Renal chromophobe cell carcinoma: limitations of paraffin-embedded tissue

Ancillary diagnostic techniques in the evaluation of adult epithelial renal neoplasms: indications, caveats, and pitfalls

The role played currently by the different ancillary diagnostic techniques in the diagnosis of adult epithelial renal tumors continues to be debated. It has also become clear that in some instances light microscopic appearance alone cannot be used to classify these neoplasms into specific categories with the degree of precision required for therapeutic purposes. Renal cell carcinoma (RCC) subtypes may share common histologic characteristics but exhibit different biological behavior and response to therapy which clearly indicates the crucial role that advanced pathologic speciation plays in the current assessment of these neoplasms. Although immunohistochemistry is widely used for the purpose of categorizing renal tumors because of its widespread availability, the immunoprofiles of the various types of renal neoplasms overlap significantly, making definitive diagnostic determinations difficult and challenging at times. This manuscript will address how ancillary diagnostic techniques can be incorporated into the routine evaluation of neoplastic renal masses to improve classification. Both cytology and surgical specimens will be addressed, as fine needle aspiration (FNA) is being used with preference in many cases in the diagnosis of renal masses. Surgical and cytopathologists must intelligently select the ancillary diagnostic technique/s that will provide the information needed to solve the differential diagnosis under consideration in a given case. However, in some cases >1 of these techniques should be used to make an accurate diagnosis with the aim of arriving at an unequivocal diagnosis. The identification of specific signaling pathways that are defective in certain types of renal neoplasms has made possible the design of target-specific therapies that are directed towards the aberrant pathways associated with the defective proteins found in these tumors. This makes the exact classification of these neoplasms and the detection of these aberrant proteins targeted for treatment an absolute requirement for the application of these molecular-based therapeutic interventions. The role that the pathologic assessment plays in the classification of renal tumors becomes more important than ever to take advantage of this and similar new molecular-oriented therapies.

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.

Sporadic hybrid oncocytic/chromophobe tumor of the kidney: a clinicopathologic, histomorphologic, immunohistochemical, ultrastructural, and molecular cytogenetic study of 14 cases

Hybrid oncocytic/chromophobe tumors (HOCT) of the kidney have been described in patients with Birt-Hogg-Dubé syndrome (BHD) and in association with renal oncocytosis without BHD. HOCT in patients without evidence of BHD or renal oncocytosis is exceedingly rare, and these cases have been poorly characterized. We have identified and studied 14 cases of HOCT from previously diagnosed renal oncocytomas (398 cases) and chromophobe renal cell carcinomas (351 cases) without evidence of BHD or renal oncocytosis. Immunohistochemical, ultrastructural, and molecular genetic studies analyzing numerical chromosomal changes, loss of heterozygosity for chromosome 3p, and mutation status of VHL, c-kit, PDGFR, and folliculin (FLCN) genes were performed. HOCTs were identified in nine men and five women (age range 40-79 years). The size of tumors ranged from 2 to 11 cm. All tumors displayed a solid alveolar architecture and were composed of cells with abundant granular eosinophilic oncocytic cytoplasm with perinuclear halos. Occasional binucleated neoplastic cells were present, but irregular, hyperchromatic, wrinkled (raisinoid) nuclei were absent. The cytoplasm contained numerous mitochondria of varying sizes, but only sparse microvesicles with amorphic lamellar content were found. Tumors were positive for CK7 (12/14), AE1-AE3 (14/14), anti-mitochondrial antigen (14/14), E-cadherin (11/13), parvalbumin (12/14), and epithelial membrane antigen (14/14). Tumors were generally negative for racemase, CK20, CD10, and carboanhydrase IX. Interphase fluorescence in situ hybridization revealed multiple chromosomal losses and gains with a median of four (range 1-9) chromosomal aberrations per case. Monosomy of chromosome 20 was common and found in 7 of 14 cases. Monosomy of chromosomes 6 and 9 was present in 4 of 14 cases each, of which two cases displayed monosomy for both chromosomes 6 and 9. Polysomy of chromosomes 10, 21, and 22 was found in 4/14 cases each, of which one case displayed polysomy for all these three chromosomes. No pathogenic mutations were found in the VHL, c-kit, PDGFR, and folliculin (FLCN) genes. (1) We have shown that hybrid oncocytic/chromophobe tumors of the kidney do occur, albeit rarely, outside the Birt-Hogg-Dubé syndrome and without associated renal oncocytosis. (2) These tumors constitute a relatively homogenous group with histomorphologic features of both chromophobe renal cell carcinoma and renal oncocytoma. (3) Sporadic hybrid oncocytic/chromophobe renal tumors are characterized by multiple numerical aberrations (both mono- and polysomies) of chromosomes 1, 2, 6, 9, 10, 13, 17, 21, and 22 and lack of mutations in the VHL, c-kit, PDGFRA, and FLCN genes. (4) The tumors seem to behave indolently as no evidence of malignant behavior was documented in our series, although admittedly, the follow-up was too short to fully elucidate the biological nature of this rare neoplasm. At worst, these tumors could have a low malignant potential, which only can be found out with longer follow-up.

