Hanlin L. Wang

Immunohistochemical distinction between primary adenocarcinoma of the bladder and secondary colorectal adenocarcinoma.

Primary adenocarcinoma of the urinary bladder sometimes causes a diagnostic dilemma because it can be indistinguishable morphologically from adenocarcinoma of colorectal origin secondarily involving the bladder by metastasis or direct extension. It is much less well studied than conventional urothelial carcinoma and colorectal adenocarcinoma because of its rarity. The current study was specifically designed to investigate whether an important mechanism involved in the pathogenesis of colorectal adenocarcinoma, &bgr;-catenin dysregulation, was also important for the development of primary bladder adenocarcinoma and whether these two morphologically similar tumors could be distinguished immunohistochemically. Formalin-fixed, paraffin-embedded tissues from 17 primary adenocarcinomas of the urinary bladder, 16 colorectal adenocarcinomas involving the bladder, and 10 conventional urothelial (transitional) carcinomas were included in this study. Thirteen of the primary bladder adenocarcinomas were moderately to well differentiated (enteric type) and morphologically indistinguishable from colorectal cancers. The remaining four primary tumors were poorly differentiated (two cases) or of clear cell type (two cases). Immunohistochemical studies using a panel of monoclonal antibodies demonstrated positive nuclear staining for &bgr;-catenin expression in 13 of the 16 (81%) colorectal adenocarcinomas secondarily involving the bladder but in none of the primary adenocarcinomas or the urothelial carcinomas. Instead, positive membranous (and some cytoplasmic) staining was present in all primary bladder tumors with the exception of two poorly differentiated adenocarcinomas where no &bgr;-catenin staining was detected. All secondary colorectal adenocarcinomas stained negatively for CK7 and thrombomodulin (TM), whereas positivity for CK20 was observed in 15 (94%) cases. All urothelial carcinomas stained positively for CK7 and TM, and four of them also for CK20. Primary adenocarcinomas of the bladder showed mixed staining patterns for CK7, CK20, and TM with a positive rate of 65%, 53%, and 59%, respectively. These data indicate that dysregulation of &bgr;-catenin, an important aberration seen in colorectal carcinogenesis, does not appear to play a role in the pathogenesis of the bladder adenocarcinoma. In addition, our data demonstrate that a panel of immunostains, including CK7, CK20, TM, and &bgr;-catenin, is of diagnostic value in differentiating primary bladder adenocarcinoma from secondary adenocarcinoma of colorectal origin.

Lymphovascular Invasion in Colorectal Cancer: An Interobserver Variability Study

Background Lymphovascular invasion (LVI) in colorectal cancer (CRC) is considered a strong stage-independent prognostic factor and influences decisions regarding adjuvant chemotherapy in patients with stage II tumors. However, the degree of interobserver agreement among pathologists for LVI in CRC is largely unknown. This study was undertaken to examine such interobserver variability, and we hypothesized that the use of immunohistochemical markers for vascular and lymphatic channels could improve interobserver agreement. Design Fifty cases of American Joint Committee on Cancer stage II moderately differentiated CRC from 1990 to 2005 from the pathology archives were selected; mucinous, medullary, and other recognized special subtypes were excluded. Fifty hematoxylin and eosin (H&E) slides (1 from each case) were circulated to 6 gastrointestinal pathologists, who independently assessed small and large vessel invasion. No diagnostic guidelines were given to the participating pathologists; each was instructed to apply the criteria for LVI that he or she used in daily practice. Immunohistochemistry (IHC) for D2-40 and CD31 was performed on corresponding paraffin blocks. The IHC slides were randomized, recirculated, and rescored for LVI. Results were analyzed by kappa (κ) statistics, which correct for agreement by chance, and for percentage agreement. Results The average κ values were determined for the H&E slides (large and small vessel), CD31 (small vessel), and D2-40 (small vessel) (Fig. 1). Agreement was fair for H&E small vessel invasion [κ=0.28; 95% confidence interval (CI): 0.22-0.34]. The least agreement was seen in interpretation of H&E large vessel invasion (κ=0.18; 95%CI: 0.11-0.26). Agreement was not improved by use of immunohistochemical stains: CD31 (large vessel, κ=0.42, 95%CI: 0.20-0.63, small vessel, κ=0.26, 95%CI: 0.10-0.42) and D2-40 (κ=0.32, 95%CI: 0.21-0.42). Conclusions Interobserver variability in diagnosis of LVI was substantial on H&E slides and did not improve upon use of IHC. Agreement in evaluation of large vessel invasion was only slightly higher than would be seen by chance alone. This study highlights the need for criteria in evaluation of LVI, as this assessment may impact patient prognosis and thus change the course of clinical treatment.

