Small oncocytic papillary renal cell carcinoma in diabetic glomerulosclerosis

Histologic and immunohistochemical features of oncocytic papillary renal cell carcinoma (RCC) have not been fully elucidated. The author herein report a case of oncocytic papillary RCC (OPRCC). A 71-year-old man with diabetes mellitus and diabetic nephropathy was found to have a small right renal tumor by CT. He had been treated with hemodialysis for chronic renal failure for 10 years. A nephrectomy was performed. Grossly, a small (1.5cm) encapsulated yellow tumor was found in the kidney. Histologically, the tumor was completely encapsulated, and consisted entirely of atypical oncocytes arranged in a diffuse papillary structure with fibrovascular cores. The oncocytes showed grade 3 atypia and pseudostratification. A few mitotic figures were seen, and psammoma bodies, foamy macrophages, and hemosiderin were scattered. Histochemically, the tumor cells were positive for colloidal iron, and negative for mucins (Alcian blue/PAS). Immunohistochemical results of the tumor were as follows: α-methylacyl-coenzyme A rasemase (AMACR) +++, vimentin +++, cytokeratin (CK) 18 +++, CD10 +++, S-100 protein +, MUC1 ++, MUC2 ++, MUC5AC ++, MUC6 ++, panCK Cam5.2 +, CK7 +, CK8 +, CK14 +, CK19 +, CK20 +, p53 +, HepPar1 +, CD68 +, platelet-derived growth factor-α (PDGFRA) +, PanCK AE1/3 -, PanCK WSS -, PanCK MNF115 -, CK 35BE12 -, CK5/6 -, EMA -, desmin -, smooth muscle antigen -, α-fetoprotein -, CEA -, estrogen receptor -, progesterone receptor -, HER2 -, p63 -, and KIT -. Ki67 labeling was 6%. These results suggest that OPRCC can express colloidal iron, low molecular weight CKs, S100 protein, MUC1, MUC2, MUC5AC, MUC6, p53, PDGFRA, and HepPar1.     

Multifocal metanephric adenoma in childhood

Metanephric adenoma is the most commonly occurring member of the metanephric tumor family, which also includes metanephric adenofibroma and metanephric stromal tumor. According to the World Health Organization classification, however, it is not commonly multifocal. Reported herein is the case of a 9-year-old boy with multifocal metanephric adenoma. Histologically, surgical sections showed multifocal proliferation of small rounded and uniform cells with smooth nuclear contours, scant pale-staining cytoplasm, dark-staining nuclei, and inconspicuous nucleoli: the cells were arranged in sheets and acinal, ductal, glomeruloid, and papillary structures. On immunohistochemistry the tumor cells were positive for vimentin, cytokeratins (CAM5.2, AE1/AE3, and CK18), and WT1, but negative for cytokeratin 7 (CK7) and epithelial membrane antigen (EMA). The Ki-67 labeling index was <1%. In addition, cytogenetic analysis indicated a normal karyotype (46XY). Other histologically similar tumors are papillary renal cell carcinoma and nephroblastoma, and it is necessary to distinguish metanephric adenoma from those tumors because of malignancy. In contrast to those tumors, metanephric adenoma has inconspicuous nucleoli, loss of CK7 and EMA expression, and no mitotic figures. Thus, the histological and immunohistochemical features of the present case were compatible with metanephric adenoma.     

p63, CK7, PAX8 and INI-1: an optimal immunohistochemical panel to distinguish poorly differentiated urothelial cell carcinoma from high-grade tumours of the renal collecting system

