tumors including 14 oncocytomas, and 86 renal cell carcinomas (RCCs). We found that ARPP was highly expressed in 12 of the 14 (85.7%) oncocytomas, but was detectable in only four of the 86 (4.7%) RCCs. Interestingly, ARPP was not detected in any of 11 chromophobe RCCs, suggesting that ARPP may be useful for differential diagnosis between oncocytoma and chromophobe RCC. Furthermore, we found that ARPP was selectively expressed in part of the distal renal tubule in normal kidney. Immunoelectron microscopy with anti-ARPP antibody revealed that ARPP was localized in mitochondria and nuclei in both the normal distal renal tubule and oncocytoma, suggesting that oncocytoma may be derived from the distal nephron, and probably from part of the distal renal tubule.

Monotypic epithelioid angiomyolipoma of the kidney: a case report

A case of monotypic variant of epithelioid angiomyolipoma (AML) observed in a 62-year old woman is reported. The patient complained of abdominal fullness caused by a huge left renal mass without evidence of tuberous sclerosis complex. Imaging studies showed a left renal mass with an area showing hemorrhage and necrosis. The left renal mass, spleen and pancreatic tail were removed en bloc transabdominally. The resected tumor weighed 1200 g and showed focal necrosis and hemorrhage. Microscopically, the tumor was composed exclusively of atypical polygonal cells with copious eosinophilic cytoplasm, pleomorphic nuclei and prominent nucleoli. Tumor cells were considered to derive from perivascular epithelioid cells, and exhibited strong positive staining for HMB-45 and c-KIT, but were negative for epithelial, smooth muscle, and neural markers. As this tumor had none of the typical elements of classic AML, the final pathological diagnosis was monotypic epithelioid AML.

[Gastrointestinal stromal tumors: definition, histological, immunohistochemical, and molecular features, and diagnostic strategy]

Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal tumors of the gastrointestinal tract. Major advances in their definition and classification and the understanding of their molecular mechanisms have recently been made. These advances have resulted in the delineation of a treatment that has become a model of targeted therapy in oncology. GISTs are defined as tumors of the gastrointestinal tract, but also of the mesentery and peritoneum, constituted by a proliferation of usually spindle-shaped, rarely epithelioid cells, usually, but not consistently expressing the KIT protein. Most GISTs are associated with molecular abnormalities in two target genes: KIT (which encodes the KIT protein) and PDGFRA (which encodes the A chain of the PDGF receptor). The diagnosis of GIST relies on histological arguments (proliferation of spindle-shaped cells in 70% of cases, of epithelioid cells in 20%; histological variants are rare and sometimes misleading) and on immunohistochemical arguments (expression of KIT in 95%, usually associated with CD34 expression in 60%-70% of cases). The demonstration of mutations in target genes is required only in cases that are histologically suggestive but KIT-negative; beyond this indication, this is only undertaken in research protocols. The differential diagnosis of GIST includes the other mesenchymal tumors of the gastrointestinal tract, such as leiomyomas and leiomyosarcomas, and the digestive locations of some sarcomas; it relies on both histological and immunohistochemical arguments. The evaluation of the prognosis is essential. According to the current concept, every GIST carries a risk of malignancy, which may vary from very low to very high. Prognosis is based on a simple algorithm using two histoprognostic parameters, i.e., tumor size and mitotic index. The treatment of localized GIST is surgical resection, which must be complete; that of advanced or unresectable GIST is based on the use of a targeted therapy, imatinib, which is a pharmacological antagonist of the KIT protein. Proper understanding and utilisation of the diagnostic criteria and classification of GIST by pathologists are essential for good patient management.