Value of CDX2, villin, and α -methylacyl coenzyme A racemase immunostains in the distinction between primary adenocarcinoma of the bladder and secondary colorectal adenocarcinoma

Primary adenocarcinoma of the urinary bladder is an uncommon neoplasm that can be indistinguishable morphologically from colorectal adenocarcinoma secondarily involving the bladder by direct extension or metastasis. In the current study, 17 enteric-type primary adenocarcinomas of the bladder were immunohistochemically examined for the expression of CDX2, villin and α-methylacyl coenzyme A racemase (AMACR), immunomarkers preferentially expressed in colorectal adenocarcinoma. For comparison, 17 secondary colorectal adenocarcinomas involving the bladder, 23 primary colorectal adenocarcinomas and 14 conventional urothelial carcinomas were similarly studied. The results show that all 40 (100%) colorectal adenocarcinomas expressed CDX2 and 39 (98%) expressed villin. The expression of these two immunomarkers was less frequent in primary bladder adenocarcinomas, observed in eight (47%) and 11 (65%) cases, respectively (P<0.0001 and P=0.0019, respectively). The frequency of positive AMACR immunostaining was similar between these two types of tumors, detected in 28 (70%) colorectal adenocarcinomas and 11 (65%) primary bladder adenocarcinomas (P=0.694). None of the urothelial carcinomas exhibited CDX2 or villin immunoreactivity; and only two (14%) showed positive staining for AMACR. These results demonstrate that CDX2 and villin are of diagnostic value in aiding in the distinction between primary adenocarcinoma of the bladder and secondary colorectal carcinoma. Lack of CDX2 and villin signals points strongly to a bladder primary.

Glypican-3 as a Useful Diagnostic Marker That Distinguishes Hepatocellular Carcinoma From Benign Hepatocellular Mass Lesions

CONTEXT Histopathologic distinction between hepatocellular carcinoma (HCC) and benign hepatocellular mass lesions, particularly hepatocellular adenoma, can sometimes be challenging. The currently available ancillary tools are suboptimal in terms of sensitivity and specificity. OBJECTIVE To further characterize the diagnostic value of glypican-3 (GPC3), a cell surface proteoglycan that has recently been shown to be overexpressed in HCC, in the distinction between HCC and benign hepatocellular mass lesions. DESIGN A total of 221 surgically resected liver specimens were subjected to immunohistochemical staining using a monoclonal antibody specific for GPC3. These included 111 HCCs, 48 hepatocellular adenomas, 30 focal nodular hyperplasias, and 32 large regenerative nodules in the background of cirrhosis. RESULTS Cytoplasmic, membranous, and canalicular staining for GPC3 was detected in 84 (75.7%) of the 111 HCCs, among which, 61 (72.6%) of the 84 cases exhibited diffuse immunoreactivity. In contrast, none of the 110 cases of hepatocellular adenoma, focal nodular hyperplasia, and large regenerative nodule showed detectable GPC3 staining. Focal GPC3 immunoreactivity was detected in cirrhotic nodules in 11 (16.4%) of 67 HCC cases with a cirrhotic background, but no background staining was observed in the remaining 44 HCCs without cirrhosis. GPC3 expression in HCCs did not correlate with the size, differentiation, or stage of the tumors; the presence or absence of cirrhotic background; or the underlying etiologies. CONCLUSIONS GPC3 is a specific immunomarker for HCC that can be used to distinguish HCC from benign hepatocellular mass lesions, particularly hepatocellular adenoma. However, the diagnosis of HCC should not rely entirely on positive GPC3 immunostaining because focal immunoreactivity can be detected in a small subset of cirrhotic nodules. In addition, GPC3 expression in HCC can also be focal, and thus, the lack of GPC3 staining does not exclude the diagnosis of HCC.

Elevated protein expression of cyclin D1 and Fra-1 but decreased expression of c-Myc in human colorectal adenocarcinomas overexpressing β-catenin