Expression of vitamin D3 receptor in kidney tumors

The kidney is not only a primary vitamin D target organ but also is a key site of vitamin D metabolism. Recent studies have shown that vitamin D has important physiologic effects on proliferation and differentiation in a variety of benign and malignant cells. Our preliminary immunohistochemical study showed that vitamin D receptor (VDR) was highly expressed in renal distal tubules and collecting ducts, whereas the renal proximal tubules and glomeruli did not express VDR. These observations led us to study the expression of VDR in various kidney tumors to determine the possible diagnostic utility of VDR. Paraffin tissue microarray (TMA) blocks were constructed containing core cylinders from clear cell (52), papillary (35), chromophobe (20), sarcomatoid (20), and metastatic (59) renal cell carcinomas (RCCs). Oncocytomas (20), normal adult kidneys (12), and normal adult adrenals (6) were also included. In addition, 30 clear cell RCCs and 3 collecting duct carcinomas were also studied using conventional sections. Furthermore, VDR messenger RNA and protein expression was also quantified using real-time reverse transcriptase-polymerase chain reaction and Western blot analysis. Vitamin D receptor was strongly positive in collecting duct carcinomas (100% [3/3], cytoplasmic), papillary RCCs (94% [33/35], cytoplasmic), chromophobe RCCs (85% [17/20], membranous), and oncocytomas (90% [18/20], cytoplasmic with perinuclear accentuation). In contrast, VDR expression was focal/weak and present only in the peripheral regions of clear cell RCCs. Vitamin D receptor was weakly positive in sarcomatoid variant RCCs (88% [14/16]) regardless of the type of associated original RCC. Overall, VDR is a discriminative marker for renal cell tumors. The preferential expression of VDR in chromophobe RCCs, oncocytomas, and collecting duct carcinomas is in agreement with the concept that these tumors differentiate toward epithelium lining the distal convoluted tubules and collecting ducts. Considering the different VDR expression patterns, VDR is a useful ancillary tool in distinguishing chromophobe RCCs from oncocytomas. In addition, the focal and much weaker VDR expression in clear cell RCCs makes VDR valuable in distinguishing clear cell RCC from other types of RCCs.

