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

Rare Expression of KIT and Absence of KIT Mutations in High Grade Renal Cell Carcinoma

PURPOSE

RCCs with sarcomatoid differentiation have been reported to frequently express KIT protein, suggesting that imatinib mesylate (STI-571 or Gleevectrade mark) may be effective treatment for these aggressive tumors. We determined the frequency of KIT expression and mutation in a large series of high grade RCCs.

MATERIALS AND METHODS

We identified 194 patients who underwent nephrectomy for unilateral, sporadic nuclear grade 4 RCC between 1970 and 2002, including 123 with sarcomatoid differentiation. Sections from representative paraffin embedded tissue blocks were immunostained in an autostainer using ethylenediaminetetraacetic acid antigen retrieval, a polyclonal KIT antibody and the avidin-biotin peroxidase complex method. Mutational analysis was performed in all immunopositive and select negative cases by polymerase chain reaction amplification of KIT exons 9, 11, 13 and 17.

RESULTS

Only 7 tumors (3.6%) showed KIT expression, including 5 of the 123 (4.1%) with sarcomatoid differentiation. Four of the 7 tumors showed focal staining only. No mutations were identified in the 7 positive cases or in 8 randomly selected negative samples. Death from RCC occurred in all 7 patients with KIT positive tumors at a median of 0.6 years (range 0.3 to 2.3) and in 139 of 187 with KIT negative tumors at a median of 0.8 years (range 0 to 10.2).

CONCLUSIONS

KIT expression was identified in less than 5% of high grade RCCs with or without sarcomatoid differentiation but none of the tumors showed KIT mutations. These findings indicate that imatinib therapy is unlikely to be effective in patients with high grade RCC.

Adult Papillary Renal Tumor With Oncocytic Cells

We report a series of 10 oncocytic renal papillary tumors, with the aim of determining their clinicopathologic features. All patients were male (median age, 71 years), treated by radical nephrectomy and free of recurrence or metastasis (median follow-up, 62 months). Tumors (median size, 3.3 cm) were intrarenal and well limited, with no extrarenal extension. They consisted of thin, nonfibrotic papillae lined by a single layer of oncocytic cells, with finely granular eosinophilic cytoplasm and round regular nucleus exhibiting central nucleolus (Fuhrman grade II, except for one grade III). Foci of necrosis were present in most cases. All tumors were immunoreactive for alpha-methylacyl-coenzyme A racemase, vimentin, and CD10; 4 expressed renal cell carcinoma antigen and 3 cytokeratin 7. There were a low number of cytogenetic changes in the 5 analyzed cases (median, 4; range, 1-7), with no trisomy 7 or 17. Papillary architecture, necrosis, and immunohistochemical profiles argued against the diagnosis of oncocytoma and suggested our cases to be part of the papillary renal cell carcinoma group. However, the cases were atypical for type 1 papillary carcinoma (due to oncocytic cells and absence of trisomy 17) and for type 2 (due to a good outcome). These results suggest that adult papillary renal tumors with oncocytic cells might be a distinct variant in the papillary renal cell carcinoma group.

The role of c-kit and imatinib mesylate in uveal melanoma

Background

Uveal melanoma (UM) is the most common primary intraocular tumor in adults, leading to metastasis in 40% of the cases and ultimately to death in 10 years, despite local and/or systemic treatment. The c-kit protein (CD117) is a membrane-bound tyrosine kinase receptor and its overexpression has been observed in several neoplasms. Imatinib mesylate is a FDA approved compound that inhibits tyrosine quinase receptors, as well as c-kit. Imatinib mesylate controls tumor growth in up to 85% of advanced gastrointestinal stromal tumors, a neoplasia resistant to conventional therapy.

Methods

Fifty-five specimens of primary UM selected from the archives of the Ocular Pathology Laboratory, McGill University, Montreal, Canada, were immunostained for c-kit. All cells displaying distinct immunoreactivity were considered positive. Four human UM cell lines and 1 human uveal transformed melanocyte cell line were tested for in vitro proliferation Assays (TOX-6) and invasion assay with imatinib mesylate (concentration of 10 μM).