Mutations of the adenomatous polyposis coli tumor suppressor gene, or its downstream target β‐catenin, have been implicated in the initiation of most sporadic human colorectal epithelial neoplasms. These mutations, in turn, lead to aberrant nuclear accumulation of β‐catenin and subsequent activation of the β‐catenin/Tcf transcription factor complex. In vitro studies utilizing cultured human colon cancer cell lines have identified c‐myc, cyclin D1 and fra‐1 as target genes of β‐catenin/Tcf signaling. In our study, 12 cases of human colorectal adenocarcinomas were examined by Western immunoblotting analysis and immunohistochemical staining to specifically investigate whether the protein expression of these target genes was indeed altered in vivo by β‐catenin dysregulation. The results show that the protein level of β‐catenin was significantly increased in all 12 tumors (3.4 ± 1.0‐fold increase compared to the control normal mucosa by Western immunoblotting, p < 0.05), and this increase was associated with positive nuclear staining by immunohistochemistry in 10 cases. Increased levels of expression of cyclin D1 and Fra‐1 proteins were also demonstrated in every tumor (9.0 ± 2.7 and 3.3 ± 0.9‐fold increases compared to normal mucosa, respectively). Surprisingly, the protein level of c‐Myc was significantly decreased in all tumors examined by 49 ± 19% (p < 0.05), but the c‐myc mRNA level was increased in 8 of 12 tumors when compared to that in normal mucosa by RT‐PCR. Immunohistochemical staining performed on these carcinomas and additional 27 colorectal carcinomas further demonstrated that the protein expression level of c‐Myc and β‐catenin nuclear localization were not correlated. Moreover, 15 of 20 colorectal adenomas exhibited positive nuclear β‐catenin immunostaining, among which 11 also exhibited increased c‐Myc protein expression. These data thus support the notion that upregulation of cyclin D1 and Fra‐1 in human colorectal adenocarcinomas is driven by abnormally expressed β‐catenin. However, the regulation of c‐myc expression in colorectal tumors appears to be more complex. While dysregulated β‐catenin may cause a transcriptional upregulation of the c‐myc gene, the c‐Myc protein expression appears to be further regulated by a posttranscriptional mechanism(s) during the process of neoplastic progression.

cDNA Arrays and Immunohistochemistry Identification of CD10/CALLA Expression in Hepatocellular Carcinoma

The histological diagnosis of hepatocellular carcinoma (HCC) can be complicated by difficulty in differentiation from cholangiocarcinoma and metastatic carcinoma. Immunohistochemical stains currently in use are suboptimal in terms of specificity and sensitivity. Using cDNA array analysis for differential gene expression, we demonstrated a significant increase in mRNA expression level of CD10/CALLA, a type 2 cell-surface metalloproteinase, in HCC, which was subsequently confirmed by reverse transcriptase-polymerase chain reaction and Western blotting analysis. To test the possibility of using CD10/CALLA as a diagnostic marker for HCC, various intrahepatic tumors were studied immunohistochemically using a monoclonal antibody for CD10. A characteristic canalicular-staining pattern was observed in normal hepatocytes and at the apical surface of bile duct epithelial cells. The canalicular expression of CD10 was identified in 9 of 15 HCCs examined (60%), whereas 10 cholangiocarcinomas and 8 of 9 metastatic carcinomas lacked this staining. In three of the six HCCs negative for CD10, the surrounding nonneoplastic liver tissue was also negative, suggesting fixation-associated loss of immunoreactivity. Six HCCs had stronger CD10 staining in tumor cells when compared to the surrounding nonneoplastic tissue. Three cases of benign bile duct adenomas also expressed CD10 at the luminal aspect. One of the MCs showed a diffuse, cytoplasmic staining for CD10, a pattern readily distinguishable from that of HCC. A panel of other immunohistochemical markers were also studied for comparison, including polyclonal anti-carcinoembryonic antigen, cytokeratin (CK) 7, CK20, and alpha-fetoprotein. Our results demonstrate that cDNA arrays can be effectively used to identify new diagnostic markers, and that CD10 is a reliable marker for identifying HCC, particularly when used in conjunction with a panel of immunohistochemical markers (polyclonal anti-carcinoembryonic antigen, CK7, CK20, and alpha-fetoprotein) and in the distinction from cholangiocarcinoma.

KRAS Mutation Testing in Human Cancers: The Pathologist's Role in the Era of Personalized Medicine

A number of studies have shown that although antiepidermal growth factor receptor (EGFR) monoclonal antibodies are effective treatments for metastatic colorectal cancer (mCRC), only patients with wild-type KRAS tumors derive clinical benefit from these therapies. The anti-EGFR monoclonal antibodies panitumumab and cetuximab are approved in the United States for treatment of mCRC refractory to chemotherapy but are not recommended for use in patients with mutations in KRAS codons 12 or 13. Similarly, panitumumab is approved for the treatment of mCRC only in patients with wild-type KRAS in Europe and Canada. It is clear that KRAS mutational analysis will become an important aspect of disease management in patients with mCRC. Consequently, it will be important for pathologists and oncologists to develop and agree on standardized KRAS testing and reporting procedures to ensure optimum patient care. Pathologists will be central to this process because of their crucial role in selecting appropriate tumor specimens for testing, choosing the molecular diagnostic laboratory to be used, assisting in the selection of a suitable KRAS test, and interpreting the results of KRAS mutational analysis. Guidelines for KRAS testing that address these and other important points of consideration have recently been proposed in the United States and the European Union.

