Targeting the NTRK Fusion Gene in Pancreatic Acinar Cell Carcinoma: A Case Report and Review of the Literature.

Pancreatic acinar cell carcinoma (PACC) is a rare pancreatic exocrine malignancy. Compared with the more common pancreatic ductal adenocarcinoma (PDAC), PACC is more common in younger White men, has earlier stages and a lower mean age (56 vs 70 years) at the time of presentation, and has a better prognosis. In addition to differences in demographic, histologic, and clinical characteristics, PACC has a genomic profile distinct from PDAC, with only rare mutations in TP53, KRAS, and p16 that are commonly found in PDAC. This case report presents a man aged 81 years who presented with a pancreatic body mass with peripancreatic lymph node enlargement. Biopsy of the mass showed acinar cell carcinoma. The patient underwent upfront surgical resection, followed by one cycle of adjuvant gemcitabine, with stoppage of therapy due to poor tolerance. Lower-dose gemcitabine was reintroduced after disease progression 6 months later. Nab-paclitaxel was added to gemcitabine after 6 cycles because of a continued increase in the size of peripancreatic lymph nodes. Combination chemotherapy was stopped after 4 cycles because of further disease progression with new liver metastasis. Molecular testing showed the presence of an SEL1L-NTRK1 fusion. Targeted therapy was started with the oral neurotrophic tropomyosin receptor kinase (NTRK) inhibitor larotrectinib at a dosage of 100 mg twice daily. At the time of writing, the patient has been on therapy for 13 months with an exceptional radiographic response and has not experienced any grade 3 adverse effects. To our knowledge, this is the first clinical report of an NTRK gene fusion in a patient with PACC. This case study highlights the significance of tumor molecular profiling in patients with pancreatic tumors, especially rare histologies.

Treatment recommendations to cancer patients in the context of FDA guidance for next generation sequencing.

BACKGROUND: Regulatory approval of next generation sequencing (NGS) by the FDA is advancing the use of genomic-based precision medicine for the therapeutic management of cancer as standard care. Recent FDA guidance for the classification of genomic variants based on clinical evidence to aid clinicians in understanding the actionability of identified variants provided by comprehensive NGS panels has also been set forth. In this retrospective analysis, we interpreted and applied the FDA variant classification guidance to comprehensive NGS testing performed for advanced cancer patients and assessed oncologist agreement with NGS test treatment recommendations. METHODS: NGS comprehensive genomic profiling was performed in a CLIA certified lab (657 completed tests for 646 patients treated at Roswell Park Comprehensive Cancer Center) between June 2016 and June 2017. Physician treatment recommendations made within 120 days post-test were gathered from tested patients' medical records and classified as targeted therapy, precision medicine clinical trial, immunotherapy, hormonal therapy, chemotherapy/radiation, surgery, transplant, or non-therapeutic (hospice, surveillance, or palliative care). Agreement between NGS test report targeted therapy recommendations based on the FDA variant classification and physician targeted therapy treatment recommendations were evaluated. RESULTS: Excluding variants contraindicating targeted therapy (i.e., KRAS or NRAS mutations), at least one variant with FDA level 1 companion diagnostic supporting evidence as the most actionable was identified in 14% of tests, with physicians most frequently recommending targeted therapy (48%) for patients with these results. This stands in contrast to physicians recommending targeted therapy based on test results with FDA level 2 (practice guideline) or FDA level 3 (clinical trial or off label) evidence as the most actionable result (11 and 4%, respectively). CONCLUSIONS: We found an appropriate "dose-response" relationship between the strength of clinical evidence supporting biomarker-directed targeted therapy based on application of FDA guidance for NGS test variant classification, and subsequent treatment recommendations made by treating physicians. In view of recent changes at FDA, it is paramount to define regulatory grounds and medical policy coverage for NGS testing based on this guidance.

Primary intraplacental gestational choriocarcinoma: histologic and genetic analyses.

Gestational choriocarcinoma is a highly malignant form of gestational trophoblastic tumors. Placental involvement of the tumor is exceedingly rare. We describe a case of intraplacental choriocarcinoma in a full-term placenta. Microscopically, there were sheets of highly pleomorphic trophoblasts invading the placenta, leaving isolated chorionic villi within the tumor. We utilized molecular genetic methods to determine the genotype of the tumor and compared it with that of the placenta. Short tandem repeat polymorphism analysis was performed on tumor and placental DNA macrodissected from unstained slides of formalin-fixed, paraffin-embedded tissue. The assay included polymerase chain reaction reactions of 10 polymorphic genetic loci. Comparing the polymorphic genetic markers of the tumor with the placenta revealed a complete match in the genotype of all loci examined. The results suggest that the choriocarcinoma originated from the current placenta sharing exactly the same genotype of multiple polymorphic markers. It also excludes a nongestational choriocarcinoma, which is of germ cell origin.