Carvalho J C, Thomas D G, McHugh J B, Shah R B & Kunju L P
(2012) Histopathology  60, 597–608
p63, CK7, PAX8 and INI‐1: an optimal immunohistochemical panel to distinguish poorly differentiated urothelial cell carcinoma from high‐grade tumours of the renal collecting system Aims: High‐grade, poorly differentiated, infiltrative carcinomas involving the renal sinus region often pose challenging differential diagnostic considerations, specifically differentiation of urothelial carcinoma (UC) from renal cell carcinoma (RCC) subtypes. Accurate classification, especially the distinction of UC from RCC, is critical, as therapeutic approaches differ. Methods and results: Cluster analysis was performed on immunohistochemical data from 18 invasive UCs, six CDCs, two RMCs, 18 type 2 papillary renal cell carcinomas (PRCCs) and 20 high‐grade clear cell renal cell carcinomas (CRCCs) using a broad panel of traditional and novel immunohistochemical markers. The initial analysis with all antibodies segregates almost all the RCCs (45 of 46, 98%) from all the UCs based on the lack of expression of p63 in all (100%) RCCs, along with predominant strong expression of paired box gene 8 (PAX8) and vimentin, predominant lack of expression of high molecular weight cytokeratin (HMCK) and CK7 and variable expression of RCC, CD10, CA1X and PAX2. All the UCs cluster together with strong, diffuse reactivity for p63, predominant reactivity for CK7 and high molecular weight kininogen (HMWK), and absent to minimal staining with PAX8, RCC antigen, PAX2, alpha‐methylacyl‐CoA racemase (AMACR), carbonic anhydrase IX (CAIX) and vimentin. After removing antibodies with significant overlap and/or minimal impact, a second analysis with a limited panel including p63, CK7, vimentin, integrase interactor 1 (INI‐1) and PAX8 was performed. Again, the majority of UCs cluster into one group and p63 positivity separates all UCs from RCCs. Conclusions: Lack of INI‐1 expression, noted exclusively in RMCs, segregates RMCs into a separate cluster. PAX8 is rarely positive (17%) in UC, is commonly expressed in CDC, RMC, PRCC and CRCC and is superior to PAX2.     

Wide spectrum screening keratin as a marker of metaplastic spindle cell carcinoma of the breast: an immunohistochemical study of 24 patients

Wide spectrum screening keratin as a marker of metaplastic spindle cell carcinoma of the breast: an immunohistochemical study of 24 patients
Aims : Metaplastic spindle cell carcinomas may be difficult to distinguish histologically from other spindle cell lesions in the breast. Variable staining with cytokeratin immunomarkers has been reported for metaplastic carcinomas. We evaluated the diagnostic utility of anti-cytokeratin polyclonal antibody, wide spectrum screening keratin, to assess spindle cell breast lesions.
Methods and results : Twenty-four patients with spindle cell breast carcinoma and 31 patients with benign or malignant spindle cell tumours were studied using a panel of antibodies directed against multiple cytokeratins (AE1/AE3, CAM5.2, wide spectrum screening keratin), epithelial membrane antigen (EMA), and vimentin. Sites of origin for the 31 controls included breast, bone, and soft tissue. All but one (95.8%) metaplastic carcinomas stained positively with wide spectrum screening keratin. Only rare or focal immunoreactivity was observed with AE1/AE3 in four cases; however, sensitivity of AE1/AE3 was improved in 13 cases using steam EDTA as an antigen retrieval technique. Three cases were immunoreactive with CAM5.2 and eight cases were immunoreactive with EMA. All control cases lacked immunoreactivity with the cytokeratin panel and EMA. The spindle cells in the metaplastic breast tumours (88%) and in the controls (97%) stained with vimentin.
Conclusions : Wide spectrum screening keratin may be the most useful and convenient antibody in differentiating metaplastic spindle cell carcinoma from other spindle cell lesions in the breast.     