Expression of epidermal growth factor receptor in squamous cell carcinomas of the anal canal is independent of gene amplification

Immunohistochemical detection of expression of the epidermal growth factor receptor (EGFR) has been utilized to identify eligible patients with solid malignant tumors, including colorectal adenocarcinoma, for monoclonal antibody therapy (eg, cetuximab). The EGFR status in squamous cell carcinoma of the anal canal, an uncommon malignancy traditionally treated with chemoradiation, has not been well investigated. In this study, 38 primary squamous cell carcinomas of the anal canal were immunohistochemically examined for EGFR expression and analyzed by fluorescence in situ hybridization (FISH) for EGFR gene copy numbers. The results showed a variable degree of EGFR expression in 21 (55%) tumors, among which 13 (62%) cases exhibited a 2+ to 3+ staining pattern according to the Dako EGFR phamDx interpretation guide. There were no significant differences among tumors stratified by stage, degree of keratinization, or tissue block storage times. FISH analysis showed that none of the 34 cases with interpretable results had EGFR gene amplification. Increased gene copy numbers due to polysomy 7 were seen in seven of 18 (39%) cases that expressed EGFR protein and four of 16 (25%) cases that did not (P=0.3876). Ten (56%) tumors with positive EGFR staining showed a balanced disomy 7 pattern and one case with monosomy 7 exhibited strong EGFR expression (3+). These results demonstrate that EGFR is overexpressed in more than one-half of the squamous cell carcinomas of the anal canal through mechanisms other than gene amplification. These observations may have important therapeutic implications since EGFR-based targeted therapies have shown promise for other malignant neoplasms.

Expression of alpha-methylacyl-coenzyme A racemase in nephrogenic adenoma.

Nephrogenic adenoma is a benign lesion composed of small glandular structures that develops along the urothelium with uncertain pathogenesis. Some investigators believe that nephrogenic adenoma develops by a metaplastic process in response to injury to the urothelium, while others believe that it arises from detached renal tubules. Nephrogenic adenoma may be present in the prostatic urethra and morphologically mimic prostatic adenocarcinoma. Alpha-methylacyl-coenzyme A racemase (AMACR), a recently identified prostate cancer marker, is typically negative in normal urothelium and prostatic glands, and positive in distal convoluted renal tubules in addition to prostatic adenocarcinomas. Therefore, evaluation of AMACR expression in nephrogenic adenoma will have significance in the pathologic diagnosis and in understanding pathogenesis of this lesion. We studied 38 nephrogenic adenomas by clinical, histologic, and immunohistochemical analyses for AMACR (P504S) and high molecular weight cytokeratin (34βE12). Twenty-two of 38 nephrogenic adenomas (58%) demonstrated strong cytoplasmic positivity for AMACR, ranging from patchy, focal to diffuse staining. In addition, 16 of 26 (62%) nephrogenic adenomas were negative for 34βE12. To our knowledge, this is one of the first report of a completely benign lesion, which can be found in the prostate, showing strong AMACR immunoreactivity. Our findings suggest using caution when interpreting positive AMACR immunostaining in prostatic specimens. These findings could be explained by possible renal tubular origin or renal differentiation, at least in a subset, of nephrogenic adenomas.

Human kidney injury molecule-1 (hKIM-1): a useful immunohistochemical marker for diagnosing renal cell carcinoma and ovarian clear cell carcinoma.

Human kidney injury molecule-1 (hKIM-1), a type I transmembrane glycoprotein expressed in injured renal proximal tubules, was also found in renal cell carcinoma (RCC). The current study attempts to evaluate the diagnostic utility of hKIM-1 in a large series of 480 neoplasms including defined subtypes of renal cell tumors, metastatic RCCs, and nonrenal tumors. Tissue microarray (TMA) sections containing 179 renal cell tumors (73 clear cell RCC, 30 papillary RCC, 16 chromophobe RCC, 15 oncocytoma, and 45 metastatic RCC) were included in this study. In addition, 80 cases of renal cell neoplasm and 221 nonrenal tumors in routine tissue sections were also included. Both TMA and routine sections were incubated with anti-hKIM-1 monoclonal antibody using an EnVision-HRP kit. The results demonstrated that a membranous/cytoplasmic staining pattern for hKIM-1 was observed in 54 of 73 (74%) clear cell RCCs and 28 of 30 (93%) papillary RCCs on TMA sections. Zero of 54 chromophobe RCCs and 4 of 41 (9.75%) oncocytomas were positive for hKIM-1 when combining TMA and routine sections. Similar staining results were observed in 35 of 45 (78%) metastatic RCCs. Data from cDNA microarray expression and Western blot demonstrated similar findings. Fifteen of 16 cases (93.8%) of clear cell carcinoma of the ovary demonstrated positive reactivity for hKIM-1. These data indicate that hKIM-1: (1) is a relatively sensitive and specific marker for papillary, clear cell, and metastatic RCCs, (2) can be used to distinguish clear cell from chromophobe RCC, and (3) may serve as a diagnostic marker for clear cell carcinoma of the ovary.