Results

The c-kit expression was positive in 78.2% of the UM. There was a statistical significant decrease in the proliferation and invasion rates of all 5 cell lines.

Conclusion

The majority of UM expressed c-kit, and imatinib mesylate does decrease the proliferation and invasion rates of human UM cell lines. These results justify the need for a clinical trial to investigate in vivo the response of UM to imatinib mesylate.

Composite distal nephron-derived renal cell carcinoma with chromophobe and collecting duct carcinomatous elements

Chromophobe renal cell carcinoma (RCC) and collecting duct carcinoma (CDC) are derived from the collecting duct epithelia, although their morphology, molecular biologic characteristics and clinical behaviors are quite different. Herein is presented a case of RCC possessing the chromophobe RCC and CDC elements occurring in a 64 year-old Japanese woman. The patient was referred to Yokohama City University Hospital with complaints of persistent back pain and fever. Radiologic examinations revealed a left renal tumor, and radical nephrectomy was performed. The patient died with multiple metastases, 8 months after the operation. The resected tumor showed an invasive growth, and its cut surface was heterogenous with hemorrhage and necrosis. Histologically, the tumor was composed of chromophobe elements with dedifferentiation, and CDC elements. The chromophobe and CDC elements had obvious histological transition. Lectin histochemistry and immunohistochemistry confirmed that this tumor was derived from the distal nephron. c-KIT, p53 and Ki67 antigen showed differential localization between the chromophobe and CDC elements, even in the transitional areas. Along with the previous reports, the present case seemed to be composite RCC derived from the collecting duct, which might present clues to elucidate carcinogenesis in the distal nephron.

KIT expression in normal and neoplastic renal tissues: Immunohistochemical and molecular genetic analysis

Renal chromophobe cell carcinomas (ChCC) and oncocytomas express KIT. This character seems to reflect their common histogenesis from distal nephrons. In the normal kidney, however, the expression and localization of KIT are unclear. KIT expression in angiomyolipoma and congenital mesoblastic nephroma (CMN), is still controversial. c-kit mutations are reportedly rare in ChCC, but there is little information in other renal neoplasms, and no reported data on mutations of platelet-derived growth factor receptor (PDGFR). In order to address these issues the authors examined five ChCC, five oncocytomas, seven papillary cell carcinomas, two collecting duct carcinomas, 12 angiomyolipomas, and three CMN, as well as 10 normal renal tissues. In the normal kidney KIT was specifically expressed in the distal nephrons. Nine of 12 (75%) angiomyolipomas contained scattered KIT-positive cells, whereas all three CMN were completely negative for KIT. The presence of KIT-positive cells in angiomyolipomas was likely to correspond to that of melanocytic marker-positive cells, which mainly showed epithelioid morphology. Polymerase chain reaction-single-strand conformation polymorphism showed no evidence of mutations of c-kit or PDGFR in any of the tumors examined.

Expression of KIT (CD117) in renal cell carcinoma and renal oncocytoma

OBJECTIVE

Overexpression of KIT (CD117), a tyrosine kinase receptor, has been reported in a variety of tumors, some of which are susceptible to therapy with imatinib mesylate. Our aim was to analyze KIT expression immunohistochemically in renal cell carcinomas (RCCs) and in oncocytomas.

METHODS

Routinely processed, paraffin-embedded specimens from 61 RCCs and 13 renal oncocytomas were investigated immunohistochemically. Cytoplasmic and membrane-bound KIT staining of tumor cells was determined semiquantitatively. A subset of cases was additionally analyzed for point mutations of c-kit exon 17 by peptide nucleic acid-mediated nested polymerase chain reaction-clamping.