An immunohistochemical approach to the differential diagnosis of renal tumors

Renal neoplasms comprise several distinct clinicopathologic entities with potential prognostic and the rapeutic differences. Although careful morphologic examination using sections stained with hematoxylin and eosin will allow for the correct diagnosis in the majority of cases, there is sufficient overlap between several entities such that ancillary techniques may be necessary to arrive at the correct diagnosis. In routine diagnostic surgical pathology practice of renal tumors, immunohistochemistry is the foremost ancillary technique. Using an approach based on common histologic patterns (tumors with clear cytoplasm, granular cytoplasm, tubulopapillary architecture, spindle cell morphology, small round-cell morphology, and infiltrating poorly differentiated carcinoma), we will discuss the utility of immunohistochemistry in the differential diagnosis of renal neoplasms. In recent years, needle biopsies from renal masses are being increasingly performed. In these small biopsies, the entire range of cytoarchitectural features that are generally necessary to make a diagnosis may not be fully appreciated. Immunohistochemistry may be helpful in this setting to narrow the differential diagnosis or to arrive at a definitive diagnosis. Finally, the use of immunohistochemistry for the confirmation of metastatic renal cell carcinoma presenting at distant sites will be discussed. Panels of immunohistochemical stains are proposed for different settings, including renal cell carcinoma (RCC) marker, CD10, and vimentin to suggest renal origin of a metastatic tumor, and markers to aid in subclassification of RCC, including parvalbumin and c-kit for chromophobe RCC, and cytokeratin 7 and alpha-methyl-acyl-CoA racemase for papillary RCC.

KIT (CD117): a review on expression in normal and neoplastic tissues, and mutations and their clinicopathologic correlation

CD117 (KIT) is a type III receptor tyrosine kinase operating in cell signal transduction in several cell types. Normally KIT is activated (phosphorylated) by binding of its ligand, the stem cell factor. This leads to a phosphorylation cascade ultimately activating various transcription factors in different cell types. Such activation regulates apoptosis, cell differentiation, proliferation, chemotaxis, and cell adhesion. KIT-dependent cell types include mast cells, some hematopoietic stem cells, germ cells, melanocytes, and Cajal cells of the gastrointestinal tract, and neoplasms of these cells are examples of KIT-positive tumors. Other KIT-positive normal cells include epithelial cells in skin adnexa, breast, and subsets of cerebellar neurons. KIT positivity has been variably reported in sarcomas such as angiosarcoma, Ewing sarcoma, synovial sarcoma, leiomyosarcoma, and MFH; results of the last three are controversial. The variations in published data may result from incomplete specificity of some polyclonal antibodies, possibly contributed by too high dilutions. Also, KIT is expressed in pulmonary and other small cell carcinomas, adenoid cystic carcinoma, renal chromophobe carcinoma, thymic, and some ovarian and few breast carcinomas. A good KIT antibody reacts with known KIT positive cells, and smooth muscle cells and fibroblasts are negative. KIT deficiency due to hereditary nonsense/missense mutations leads to disruption of KIT-dependent functions such as erythropoiesis, skin pigmentation, fertility, and gastrointestinal motility. Conversely, pathologic activation of KIT through gain-of-function mutations leads to neoplasia of KIT-dependent and KIT-positive cell types at least in three different systems: mast cells/myeloid cells--mastocytosis/acute myeloid leukemia, germ cells--seminoma, and Cajal cells--gastrointestinal stromal tumors (GISTs). KIT tyrosine kinase inhibitors such as imatinib mesylate are the generally accepted treatment of metastatic GISTs, and their availability has prompted an active search for other treatment targets among KIT-positive tumors such as myeloid leukemias and small cell carcinoma of the lung, with variable and often nonconvincing results.

Aplicación clínica de las actuales clasificaciones del cáncer renal

The purpose of classifying neoplasias is to recognize groups with similar progress and prognosis and, if possible, receiving the same treatment. This is why those classifications are systematically being submitted to review and improvement through the new technologies. Differentiation of various entities in renal cancer has been comparatively fast, as the new genetic and molecular discoveries have confirmed the morphologic criteria of the different cell types, thus making it possible to open new therapeutic pathways. Using the current WHO classification we recognize subtypes with excellent prognosis (Multilocular cystic renal carcinoma, Type I renal papillary carcinoma, Tubular and fusocellular mucinous carcinoma), other very aggressive ones (Bellini's collecting duct carcinoma, Medullary carcinoma), and also that the sarcomatoid transformation, even in small areas, impacts the prognosis negatively. Childhood-characteristic renal carcinomas associated with chromosome translocations have been recognized (genetic fusion TFE3 or TFEB), as well as the family forms of renal carcinoma. Regarding the UICC (International Union Against Cancer) classification, there are a series of aspects under argument (size, venous invasion, microvascular invasion, invasion of the adipous tissue of the renal sinus) that shall be discussed too, since it is possible that some modifications of the TNM might occur in the near future.