Therapeutic Banding for Bleeding Duodenal Lymphangiectasias: A Novel Approach.

With endoscopic advancements, the number of detected intestinal lymphangiectasias has been on the rise. They are generally considered benign and incidental; occasionally, these lesions carry complications, and best management options need to be established. Bleeding intestinal lymphangiectasias should be considered a rare cause in the differential diagnosis for gastrointestinal bleeding. References in the literature primarily indicate surgical treatment in these situations. In this study, we report an uncommon case of a man with esophageal adenocarcinoma who developed acute gastrointestinal bleeding from duodenal lymphangiectasias that were successfully banded.

Generation of cDC-like cells from human induced pluripotent stem cells via Notch signaling.

BACKGROUND: Dendritic cells (DCs) play critical roles in regulating the innate and adaptive immune responses, and have long been a major focus of cancer immunotherapy. Accumulating evidence suggests that conventional type 1 DCs (cDC1s) excel in cross-presentation of exogenous antigens on MHC-I molecules and induction of antitumor CD8+ T cell immunity; however, obtaining large numbers of cDC1s is difficult. The use of reprogramming and differentiation technology is advantageous for obtaining unlimited numbers of autologous cDC1s especially for therapeutic interventions where repeated vaccinations are required. However, generation of cDC1s from human induced pluripotent stem cells (iPSCs) remains elusive. METHODS: Human iPSCs established from peripheral blood T cells and monocytes were differentiated to myeloid cells under on-feeder or feeder-free culture conditions in vitro. Phenotype, genomic and transcriptomic signature, and function of human iPSC-derived DCs were analyzed. The role of Notch signaling for the generation of HLA-DR+ cells from human iPSCs was interrogated by a loss- and gain-of-function approach. RESULTS: Flow cytometric analyses and single-cell profiling of HLA-DR+ cells revealed that human iPSCs gave rise to CD141+XCR1+CLEC9A+ cells (cDC1s), CLEC4AhiCLEC10A-CD1c+ cells (cDC2As), CLEC4AloCLEC10A+CD1c+ cells (cDC2Bs), CD163-CD5+CD1c+ cells (CD5+cDC2s), and AXL+SIGLEC6+ cells (AS-DCs) on OP9 feeder cells expressing the Notch ligand delta-like 1 (OP9-DL1) while the majority of iPSC-derived cells differentiated on OP9 cells were CD163+CD5-CD1c+ cells (DC3s) and monocytes. Plasmacytoid DCs were not differentiated from iPSCs on either OP9 or OP9-DL1 cells. Inhibition of Notch signaling during co-culture of iPSC-derived CD34+ hematopoietic progenitor cells with OP9-DL1 cells abrogated generation of cDC1s, cDC2As, cDC2Bs, CD5+cDC2s, and AS-DCs but increased frequency of DC3s. Notch-activated human iPSC-derived XCR1+CLEC9A+HLA-DR+CD11c+ cells exhibited similar gene expression profile with peripheral blood cDC1s. Human iPSC-derived DCs have phagocytic, T-cell proliferative, and cytokine-producing functions. CONCLUSIONS: Our study demonstrates a critical role of Notch signaling in regulating developmental pathway of human cDCs. These findings provide insights into the future development of personalized treatment with unlimited numbers of autologous cDCs from human iPSCs.

Breast carcinoma with amplified HER2: a gene expression signature specific for trastuzumab resistance and poor prognosis.

