Reappraisal of HER2 status in the spectrum of advanced urothelial carcinoma: a need of guidelines for treatment eligibility.

Although human epidermal growth factor receptor 2 (HER2) may represent a therapeutic target, its evaluation in urothelial carcinoma of the bladder does not rely on a standardized scoring system by immunohistochemistry or fluorescent in situ hybridization (FISH), as reflected by various methodology in the literature and clinical trials. Our aim was to improve and standardize HER2 amplification detection in bladder cancer. We assessed immunohistochemical criteria derived from 2013 American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAPs) guidelines for breast cancer and investigated intratumoral heterogeneity in a retrospective multicentric cohort of 188 patients with locally advanced urothelial carcinoma of the bladder. Immunohistochemistry was performed on 178 primary tumors and 126 lymph node metastases, eligible cases (moderate/strong, complete/incomplete membrane staining) were assessed by FISH. HER2 overexpression was more frequent with 2013 ASCO/CAP than 2007 ASCO/CAP guidelines (p < 0.0001). The rate of positive HER2 FISH was similar between primary tumor and lymph node metastases (8%). Among positive FISH cases, 48% were associated with moderate/strong incomplete membrane staining that were not scored eligible for FISH by 2007 ASCO/CAP criteria. Among 3+ immunohistochemistry score cases, 67% were associated with HER2-positive FISH. Concordance between primary tumors and matched lymph node metastases was moderate for immunohistochemistry (κ = 0.54 (CI 95%, 0.41-0.67)) and FISH (κ = 0.50 (CI 95%, 0.20-0.79)). HER2-positive FISH was more frequent in micropapillary carcinomas (12%) and carcinoma with squamous differentiation (11%) than in pure conventional carcinoma (6%). Intratumoral heterogeneity for HER2 immunohistochemistry was observed in 7% primary tumor and 6% lymph node metastases; 24% positive HER2 FISH presented intratumoral heterogeneity. Our study suggests that HER2 evaluation should include an immunohistochemistry screening step with eligibility for FISH including incomplete/complete and moderate/strong membrane staining. Spatial or temporal intratumoral heterogeneity prompts to perform evaluation on both tumor and lymph node, and for each histological variant observed.

Double-staining chromogenic in situ hybridization as a useful alternative to split-signal fluorescence in situ hybridization in lymphoma diagnostics.

BACKGROUND: Malignant lymphomas are classified based on morphology, immunophenotype, genetics and clinical features. The pathological diagnosis is generally considered difficult and prone to mistakes. Since non-random chromosomal translocations are specifically involved in specific entities, their detection is an important adjunct for increasing the reliability of the diagnosis. Recently, split-signal fluorescence in situ hybridization has become available as a robust method to detect chromosomal breaks in paraffin-embedded formalin-fixed tissues. A bright field approach would bring this technology within the reach of every pathology laboratory. DESIGN AND METHODS: Our study was initiated to determine the consistency between chromogenic in situ hybridization and fluorescence in situ hybridization, both using split-signal probes developed for the detection of chromosomal breaks. Five hundred and forty cases of 11 lymphoma entities and reactive, benign lymphoid tissues, collected from eight different pathology laboratories, placed on 15 fluorescence in situ hybridization pre-stained tissue microarray slides, were double stained for the chromogenic hybridization. For each core morphology and actual signal were compared to the original fluorescence hybridization results. In addition, hematoxylin background staining intensity and signal intensity of the double-staining chromogenic in situ hybridization procedure were analyzed. RESULTS: With respect to the presence or absence of chromosomal breaks, 97% concordance was found between the results of the two techniques. Hematoxylin background staining intensity and signal intensity were found to correspond. The overall morphology after double-staining chromogenic in situ hybridization had decreased compared to the initial morphology scored after split-signal fluorescence in situ hybridization staining. CONCLUSIONS: We conclude that double-staining chromogenic in situ hybridization is equally reliable as fluorescence in situ hybridization in detecting chromosomal breaks in lymphoid tissue. Although differences in morphology, hematoxylin staining and chromogenic signal intensity vary between the tumor entities none of the entities appeared more easy or difficult to score.