Differentiation markers in pancreatic head adenocarcinomas: MUC1 and MUC4 expression indicates poor prognosis in pancreatobiliary differentiated tumours

Aims:  To examine how accurately immunohistochemical markers discriminate between pancreatobiliary and intestinal-type adenocarcinomas in the pancreatic head and to explore the prognostic importance of these markers among each of these histological types.
Methods and results:  Histopathological features of 114 consecutively resected adenocarcinomas of pancreatobiliary ( n  = 67) and intestinal ( n  = 47) type of differentiation were recorded according to a standardized protocol. Immunohistochemistry for cytokeratin (CK) 7, CK20, MUC1, MUC2, MUC4 and CDX2 was performed on tissue microarrays. Classification of the adenocarcinomas based on immunohistochemistry was compared with the morphological evaluation of histological type. Presence of CK7 and MUC4, and absence of CDX2, were independent predictors of pancreatobiliary versus intestinal type. Using these markers to optimize immunohistochemical classification, agreement between immunohistochemical and morphological classification was only moderate (κ = 0.53). In pancreatobiliary differentiated tumours, MUC1 and/or MUC4 expression was an independent prognostic factor (hazard ratio 2.02, 95% confidence interval 1.02, 3.98) when adjusting for nodal involvement, vessel involvement and tumour size. In intestinally differentiated tumours, none of the markers was significantly associated with prognosis.
Conclusions:  Agreement between immunohistochemical and morphological classification of pancreatic head adenocarcinomas is moderate. In pancreatobiliary adenocarcinomas, MUC1 and/or MUC4 expression indicates a particularly poor prognosis.     

肾细胞癌的临床病理与免疫表型研究

目的 研究肾细胞癌的临床病理特征、预后及免疫表型特点.方法 复习114例肾细胞癌的临床病理资料、HE切片,按2004年WHO肾肿瘤分类标准重新分类、随访并进行免疫组织化学染色.结果 114例.肾细胞癌包括5个类型,肾透明细胞癌77例(67.5%)、乳头状肾癌11例(9.6%)、肾嫌色细胞癌14例(12.3%)、Xp11.2易位_/TFE3基因融合相关性肾癌10例(8.8%)、未能分类肾肿瘤2例(1.8%).免疫组织化学结果,肾透明细胞癌主要表达CK(93.5%,72/77)、CD10(93.5%,72/77)、波形蛋白(75.3%,58/77),乳头状肾癌主要表达α-甲酰基辅酶A消旋酶(AMACR,11/11),肾嫌色细胞癌主要表达CD117(11/14),Xp11.2易位/TFE3基因融合相关性肾癌TFE3、AMACR、CD10和CK的阳性率分别为10/10、10/10、9/10和7/10.结论 肾癌是一组形态学上各有特征的异质性肿瘤,在形态学基础上,CD10、波形蛋白、CD117、AMACR、CK7、TFE3有助于亚型的诊断.     

Alpha-methylacyl-CoA racemase as a marker in the differential diagnosis of metanephric adenoma.

Metanephric adenoma (MA), a well-described renal neoplasm, usually behaves in a benign fashion. It may have areas that are morphologically similar to papillary renal cell carcinoma (RCC) type, or epithelial (tubular predominant) type Wilms' tumor. Prior immunohistochemical studies of MA have reported variable staining patterns. Alpha-methylacyl-CoA racemase (AMACR), a molecular marker for prostate carcinoma, has subsequently been found to be overexpressed in breast, colorectal and ovarian cancers, among others. Recent microarray analysis of renal tumors has shown an increase of AMACR mRNA levels in papillary RCC but not in other subtypes. We investigated the utility of immunohistochemical staining for AMACR, cytokeratin 7(CK7), CD57 and WT1 to differentiate between the above-mentioned three neoplasms. Immunohistochemical stains were performed on paraffin-embedded tissue sections from 25 papillary RCC, 10 MAs and eight Wilms' tumors. AMACR was positive in one (10%) of 10 MAs and 24 (96%) of 25 papillary RCC, while it was negative in all Wilms' tumors. CK7 was positive in 20 of 25 papillary RCCs, focally positive in one Wilms' tumor and was negative in all MAs. CD57 was positive in all six MAs that were stained, focally positive in one of 25 papillary RCC and one of eight Wilms' tumors. WT1 was positive in seven of 10 MAs, three of 25 papillary RCCs and all eight Wilms' tumors. In conclusion, diffuse and strong immunoreactivity for AMACR may be useful in differentiating papillary RCC from MA but a panel which includes AMACR, CK7 and CD57 is better in this differential diagnosis. AMACR is not helpful in differentiating MA from Wilms' tumor, but CD57 is helpful in this differential diagnosis. WT1 may be useful in separating Wilms' tumor from MA and papillary RCC but is not helpful in differentiating MA from papillary RCC.     