Recent trials have shown remarkable efficacy from combined trastuzumab and chemotherapy in the adjuvant setting of breast cancer. In spite of these successes, refractory breast cancer has emerged as a clinically problematic outcome for a subset of patients managed this way. In an effort to clarify and optimize the treatment regimens for breast cancer patients who are candidates to receive trastuzumab, we sought to analyze whether a distinctive genetic signature could be characterized that would reliably predict the treatment outcome. The ability to predict who will respond and who will become refractory to this agent will allow for improved, rational clinical management of these patients and further stratify the personalized nature of this treatment regimen. In this study, 41 consecutive cases of breast carcinoma with well-documented amplification of the human epidermal growth factor receptor-2 gene and corresponding banked fresh-frozen tissue were identified and divided into two separate groups based on whether they received trastuzumab or not. The first group consisted of 12 patients who had received trastuzumab in the adjuvant setting, of which three later experienced tumor recurrence. The second group consisted of 10 patients not treated with trastuzumab, of which 6 were later found to have recurrence. Differentially expressed genetic profiles were determined using human genome-wide Illumina Bead Microarrays. The differentially expressed genes for non-recurrence vs recurrence in the trastuzumab-treated group were distinct from those in the same comparison group in the untreated group. Differential expression of key genes identified in this study might offer an insight into a possible mechanism of trastuzumab resistance in breast carcinoma, and may emerge as potential predictive biomarkers indicative of trastuzumab resistance.

Use of Fecal Microbial Transplantation for Immune Checkpoint Inhibitor Colitis.

Immune checkpoint inhibitors (ICIs) can result in immune-related adverse events which require rapid identification and treatment. Gastrointestinal immune-related adverse events are among the most frequent and severe of these events. ICI colitis can be refractory to current therapies such as corticosteroids and biologic therapy. Fecal microbiota transplantation (FMT) is currently used in cases of recurrent Clostridioides difficile colitis. Many investigations are underway to test the utility of FMT for additional indications, including inflammatory bowel disease (IBD). We present a 71-year-old man with ICI colitis that was nonresponsive to currently defined management options and treated with benefit from FMT.

Vitamin A deficiency causes metaplasia in vocal fold epithelium: a rat study.

OBJECTIVES: The roles of vitamin A in the vocal fold epithelium are not well documented, although vitamin A has been used as a conservative treatment for laryngeal leukoplakia. The purpose of this study was to analyze the roles of vitamin A in vocal fold epithelial differentiation. METHODS: Vitamin A-deficient (VAD) rats were generated, and the abnormality of their vocal fold epithelium was examined by hematoxylin and eosin staining and immunohistochemical analysis for keratin 10 and transglutaminase (TGase) 1. RESULTS: The VAD experimental rats exhibited orthokeratosis of the vocal fold epithelium. Keratin 10 and TGase 1 were up-regulated in the epithelium of the VAD rats. CONCLUSIONS: It is suggested that vitamin A suppresses TGase 1 expression in normal vocal folds to inhibit keratinization, and that the TGase 1 up-regulation caused by vitamin A deficiency may be related to the formation of metaplasia in the laryngeal epithelium.

Lymphovascular and perineural invasion are associated with poor prognostic features and outcomes in colorectal cancer: A retrospective cohort study.

BACKGROUND: Lymphovascular and perineural invasion (LVI and PNI) are associated with poor outcomes in several cancers. We sought to identify clinical variables associated with LVI and PNI in colorectal cancer (CRC) and to determine their impact on survival. METHODS: A retrospective review was performed of the National Cancer Data Base (NCDB), 2004-2011. Patients with CRC and a documented LVI or PNI status were included. Multivariate analysis was conducted to examine the associations between clinical variables and LVI/PNI, PNI and survival, and LVI/PNI and lymph node (LN) status in patients with T1 and T2 tumors. RESULTS: In total, 158,777 patients were included. LVI status was documented for 139,026 patients, 26.3% of whom were positive. PNI status was documented in 142,034 patients, 11.1% of whom were positive. The multivariable model identified a number of pathologic and clinical characteristics associated with the presence of LVI and PNI, including a number of features of advanced CRC. PNI was independently associated with reduced survival (HR 3.55, 95%CI 1.78-7.09). In T1 or T2 tumors, LVI and PNI were significantly associated with LN involvement. CONCLUSIONS: LVI and PNI are associated with advanced CRC. PNI is an independent poor prognostic marker for survival in CRC. LVI and PNI are associated with LN involvement in T1 and T2 tumors. Documentation of LVI and PNI status on biopsy specimens may help in prognostication and decision-making in the management of these early tumors.

Reappraisal of Serosal Invasion in Patients With T3 Colorectal Cancer by Elastic Stain: Clinicopathologic Study of 139 Surgical Cases With Special Reference to Peritoneal Elastic Lamina Invasion.