Can renal oncocytoma be differentiated from its renal mimics? The utility of anti-mitochondrial, caveolin 1, CD63 and cytokeratin 14 antibodies in the differential diagnosis

Among the epithelial renal tumours with eosinophilic cytoplasm, the main differential diagnostic problem arises between renal oncocytomas (ROs) and eosinophilic variants of chromophobe renal cell carcinomas (RCCs). We investigated the possible role of anti-mitochondrial (AMA), anti-caveolin 1 (CAV1), anti-CD63 (CD63) and anti-cytokeratin 14 (CK14) antibodies in the differential diagnosis of eosinophilic epithelial tumours and applied the Muller and Mowry modification of Hale's colloidal iron stain (HCI). Thirty-five ROs and 77 eosinophilic RCCs (27 chromophobe, 28 clear cell and 22 papillary RCCs) were included in this study. Apical and/or polar CD63 immunostaining (94%) and diffuse AMA (91%) and CAV1 (88%) immunostainings were the characteristics of ROs, whereas diffuse CD63 immunostaining (96%) and diffuse-peripheral AMA (96%) and CAV1 (92%) immunostainings were characteristic immunohistochemical features of eosinophilic chromophobe RCCs. We showed CK14 antibody not to be useful in the differential diagnosis of the eosinophilic epithelial renal tumours. The staining localisations with AMA, CAV1 and CD63 antibodies were significantly different between tumour groups. AMA had 96% sensitivity and 94% specificity, whereas CAV1 had 92% sensitivity and 97% specificity in diagnosing chromophobe RCCs. With HCI staining, ROs, showing apical and/or polar staining, could be differentiated from chromophobe RCCs, showing diffuse cytoplasmic staining. HCI had fairly low (69%) sensitivity and 100% specificity, whereas CD63 had 95% sensitivity and 100% specificity to diagnose ROs. We recommend using CD63 as the best marker of choice for distinguishing ROs from eosinophilic chromophobe RCCs when standard diagnostic criteria are not helpful.

Gene signatures of progression and metastasis in renal cell cancer

PURPOSE

To address the progression, metastasis, and clinical heterogeneity of renal cell cancer (RCC).

EXPERIMENTAL DESIGN

Transcriptional profiling with oligonucleotide microarrays (22,283 genes) was done on 49 RCC tumors, 20 non-RCC renal tumors, and 23 normal kidney samples. Samples were clustered based on gene expression profiles and specific gene sets for each renal tumor type were identified. Gene expression was correlated to disease progression and a metastasis gene signature was derived.

RESULTS

Gene signatures were identified for each tumor type with 100% accuracy. Differentially expressed genes during early tumor formation and tumor progression to metastatic RCC were found. Subsets of these genes code for secreted proteins and membrane receptors and are both potential therapeutic or diagnostic targets. A gene pattern ("metastatic signature") derived from primary tumor was very accurate in classifying tumors with and without metastases at the time of surgery. A previously described "global" metastatic signature derived by another group from various non-RCC tumors was validated in RCC.

CONCLUSION

Unlike previous studies, we describe highly accurate and externally validated gene signatures for RCC subtypes and other renal tumors. Interestingly, the gene expression of primary tumors provides us information about the metastatic status in the respective patients and has the potential, if prospectively validated, to enrich the armamentarium of diagnostic tests in RCC. We validated in RCC, for the first time, a previously described metastatic signature and further showed the feasibility of applying a gene signature across different microarray platforms. Transcriptional profiling allows a better appreciation of the molecular and clinical heterogeneity in RCC.

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.

Chromophobe renal cell carcinoma: a comparative study of histological, immunohistochemical and ultrastructural features using high throughput tissue microarray

AIMS

In some cases distinction between chromophobe renal cell carcinoma (CRCC), oncocytoma and clear cell (conventional) renal cell carcinoma (eosinophilic variant) using routine light microscopy remains problematic. The present study investigates the level of agreement in the diagnosis of CRCC, as well as the histological features most frequently used for this diagnosis by two pathologists with a special interest in renal neoplasia. The sensitivity and specificity of immunohistochemical markers in cases with overlapping histological features in the diagnosis of CRCC were also studied. Electron microscopy was performed, as a diagnostic gold standard, on all of the cases.

