Author of

• 16549

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  P1.02 - Poster Session with Presenters Present (ID 454)

  • Event: WCLC 2016
  • Type: Poster Presenters Present
  • Track: Biology/Pathology
  • Presentations: 1
  • Moderators:
  • Coordinates: 12/05/2016, 14:30 - 15:45, Hall B (Poster Area)

  • 16578

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    P1.02-029 - Infrequent Staining Patterns in ALK Immunohistochemistry: Correlation with Fish Analysis (ID 5208)

    14:30 - 15:45  |  Author(s): P.X. De La Iglesia
    • Abstract

    Background:
    AKL gene rearrangements are predictive alterations in non small cell lung carcinomas (NSCLC). Immunohistochemistry (IHC) has become a valuable tool in assessing ALK status, however unusual staining patterns, such as heterogeneous diffuse moderate and focal intense stains, may occur and can make evaluation difficult.
    
    Methods:
    We correlated immunohistochemistry unusual staining patterns with ALK status by fluorescence in situ hybridization (FISH). Of 851 cases tested, we found 14 (1.6%) cases with inconclusive staining patterns that can be summarized in: a) diffuse granular cytoplasmic moderate stain, with or without background mucin stain (10 cases) b) focal intense granular cytoplasmic stain in overall negative or weakly positive tumors (4 cases). IHC was performed on an automatized Benchmark staining module using Ventana ALK (D5F3) CDx assay with Optiview amplification kit. FISH was performed using ALK break-apart probe set (Vysis LSI ALK Dual Color, Abbott Molecular). Cases were considered ALK-FISH positive if ≥15% tumor cells showed split red and green signals (separation of 2 diameters or more) and/or single red signals
    
    Results:
    Of 10 moderate granular cytoplasmic stain cases, 4 had also abundant mucin backround stain 6 where markedly heterogeneous with areas of weak and moderate cytoplasmic granular stain. Nine were FISH negative, one yielded no signals (uninformative result) and one specimen corresponded to an acid decalcified specimen and was not evaluated by FISH. Focal intense stain was observed in 5 samples, 3 corresponded to surgical specimens and the rest to small needle biopsies, one of the surgical specimens was FISH positive and the rest, negative.
    
    Conclusion:
    Since FDA approval of Ventana ALK (D5F3) IHC CDx Assay, IHC has become a widely used tool for assessing ALK status. Guidelines suggest that weak granular stain should be interpreted as negative and focal intense granular stain in any number of cells, as positive. Even though our sample is small, moderate granular stain was consistently negative by FISH analysis, however, focal intense stain shows more discordant results between tests. To date, no suggestions are made on what should be the minimum amount of tumor in a sample to report an IHC assay. Even though some of these patients with IHC positive/FISH negative results have been reported as responders to Crizotinib, further studies are needed. One specimen with moderate cytoplasmic IHC stain was uninformative due to lack of signals. This raises the issue of the need to standardize preanalytical variables, which can be difficult in some areas of Latin America.