CONTEXT: Peritoneal elastic lamina invasion (PELI) has been reported to be an important adverse prognostic factor in pT3 colorectal cancer (CRC). However, the data supporting this contention are limited. OBJECTIVE: To clarify the associations between PELI of pT3 CRC and prognostic significance, 139 consecutive surgical cases of pT3 CRC were examined. DESIGN: One hundred thirty-nine consecutive in-house surgical cases of pT3 CRC between 1993 and 2011 were examined. Thirty consecutive surgical cases of pT4a CRC resected during the same period were examined for comparison. Case selections were restricted to pT3 CRCs with the sections containing the deepest adenocarcinoma invasion partially or entirely covered with the peritoneum. Elastic staining was performed on one section containing the deepest tumor invasion partially or entirely covered with the peritoneum. The associations between the presence of PELI and clinicopathologic factors including prognosis of the patients were examined. RESULTS: Peritoneal elastic lamina invasion was identified in 23.0% (32 of 139) of the pT3 CRCs. PELI was associated with primary site (P = .006), lymph node metastasis (P < .001), lymphovascular invasion (P < .001), recurrence (P = .007), and patient's age (P = .002). The proportions of patients with a 4-year recurrence-free period in those with negative PELI, positive PELI, and pT4a tumor were 90.3%, 66.7%, and 28.9%, respectively (P < .001). CONCLUSIONS: Elastic staining is useful to evaluate the serosal invasion of CRC. Positive PELI is a significant predictive factor for lymph node metastasis and recurrence-free survival in patients with pT3 CRC. This indicates that pT3 tumors with PELI should be treated like pT4a tumors.

Pancreatic hepatoid carcinoma: a rare form of pancreatic neoplasm.

Primary pancreatic hepatoid carcinoma (PHC) is extremely rare, resembling hepatocellular carcinoma (HCC) in terms of morphology and immunohistochemical features. Hepatoid carcinoma can present in other organs, most noticeably in the stomach. PHC is present in two forms either a pure form like HCC or admixed with other histologic tumor components characteristic of the underlying primary site (endocrine tumors, ductal, or acinar adenocarcinomas). Here, we report a 69-year-old male patient with distal pancreatic mass incidentally found during a CT scan workup for a pulmonary nodule suspicious for metastatic prostate adenocarcinoma. We described the clinical, cytological, and histological finding and conducted a literature review.

Role of Repeat 18F-Fluorodeoxyglucose Positron Emission Tomography Examination in Predicting Pathologic Response Following Neoadjuvant Chemoradiotherapy for Esophageal Adenocarcinoma.

IMPORTANCE: Predicting complete pathologic response (CPR) preoperatively can significantly affect surgical decision making. There are conflicting data regarding positron emission tomography computed tomography (PET CT) characteristics and the ability of PET CT to predict pathologic response following neoadjuvant chemoradiotherapy in esophageal adenocarcinoma because most existing studies that include squamous histology have limited numbers and use nonstandardized PET CT imaging. OBJECTIVE: To determine if PET CT characteristics are associated with CPR in patients undergoing trimodality treatment for esophageal adenocarcinoma. DESIGN, SETTING, AND PARTICIPANTS: A retrospective medical record review was conducted at a large tertiary cancer center from a prospectively maintained database from January 1, 2005, to December 31, 2012. Inclusion criteria were patients undergoing esophagectomy for locally advanced esophageal adenocarcinoma post-neoadjuvant chemoradiotherapy with 2 standardized PET CT studies done at our institution (pre-neoadjuvant chemoradiotherapy and post-neoadjuvant chemoradiotherapy) for review. Data collected included clinical, pathologic, imaging, and treatment characteristics. MAIN OUTCOME AND MEASURE: The primary study outcome was the association of PET CT characteristics with histologic confirmed pathologic response. RESULTS: Of the total participants, 77 patients met the inclusion criteria. Twenty-two patients (28.6%) had CPR vs 55 patients (71.4%) who had incomplete pathologic response. The 2 groups were similar in age, sex, race/ethnicity, comorbid conditions, Eastern Cooperative Oncology Group status, tumor grade, chemotherapy, and radiation regimen and days between the 2 PET CTs. The mean prestandardized uptake variable (SUV; 14.5 vs 11.2; P = .05), δ SUV (10.3 vs 5.4; P = .02), and relative δ SUV (0.6 vs 0.4; P = .02) were significantly higher in those with CPR vs incomplete pathologic response. Using the Youden Index, a δ SUV value less than 45% was predictive of residual disease with a positive predictive value of 91.7% (95% CI, 73-99; P < .05). CONCLUSIONS AND RELEVANCE: To our knowledge, this is the largest study examining the role of PET CT characteristics in esophageal adenocarcinoma for patients undergoing neoadjuvant chemoradiotherapy that demonstrates that δ SUV of less than 45% is associated with patients with residual disease but not CPR. Based on the findings from our study, the current recommendation is still surgical resection regardless of the posttherapy PET SUV in the primary tumor. However, our study highlights the ability to detect patients with residual disease and the need to critically evaluate these patients for consideration of additional therapies.