A renal cell carcinoma with components of both chromophobe and papillary carcinoma

We report a case of a morphologically unusual renal cell carcinoma with features of both chromophobe and papillary carcinoma. Immunohistochemical analysis of high molecular weight cytokeratins (HMWCK), cytokeratin 7 (CK7), cytokeratin 19 (CK19), c-Kit, and α-methylacyl-CoA racemase (AMACR) demonstrated differential profiles for the two components of the tumor, consistent with the respective patterns commonly observed for pure chromophobe and papillary renal cell carcinomas. Specifically, the chromophobe tumor cells expressed CK7 and c-Kit weakly, while HMWCK, CK19, and AMACR were not detectable. In contrast, the papillary tumor cells expressed uniformly HMWCK, CK7, and c-Kit and focally CK19 and AMACR. Fluorescence in situ hybridization analysis of nuclei isolated from paraffin-embedded tumor tissue detected monosomy 1, disomy 7, and monosomy 17, a common and characteristic finding in chromophobe carcinomas, in a majority of, but not all tumor cells, whereas a population characterized by disomy 1, trisomy 7, and trisomy 17, a frequent finding in papillary carcinoma, was not identifiable. Electron microscopic analysis revealed numerous characteristic small cytoplasmic vesicles in the chromophobe areas, which were absent in the papillary component. This case illustrates the rare coexistence of two distinct and admixed histologic types of renal cell carcinoma.     

Recent advances of immunohistochemistry for diagnosis of renal tumors

The recent classification of renal tumors has been proposed according to genetic characteristics as well as morphological difference. In this review, we summarize the immunohistochemical characteristics of each entity of renal tumors. Regarding translocation renal cell carcinoma (RCC), TFE3, TFEB and ALK protein expression is crucial in establishing the diagnosis of Xp11.2 RCC, renal carcinoma with t(6;11)(p21;q12), and renal carcinoma with ALK rearrangement, respectively. In dialysis‐related RCC, neoplastic cells of acquired cystic disease‐associated RCC are positive for alpha‐methylacyl‐CoA racemase (AMACR), but negative for cytokeratin (CK) 7, whereas clear cell papillary RCC shows the inverse pattern. The diffuse positivity for carbonic anhydrase 9 (CA9) is diagnostic for clear cell RCC. Co‐expression of CK7 and CA9 is characteristic of multilocular cystic RCC. CK7 and AMACR are excellent markers for papillary RCC and mucinous tubular and spindle cell carcinoma. CD82 and epithelial‐related antigen (MOC31) may be helpful in the distinction between chromophobe RCC and renal oncocytoma. WT1 and CD57 highlights the diagnosis of metanephric adenoma. The combined panel of PAX2 and PAX8 may be useful in the diagnosis of metastatic RCC.     

Abundant expression of AMACR in many distinct tumour types

AIMS: Alpha-methylacyl-CoA racemase (AMACR), a mitochondrial and peroxisomal enzyme, is a valuable tool to confirm the diagnosis of prostate cancer, especially if combined with basal cell markers. To extend this diagnostic utility to other neoplasias, we comprehensively surveyed AMACR expression in human tumours. METHODS: We performed immunohistochemical analyses on tissue microarrays of AMACR expression in over 125 different human tumour types and 80 normal tissues. RESULTS: Microarray analysis revealed that tumours with prominent AMACR expression included adenocarcinomas of the prostate (72%), hepatocellular carcinomas (77%), papillary renal cell carcinomas (70%), and colorectal adenocarcinomas (71%). AMACR expression was equally frequent in colorectal adenomas and carcinomas. No significant difference in AMACR expression between untreated and hormone-refractory prostate cancers was observed. In the thyroid, AMACR expression was found in 42% of the follicular carcinomas but in only 16% of follicular adenomas. However, a more detailed analysis on a thyroid tissue microarray did not confirm a significant difference of AMACR expression in follicular adenoma and carcinomas. CONCLUSION: Taken together, the results indicate that AMACR is expressed in a wide variety of adenocarcinomas, and its diagnostic utility is restricted to specific areas.     