METHODS AND RESULTS

Thirty-two renal tumours with predominantly eosinophilic cytoplasm were reviewed in a blinded fashion by two pathologists. The diagnosis and morphological features used to render each diagnosis were tabulated. Validation of the utility of keratin 7 and 20, epithelial membrane antigen (EMA), vimentin, CD10, parvalbumin, RCC antigen, antimitochondrial antibody and Hale's colloidal iron was performed by the construction of a tissue microarray (TMA) master block. Based on histological criteria alone, overall agreement on the diagnosis of these tumours was reached in 69% of the cases, while there was total disagreement in 12%. In 59% of the cases, total agreement was reached in classifying the case as a CRCC based on histology alone. Kappa statistics for interobserver variability were calculated as only slight agreement (kappa = 0.3). The histological features most frequently associated with a diagnosis of CRCC were accentuated cell borders (87%) and a combination of hyperchromatic wrinkled nuclei (79%) and perinuclear halos (74%). The most sensitive and specific marker for CRCC was parvalbumin (sensitivity 0.91; specificity 1.0). The immunohistochemical profile of EMA+/ vimentin- was useful but had low specificity (sensitivity 0.75; specificity 0.4). CD10 had the highest sensitivity (1.0) but worst specificity (0.25) for CRCC. Keratin 7 had high sensitivity (0.83) but fairly low specificity (0.37) for CRCC. Hale's colloidal iron and the RCC antigen marker were not contributory. Finally, the antimitochondrial antibody was found to be fairly sensitive (0.83) for excluding CRCC.

CONCLUSIONS

A small but significant proportion of renal tumours with cells having eosinophilic cytoplasm cannot be classified, even by experienced pathologists, based on histology alone. In these cases it is imperative to use markers with known sensitivity and specificity for the diagnosis of CRCC.

Renal oncocytoma with prominent intracytoplasmic vacuoles of mitochondrial origin

AIMS

We observed two oncocytomas with prominent intracytoplasmatic vacuoles. To investigate if this previously undescribed finding is a diagnostic feature and compatible with the diagnosis of oncocytoma, we characterized these vacuoles by electron microscopy and immunohistochemistry.

METHODS AND RESULTS

The tumours were analysed by transmission electron microscopy. Immunohistochemistry was performed with antimitochondrial antibody, anti-Golgi-zone antibody, anti-lysozyme antibody and anti-human-trans-Golgi-network antibody. By electron microscopy, the vacuoles were found to be double-membrane-bounded, and some contained fragmented christae. Immunohistochemistry showed a positive reaction of the vacuoles with anti-mitochondrial antibody. Staining with anti-Golgi-zone antibody, anti-lysozyme antibody and anti-human-trans-Golgi-network antibody was negative.

CONCLUSION

Both tumours are benign oncocytomas. The phenomena of cells with prominent intracytoplasmatic vacuoles is not inconsistent with the diagnosis of oncocytoma. The vacuoles are of mitochondrial origin and may develop, by balloon degeneration, as a mechanism of mitochondrial involution and elimination.

Chromophobe renal cell carcinoma: clinicopathological study of 7 cases

Chromophobe renal cell carcinoma (CRCC) may be grossly and microscopically confused with oncocytoma. It is now believed that many, if not all, of the so-called malignant oncocytomas or oncocytomas with metastases reported in the literature were indeed chromophobe renal cell carcinomas. CRCC is characteristically positive for colloidal iron and shows cytoplasmic microvesicles in electron microscopy. This study of CRCC is thought to be the first one done in Latin America. Of a total of 106 renal epithelial neoplasms, 7 (6.6%) fulfilled the criteria for chromophobe renal cell carcinoma. This frequency in Brazil is similar to that in other parts of the world. There was no difference in age, sex, and race distribution of CRCC compared to usual renal epithelial tumors. Grossly, the CRCC ranged in size from 3.5 to 20 cm (average: 10.2 cm) in greatest dimension. Most frequently, the tumor was brown on the cut surface. The growth pattern showed compact areas in all tumors and, in most of the cases, both clear and eosinophilic cellular subtypes were seen. The electron microscopic findings favor an origin of the microvesicles from outpouchings of the outer membrane of mitochondria. The strong positivity for colloidal iron in spite of the destruction of the cytoplasmic vesicles in paraffin-embedded specimens seems to indicate that the acid mucopolysaccharides are not located inside the microvesicles. By the time of diagnosis, only one case had regional lymph node metastases and this particular case was the only one mixed (associated with the usual renal cell carcinoma). The follow-up examination after nephrectomy showed that prognosis seems to be favorable in CRCC, except when the tumor coexists with the usual renal cell carcinoma.