Neuroendocrine markers expression in pancreatic serous cystadenoma.

BACKGROUND: The histologic diagnosis of pancreatic serous cystadenoma (SCA) is straightforward in most surgically resected specimens. However, in small biopsies, diagnosis could be challenging. Given the increased use of immunohistochemistry, we sought to investigate the expression of neuroendocrine markers in this entity and compare it with pancreatic neuroendocrine tumors (NETs). MATERIALS AND METHODS: Eighteen NET and 12 SCA cases were collected from our files. The cases were stained with CD56, synaptophysin, and chromogranin A. The percentage of positive cells was recorded. A percentage greater than 10 was considered as the cutoff. Fisher exact test was used for statistical analysis. RESULTS: For SCA, CD56, synaptophysin, and chromogranin A were expressed in 75%, 92%, and 0% of the cases, respectively, whereas in NET they were expressed in 89%, 100%, and 83%, respectively. Therefore, only chromogranin A could differentiate between these 2 entities based on immunohistochemistry (P=0.003). The entrapped Langerhans islets in the walls of microcysts could be a pitfall. CONCLUSIONS: Our data indicate that a significant proportion of SCA shows positive immunoreaction to CD56 and synaptophysin. Therefore, these markers should be interpreted with caution, particularly in a problematic small biopsy setting.

C-MYC alterations and association with patient outcome in early-stage HER2-positive breast cancer from the north central cancer treatment group N9831 adjuvant trastuzumab trial.

PURPOSE: Findings from the human epidermal growth factor receptor 2 (HER2) -positive National Surgical Adjuvant Breast and Bowel Project (NSABP) B31 trial suggested that MYC/HER2 coamplification (> 5.0 copies/nucleus) was associated with additional benefit from adjuvant trastuzumab in patients with early-stage breast cancer. To further explore this relationship, we investigated associations between MYC amplification and disease-free survival (DFS) in a similar adjuvant trastuzumab HER2-positive breast cancer trial-North Central Cancer Treatment Group (NCCTG) N9831. PATIENTS AND METHODS: This analysis included 799 patients randomly assigned to receive chemotherapy alone or with concurrent trastuzumab on N9831. Fluorescence in situ hybridization (FISH) was performed by using a dual-probe mixture for MYC and centromere 8 (MYC:CEP8) on tissue microarrays. MYC amplification was prespecified as MYC:CEP8 ratio > 2.2 or average MYC copies/nucleus > 5.0. Exploratory variables included polysomy 8. RESULTS: In comparing DFS (median follow-up, 4.0 years) between treatments, patients with MYC:CEP8 ratio ≤ 2.2 (n = 618; 77%) and > 2.2 (n = 181; 23%) had hazard ratios (HRs) of 0.46 (P < .001) and 0.67 (P = .33), respectively (interaction P = .38). Patients with MYC copies/nucleus ≤ 5.0 (n = 534; 67%) and > 5.0 (n = 265; 33%) had HRs of 0.52 (P = .002) and 0.48 (P = .02), respectively (interaction P = .94). Patients with MYC:CEP8 ratio < 1.3 with normal chromosome 8 copy number (n = 141; 18%) and ≥ 1.3 or < 1.3 with polysomy 8 (n = 658; 82%) had HRs of 0.66 (P = .28) and 0.44 (P < .001), respectively (interaction P = .23). Patients with MYC copies/nucleus < 2.5 (n = 130; 16%) and ≥ 2.5 (n = 669; 84%) had HRs of 1.07 (P = .87) and 0.42 (P < .001), respectively (interaction P = .05). CONCLUSION: We did not confirm the B31 association between MYC amplification and additional trastuzumab benefit. Exploratory analyses revealed potential associations between alternative MYC/chromosome 8 copy number alterations and differential benefit of adjuvant trastuzumab.

Oncocytoma can be differentiated from its renal cell carcinoma mimics by a panel of markers: an automated tissue microarray study.