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

Carvalho J C, Wasco M J, Kunju L P, Thomas D G & Shah R B
(2011) Histopathology 58, 169–179 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.     

Sporadic clear cell renal cell carcinoma with diffuse cytokeratin 7 immunoreactivity

AIMS: Clear cell renal cell carcinoma (CRCC) with diffuse immunoreactivity for CK7 is described. METHODS: All cases of CRCC, measuring 20 mm or less in diameter over a period of 10 years, were examined. Areas of regenerative epithelial cell nests (REC) were also examined. RESULTS: Fifteen specimens containing 29 nodules were diagnosed as CRCC due to the characteristic clear cytoplasm. Of these 29 nodules, 21 showed diffuse CK7 positivity while eight showed CK7 negativity. The CK7 positive CRCC measured less than 16 mm and contained varying proportions of tumour cells with chromophil cytoplasm. Architecturally, CK7 positive CRCC consisted of cysts and solid cell nests with tubulo-acinar formations or papillary formations. Immunostaining for AMACR, CD10 and RCC showed negative or focal reactivity in the CK7 positive CRCC, frequently positive reactivity in CK7 negative CRCC and negative reactivity in REC which also displayed strong CK7 reactivity. The ten patients with 21 CK7 positive CRCC developed no metastatic disease over a follow up time that ranged from 1 to 10 years (mean of 3 years). CONCLUSIONS: CRCC characterised by diffuse CK7 positivity represents a distinct type of CRCC with characteristic histopathological and immunohistochemical features.     

Alpha-methyl CoA racemase expression in renal cell carcinomas

Alpha-methyl CoA racemase (AMACR), a new molecular marker for prostate cancer, has been recently reported to be one of the most highly expressed genes in papillary renal cell carcinomas (RCCs). We tested the diagnostic usefulness of AMACR antibody in a series of 110 renal tumors: 53 papillary RCCs (33 type 1, 20 type 2); 25 conventional RCCs; 6 chromophobe RCCs; 9 oncocytomas; 5 mucinous tubular and spindle tumors; 2 urothelial carcinomas; 7 angiomyolipomas; and 2 Bellini carcinomas. Immunohistochemical staining was performed on formalin-fixed, paraffin-embedded tissue sections, with a primary prediluted rabbit monoclonal anti-AMACR antibody. Both type 1 and type 2 papillary RCCs exhibited cytoplasmic immunoreactivity for AMACR, with diffuse strong granular staining in 96.4% (53/55) of tumors, without correlation with type or nuclear grade. The 5 mucinous, tubular, and spindle cell carcinomas strongly expressed AMACR, and only 5 of 25 clear cell RCCs and 1 of 9 oncocytomas were focally reactive. The remaining 6 chromophobe RCCs, 5 urothelial carcinomas, and Bellini duct carcinomas showed no immunoreactivity for AMACR. Because high expression of AMACR is found in papillary RCCs (type 1 and 2) and in mucinous, tubular, and spindle cell carcinomas of the kidney, immunostaining for AMACR should be used in conjunction with other markers when histological typing of a renal tumor is difficult.     