RESULTS

All cases of oncocytomas and chromophobe RCCs showed membrane-bound KIT positivity, while about three-quarters of cases showed cytoplasmic reactivity. All other types of RCC were found KIT negative. Within the group of chromophobe RCCs, negative cytoplasmatic KIT reactivity was significantly correlated with advanced tumor stage (pT > or = 2; p = 0.036). Analysis of c-kit exon 17 revealed no 'gain-of-function' mutation like the codon 816 Asp-->Val mutation (D816V).

CONCLUSIONS

KIT expression is a hallmark of oncocytoma and chromophobe RCC. Since all other types of RCC were found to be KIT negative, immunohistochemical KIT reactivity may be used as an additional diagnostic criterion to distinguish chromophobe RCC from other RCC types. KIT reactivity and the absence of c-kit mutation D816V in chromophobe RCC justify speculations that imatinib mesylate therapy could be effective in patients with advanced disease.

The usefulness of immunohistochemical markers in the differential diagnosis of renal neoplasms

Histologic subtyping of RCC has been shown to be of prognostic value; therefore, it is important to classify malignant epithelial tumors of the kidney correctly and also to differentiate them from benign ones. Overlapping morphologic features of renal tumors sometimes make histologic subtyping difficult. The accurate diagnosis and classification of RCC are based on cytoarchitectural features and require correlation with immunophenotype and cytogenetic characteristics. RCC Ma and CD10, two markers with relative renal specificity, have been used to confirm a diagnosis of suspected RCC and can facilitate the accurate diagnosis of metastatic RCC, in particular, in FNA. Although CCRCC and PRCC share most immunomarkers, CK7 and AMACR expression can be helpful in the differential diagnosis of challenging histologic variants of the two. In addition, E-cadherin aids in the distinction between types 1 and 2 PRCC. Useful markers in the differential diagnosis between ChRCC and CCRCCare CK7, RCC Ma, CD10, VIM, CD117, parvalbumin, and E-cadherin. We propose CK7/CK20/CD15 as a useful primary immunopanel to differentiate ChRCC from ONC reliably.

Oncocytic renal neoplasms: diagnostic considerations

Advances in our understanding of renal neoplasia have resulted in recognition of numerous tumors that are composed predominantly of cells with abundant eosinophilic cytoplasm. This article discusses the features of renal oncocytoma (including oncocytosis), chromophobe renal cell carcinoma (RCC), and clear cell RCC; explores the relationship between renal oncocytoma and chromophobe RCC; briefly discusses other tumors with abundant eosinophilic cytoplasm; and emphasizes the differential diagnosis of such tumors.

S100A1 and KIT gene expressions in common subtypes of renal tumours

AIM

The aim of this study is to evaluate the S100A1 and KIT as gene markers for the differentiation of common subtypes of renal tumours.

METHODS

Fifty-five tissue samples (15 clear cell RCCs, 15 papillary RCCs, 7 chromophobe RCCs, 8 oncocytomas and 10 normal renal tissues) were studied The gene expressions of S100A1 and KIT were analysed by one-step RT-PCR by using the specific primers.

RESULTS

S100A1 was expressed in 2/15 clear cell RCCs, 11/15 papillary RCCs, 7/8 oncocytomas and in 0/7 chromophobe RCCs. KIT gene was expressed in 6/7 chromophobe RCCs and 7/8 oncocytomas while 0/15 clear cell RCCs and 1/15 papillary RCCs expressed kit gene. Normal tissue expressed neither S100A1 nor KIT gene.

CONCLUSION

S100A1 and KIT can be used as gene markers for the differentiation of common subtypes of renal tumours.