BACKGROUND: Differentiating oncocytoma from its renal cell carcinoma (RCC) mimics, particularly chromophobe RCC, can be difficult, especially when limited tissue is available for evaluation. This study presents a panel of markers that are readily available, easy to use, and useful for differential diagnoses of renal tumors. DESIGN: A renal cell neoplasm tissue microarray was constructed including oncocytoma (n=30), chromophobe RCC (n=18), conventional RCC (n=64), papillary RCC (n=50), and benign renal tissues (n=31). CK7, CD10, epithelial membrane antigen, renal cell carcinoma marker (RCCma), vimentin, and endogenous avidin-binding activity (EABA) were studied. An Automated Cellular Imaging System, was used to quantify the staining intensity. RESULT: EABA was positive in 97% of oncocytoma, 26% of conventional RCC and 35% of papillary RCC with granular/eosinophilic (G/E) features and 6% of chromophobe RCC. EABA was negative in RCC without G/E features. Vimentin and RCCma were positive in most RCC with G/E features (conventional, 78% and 71%; and papillary, 85% and 76%, respectively), and negative in oncocytoma. Vimentin was also negative in chromophobe RCC. CK7 was positive in up to 81% of papillary RCC and 63% of chromophobe RCC, and essentially negative in conventional RCC and oncocytoma. CONCLUSIONS: EABA is an excellent marker for oncocytoma, which can be useful in differentiating oncocytoma from chromophobe RCC. A panel of EABA, vimentin, and RCCma markers can be useful in discerning oncocytoma from RCC with G/E features. Vimentin can be useful in discriminating chromophobe RCC from papillary or conventional RCCs.

FISH diagnosis of acute graft-versus-host disease following living-related liver transplant.

Acute graft-versus-host disease (GVHD) is an uncommon but often fatal complication following liver transplant. We describe a GVHD case in which a female patient with primary biliary cirrhosis underwent a living-related liver transplant from her son. The human leukocyte antigen typing of the donor was homozygous at all loci. The recipient's human leukocyte antigen type was haplo-identical to that of the donor. A bone marrow aspirate performed for pancytopenia revealed a severely hypoplastic marrow. Fluorescent in situ hybridization (FISH) using X- and Y-chromosome probes demonstrated that 80% of marrow cells were of donor origin. Comparison of Giemsa-stained cell morphology and FISH showed that the erythroid precursor cells were predominantly of male pattern (XY). This report is one of only a few studies that prove the migration of a donor's hematopoietic stem cells to a recipient's bone marrow. We demonstrated that FISH analysis using sex chromosome probes is useful to confirm a diagnosis of GVHD following organ transplantation from a donor of the opposite sex. We also showed that donor hematopoietic stem cells in a liver graft can migrate to the recipient's bone marrow. We suggest that FISH is a rapid and reliable test for confirming the diagnosis of GVHD in a peripheral blood or skin biopsy sample.

High endogenous avidin binding activity: an inexpensive and readily available marker for the differential diagnosis of kidney neoplasms.

It has been documented that some tissues, such as salivary gland, liver, cardiac and skeletal muscles and kidney, have high level endogenous biotin or endogenous avidin binding activity (EABA). Limited data is available on EABA in renal cell neoplasms. A tissue microarray (TMA) was constructed that included oncocytoma (n=30), chromophobe renal cell carcinoma (RCC) (n=18), clear cell RCC (n=45), clear cell RCC with granular/eosinophilic (G/E) features (n=19), papillary RCC (n=21), papillary RCC with G/E features (n=29) and benign renal tissues (n=31). The TMA slides were stained with or without biotin blocker and analyzed using the automated cellular imaging system (ACIS(R)). Without biotin blocker, a high positive rate of EABA was found in oncocytoma (56/60, 93%) and normal renal tubules (46/60, 77%). A moderate positive rate of EABA was found in clear cell and papillary RCCs with G/E features (13/39, 33% and 19/55, 35%, respectively). Chromophobe RCC and RCC without G/E features had essentially no EABA. With biotin blocker, benign renal tissue and clear cell RCC were negative for EABA; but a significant number of renal oncocytoma (29/60, 48%) and a few papillary RCC with G/E features (5/52, 10%) remained positive for EABA. In conclusion, high EABA may be used to differentiate oncocytoma from chromophobe RCC, and the staining results must be interpreted with caution when avidin-biotin detection system is used in diagnosing renal neoplasms.