An immunohistochemical study of primary signet-ring cell carcinoma of the stomach and colorectum: I. cytokeratin profile in 42 cases

Expression of cytokeratin (CK) profiles in primary signet-ring cell carcinoma (SRCC) of the stomach and colorectum have rarely reported; only two such studies are present in the world literature. Herein, an immunohistochemical study on cytokeratin (CK) expression was performed in 42 cases of primary SRCC of the stomach (30 cases) and colorectum (12 cases). SRCC was defined as an adenocarcinoma in which more than 50% adenocarcinoma cells showed SRCC phenotype with prominent intracytoplasmic mucins. In the gastric SRCC, the expression of CK was as follows; CK AE1/3 (30/30, 100%) CK CAM5.2 (30/30, 100%), CK 34BE12 (0/30, 0%), CK5/6 (2/30, 7%), CK7 (26/30, 89%), CK8 (12/30, 40%), CK14 (0/30, 0%), CK18 (30/30, 100%), CK19 (2/30, 7%), and CK20 (3/30, 10%). In the colorectal SRCC, the expression of CK was as follows; CK AE1/3 (12/12, 100%) CK CAM5.2 (12/12, 100%), CK 34BE12 (0/12, 0%), CK5/6 (0/12, 10%), CK7 (2/12, 17%), CK8 (3/12, 25%), CK14 (0/12, 0%), CK18 (12/12, 100%), CK19 (7/12, 58%), and CK20 (8/12, 67%). A statistical analysis showed that significant differences of CK expression between the gastric SRCC and colorectal SRCC were observed in CK7 (stomach 67% vs. colorectum 17%), CK19 (7% vs. 42%) and CK20 (13% vs. 67%); gastric SRCC tended to express CK7, but not CK19 and CK20, while colorectal SRCC tended to express CK19 and CK20, but not CK7. In gastric SRCC, CK7+/CK20- pattern was as follows: CK7+/CK20- (24/30, 81%), CK7+/CK20+ (2/30, 6%), CK7-/CK20+ (1/30, 3%), and CK7-/CK20- (3/30, 10%). CK7/CK19 patterns in gastric SRCC were as follows; CK7+/CK19- (25/30, 83%) CK7+/CK19+ (1/30, 3%), CK7-/CK19+ (1/30, 3%), CK7-/CK19- (3/30, 10%). In colorectal SRCC, the CK7/CK20 patterns were as follows: CK7+/CK20- (2/12, 17%), CK7+/CK20+ (0/12, 0%), CK7-/CK20+ (8/12, 66%), and CK7-/CK20- (2/12, 17%). The CK7/CK19 pattern in colorectal SRCC was as follows; CK7+/CK19- (1/12, 8%), CK7+/CK19+ (1/12, 8%), CK7-/CK19+ (6/12, 50%), and CK7-/CK19- (4/12, 34%). Statistical data indicated that CK7+/CK20- and CK7+/CK19- patterns were significantly prevalent in gastric SRCC, and CK7-/CK20+, CK7-/CK19+ and CK7-/CK20- patterns dominated significantly in colorectal SRCC. CK expression has been studied largely in terms of CD7/CK20 expression pattern in various carcinomas. The present study provided possible usefulness of CK7/19 expression status in various carcinomas including SRCC.     

Biphasic squamoid alveolar renal carcinoma with positive CD57 expression: A clinicopathologic study of three cases

Biphasic squamoid alveolar renal cell carcinoma (BSARCC) is a rare and recently characterized form of papillary renal cell carcinoma (PRCC). Herein, we describe three cases of BSARCC that were CD57+. Among a total of 90 cases of PRCC, three cases were found to be consistent with a diagnosis of BSARCC. In addition to reviewing these cases, we reviewed the relevant literature pertaining to this form of cancer and assessed the immunohistochemical staining for CD57 on the available tumor samples. The three BSARCC cases in the present study were composed of two primary populations of cells. Tumors stained positive for CK, PAX8, CK7, CK19, AMACR, EMA, and vimentin. Larger cells expressed detectable levels of cyclin D1, and expression of CD57 was limited to the larger cells. All three patients were alive and free of disease during the most recent follow‐up. Our results suggest that the CD57 positivity of at least a subset of cases should necessitate their differentiation from cases of metanephric adenoma.     