Chromophobe renal cell carcinoma with microcystic and adenomatous arrangement and pigmentation—a diagnostic pitfall. Morphological, immunohistochemical, ultrastructural and molecular genetic report of 20 cases

We present clinical, morphological, immunohistochemical, ultrastructural and molecular genetic features of 20 cases of a peculiar form of chromophobe renal cell carcinoma (CRCC) with morphology differing from that of conventional CRCC. Microscopically, the typical features of the tumors were microcystic arrangement and formation of adenomatous structures. Microcystic areas were composed of smaller eosinophilic and bigger pale cells having cytological appearance typical of conventional CRCC. Cytological features of the adenomatous structures were mostly different from those of conventional CRCC. They had a typical columnar arrangement with nuclei positioned at the base of the glandular structures and a small amount of a deeply eosinophilic cytoplasm often endowed with brush border facing the lumen of the glands. In addition, all the tumors showed a brown pigmentation. The pigmentation was located mostly extracellularly, where it formed pools of heavy deposits. Microscopic calcifications present in all cases formed psammoma bodies or else the calcifications were more extensive and amorphous in shape. Ultrastructurally, the cells showed features characteristic of CRCC: typical cytoplasmic vesicles were 100-700 nm in size and mitochondria had tubulovesicular, lamellar or circular cristae. Some tumor cells contained dark, variously sized electron-dense pigment granules. Neither melanosomes nor membrane-bound neurosecretory granules were seen. Using fluorescence in-situ hybridization probes for chromosomes 1, 2, 6, 10, 13, 17 and 21, the tumors revealed massive loss of tested chromosomes typical for conventional CRCC. Monosomy of chromosomes 1, 2, 6, 10, 13 and 21 was found in 100, 36, 91, 82, 82, 82 and 64% of cases, respectively. None of the cases showed mutation of exons 9, 11, 13 and 17 of the c-kit gene. The important feature of pigmented microcystic chromophobe renal cell carcinoma is a relatively benign biological behavior and the absence of distant metastases and sarcomatoid transformation.

C-kit expression in renal oncocytomas and chromophobe renal cell carcinomas

C- kit encodes the membrane-bound tyrosine kinase KIT, whose expression has been identified in several types of human neoplasms. Recently, KIT has been reported to be a marker for chromophobe renal cell carcinoma (RCC) and renal angiomyolipoma. However, expression of this molecule has not been adequately studied in other renal tumors, particularly oncocytoma, which may morphologically resemble chromophobe RCC. In this study, we analyzed c- kit messenger RNA (mRNA) levels in 17 chromophobe RCCs and 20 renal oncocytomas obtained from complementary DNA (cDNA) microarrays. Furthermore, comprehensive immunohistochemical analysis of KIT protein using a monoclonal antibody was performed in 226 renal tumors including chromophobe RCC (n=40), oncocytoma (n=41), clear-cell RCC (n=40), renal angiomyolipoma (n=29), and papillary RCC (n=21) on tissue microarrays (TMAs) and was compared with immunostaining results from 25 chromophobe RCCs and 30 oncocytomas using standard sections. The staining intensity was semiquantitatively graded on a 3-tier scoring system. All chromophobe RCCs and oncocytomas showed significant overexpression of c- kit mRNA. The average increase of mRNA compared with normal kidney tissue was 7.4-fold for chromophobe RCCs and 7.4-fold for oncocytomas. Immunohistochemical expression of KIT was found in most chromophobe RCCs (95% in TMAs and 96% in conventional sections) and oncocytomas (88% in TMAs and 100% in conventional sections) but was infrequently observed in renal angiomyolipomas (17%), papillary RCCs (5%), and clear-cell RCCs (3%). Furthermore, the average KIT immunoreactivity in TMAs was stronger in chromophobe RCC (1.93) and oncocytoma (2.07) than in other subtypes of renal tumors tested, including angiomyolipomas (0.17), papillary RCCs (0.05), and clear-cell RCCs (0.03). In conclusion, we found a significant elevation of c- kit mRNA by cDNA expression microarrays and overexpression of KIT protein by immunohistochemistry not only in chromophobe RCCs but also in oncocytomas. In contrast, immunohistochemical expression of KIT was not detected in most other types of renal cell tumors evaluated. The differential expression of c- kit in these renal tumors may have diagnostic and therapeutic implications.