Antimitochondrial antibody (113-1) in the differential diagnosis of granular renal cell tumors

Abundant granular eosinophilic cytoplasm is a common feature of renal oncocytoma, chromophobe renal cell carcinoma, eosinophilic variant of papillary renal cell carcinoma, and the granular variant of clear cell renal cell carcinoma (RCC). Each of these entities has a unique architectural pattern and a distinctive molecular or cytogenetic profile. The chief reason for their distinction from one another is the difference in their biologic behavior. Careful and thorough light microscopic examination distinguishes most cases based on individual characteristic architectural and cytomorphologic features. However, precise characterization may be difficult in some cases because of overlapping morphologic features. We evaluated the antimitochondrial antibody 113-1 in an attempt to ascertain differences in immunostaining patterns in 57 cases of granular renal tumors, including 20 renal oncocytomas, 15 chromophobe RCCs, 13 granular variants of clear cell RCC, and nine eosinophilic variants of papillary RCC. Distinctive, and nearly exclusive, staining patterns were observed among the groups, with chromophobe RCC showing peripheral accentuation of coarse cytoplasmic granules (15 of 15), renal oncocytoma with diffuse and fine granularity (20 of 20), and granular variant of clear cell RCC with irregular cytoplasmic distribution of coarse granules (11 of 13). Staining was most intense in the eosinophilic variant of papillary RCC and was generally coarsely granular and diffuse. Staining patterns also differed in clear cell areas within chromophobe RCC and the granular variant of clear cell RCC. Although clear cells in the former group showed granular staining with peripheral accentuation, most of the clear cells in the latter lacked any staining. We conclude that, in addition to distinct cytoarchitectural features, immunostaining patterns with antimitochondrial antibody 113-1 appear to be a useful discriminatory adjunct in the complex differential diagnosis of granular renal cell tumors.

The role of ultrastructural pathology in the diagnosis of epithelial and unusual renal tumors

The electron microscopic and immunohistochemical features of epithelial and unusual renal tumors are reviewed. Ultrastructural and immunohistochemical features of diagnostic value are highlighted. An attempt is made to address histogenesis/differentiation issues that would help in understanding morphologic findings, with an emphasis placed on the role that ultrastructural evaluation has played in demonstrating these.

Chromophobe cell renal carcinoma: clinicopathological features of 50 cases

PURPOSE

We review the clinicopathological features of chromophobe cell renal carcinoma.

MATERIALS AND METHODS

Cases were identified by reviewing the histology of all renal neoplasms resected between 1977 and 1990. Clinical data were obtained by chart review.

RESULTS

Of 50 cases a majority (53%) were discovered incidentally and most (86%) were stage I. Typical pathological findings included the presence of 2 cell types (pale and eosinophilic), reactivity for Hale's colloidal iron, ultrastructural cytoplasmic vesicles and deoxyribonucleic acid aneuploidy. At last followup 47 patients (94%) were tumor-free or dead of unrelated causes. Survival was similar in patients with clear cell carcinoma of similar grade and stage.

CONCLUSIONS

Chromophobe cell carcinoma is a morphologically distinctive neoplasm with a favorable prognosis. Distinction from renal oncocytoma is important.