Expression of alpha-methylacyl-CoA racemase (P504s) in various malignant neoplasms and normal tissues: astudy of 761 cases

Alpha-methylacyl CoA racemase (AMACR), also known as P504S, plays an important role in peroxisomal beta-oxidation of branched-chain fatty acids. It has recently been shown that AMACR is highly expressed in prostate cancer and that it may be an important diagnostic marker for prostate carcinoma. However, little is known about expression of AMACR in normal tissues and other malignant tumors. In this study, we investigated expression of AMACR in 539 malignant tumors and 222 normal human tissues of various types by immunohistochemical analysis. mRNA levels of AMACR in normal organs and in selected tumors were assessed by real time PCR. In normal tissue, high expression of AMACR mRNA was identified in liver, kidney and salivary gland, while AMACR protein was detected in liver (hepatocytes), kidney (tubular epithelial cells), lung (only bronchial epithelial cells), and gallbladder (only mucosal epithelial cells). High expression of AMACR mRNA was found in prostate, liver, and kidney cancers but rarely in stomach and bladder cancers. A high percent of adenocarcinomas arising from these organs express AMACR, including 17 of 21 (81%) of hepatocellular carcinomas and 18 of 24 (75%) of renal cell carcinomas. In addition, carcinomas arising from tissues normally not expressing AMACR were also positive for the antigen, including 17 of 18 (94%) prostate carcinomas, 9 of 29 (31%) of urothelial carcinomas, and 4 of 15 (27%) of gastric adenocarcinomas. Two hundred and fifty cases of adenocarcinomas from lung, breast, pancreas, bile duct, adrenal gland, salivary gland, ovary, thyroid and endometrium were negative or rarely positive for AMACR. Neuroendocrine carcinomas rarely expressed AMACR. Melanomas, squamous cell carcinomas, basal cell carcinomas, soft tissue tumors (including epithelioid sarcomas and synovial sarcoma), thymomas, and germ cell tumors were negative for AMACR. Our data provide important baseline information for using AMACR in clinical practice and also are valuable in furthering understanding of the pathogenic role of AMACR in malignant neoplasms.     

Squamous cell carcinoma originated from an epidermal cyst

Epidermal cyst (EC) of the skin is a very common condition. Squamous cell carcinoma (SCC) very infrequently arises from EC. A 76-year-old Japanese woman was admitted to our hospital because of multiple papules in the nose and nasal cavity. The clinical diagnosis was sebaceous hyperplasia. An excisional biopsy was obtained from one papule. Histologically, the papule showed an EC. The EC communicated with the epidermis. Islands of atypical cells with hyperchromatic nuclei and infrequent pearl formation were recognized around and adjacent to EC. No connections were seen between the atypical cell islands and epidermis. The atypical cells had hyperchromatic nuclei and nucleoli. Mitotic figures and keratinous pearls were scattered. The HE diagnosis was probable SCC probably arising from EC. Immunohistochemically, the atypical cells were positive for pancytokeratin AE1/3, cytokeratin (CK) 5/6, CK14, CK18, CK 34BE14, EMA, p53, Ki-67 (labeling 90%), and p63. They were negative for pancytokeratin CAM5.2, CK7, CK8, CK19, CK20, vimentin, S100 protein, HMB45, synaptophysin, and CD56. CD68 was positive in histiocytes and giant cells in the foreign body reaction. The EC showed the same immunoprofile as the SCC, except for negative p53 and low Ki-67 labeling in the EC. The histological and immunohistochemical diagnosis was definite SCC arising from EC.     

Useful immunohistochemical panel for differentiating clear cell papillary renal cell carcinoma from its mimics

Clear cell papillary renal cell carcinoma (CCPRCC) is a recently described low-grade renal cell tumor. In this study, we investigated the expression of paired box 8 (PAX-8), carbonic anhydrase IX (CA IX), CK7, and α-methylacyl-CoA-racemase (AMACR) in this tumor by immunohistochemistry in a group of 20 cases of CCPRCC. Clear cell papillary renal cell carcinoma showed diffuse (70%) or intermediate (30%) nuclear positivity for PAX-8 in each case, with predominantly moderate intensity (50%). Ninety percent of the cases showed some degree of cytoplasmic staining for CA IX, predominantly with moderate intensity (50%). In addition, each case of CCPRCC also showed diffuse membranous staining for CK7. Most CCPRCCs (95%) were negative for AMACR. PAX-8, CA IX, CK7, and AMACR comprise a concise panel for distinguishing CCPRCC from its mimics. PAX-8 positivity helps to confirm the renal origin of this tumor. Positivity for CA IX and CK7 differentiate CCPRCC from conventional clear cell renal cell carcinoma, which is usually CA IX positive while CK7 negative. The CK7-positive and AMACR-negative pattern seen in CCPRCC differentiates it from papillary renal cell carcinoma, which is usually positive for both AMACR and CK7.     

Biphasic alveolosquamoid renal carcinoma: a histomorphological,immunohistochemical, molecular genetic,and ultrastructural study of a distinctive morphologic variant of renal cell carcinoma

Only a few cases of sarcomatoid renal cell carcinomas (RCCs) with squamous differentiation have been published. We present 2 RCCs exhibiting a hitherto not reported biphasic neoplastic cell population exhibiting a predominantly alveolar architecture where squamoid differentiation was identified in one of the neoplastic cell populations. None of the tumors showed chromophobe features or any evidence of sarcomatoid transformation. The tumors arose in 2 adult patients and were characterized by routine histology, immunohistochemistry, ultrastructure, array comparative genomic hybridization, confirmatory fluorescent in situ hybridization, and loss of heterozygosity analysis. Tumors measured 3 and 4 cm and were located within the renal parenchyma and had no pelvicalyceal connection. Both tumors were composed of a distinctly dual-cell population. The larger tumor cells displayed squamoid features and formed round well-demarcated solid alveolated islands that, in large parts, were surrounded by a smaller neoplastic cell component. The squamoid cells were immunoreactive for cytokeratins (CKs) (AE1-AE3, Cam 5.2, CK5/6, CK7, and CK20), epithelial membrane antigen, racemase/AMACR, and carboanhydrase IX (in 1 case focally). The small cell population was positive for CK7, epithelial membrane antigen, and racemase/AMACR, whereas CK20, AE1-3, and carboanhydrase IX were negative. CD10 was focally positive in the large squamoid cells in 1 case. Cathepsin K, E-cadherin, and CD117 displayed focal positivity in 1 case. Vimentin, RCC marker, parvalbumin, S100 protein, S100 A1, p63, p53, CDX2, uroplakin III, HMB45, TFE3, WT1, synaptophysin, chromogranin A, thyroglobulin, and TTF1 were negative. The proliferative activity (Ki-67) was low (1%) in the small cell component in both cases, whereas the large neoplastic tumor cells displayed a significantly higher proliferation (20%-35%). Ultrastructurally, desmosomes and tonofilaments were identified in the large tumor cells, confirming squamoid differentiation in a subset of tumor cells. Array comparative genomic hybridization of 1 analyzable case (confirmed with fluorescent in situ hybridization and loss of heterozygosity analysis) revealed partial or complete losses of chromosomes 2, 5, 6, 9, 12, 15, 16, 17, 18 and 22, (including biallelic loss of CDKN2A locus) and partial gains of chromosomes 1, 5, 11, 12 and 13. Follow-up at 6 years showed no recurrence or metastasis in 1 patient. The other (male) patients had a subcutaneous metastasis at presentation, but during a 1-year follow-up no evidence of recurrence or further metastatic events have been documented. Our data indicate that biphasic alveolosquamoid renal carcinoma is a unique and distinctive tumor. The large squamoid and small tumor cells have overlapping but still distinctive immunohistochemical patterns of protein expression. Multiple chromosomal aberrations were identified, some of them located in regions with known tumor suppressor genes and oncogenes.