MYB Translocation t(6;9) in Adenoid Cystic Carcinoma Fine Needle Aspiration Biopsy Using Fluorescence In-Situ Hybridization
Jena B Hudson, Diane H Robirds, Brian T Collins. Washington University in St Louis, Saint Louis, MO
Background: Salivary gland neoplasms evaluated by fine needle aspiration (FNA) biopsy can have a wide variety of appearances with considerable morphologic overlap between various benign and malignant entities. A general morphologic categorization of “basaloid” neoplasm is a frequently encountered pattern and diagnostic challenge. The main differential diagnostic considerations include benign mixed tumors/monomorphic adenoma (BMT) and adenoid cystic carcinoma (ACC). There is consensus agreement that FNA biopsy cytomorphology alone does not permit distinction. The value of distinguishing the two entities is related to their biologic behavior and initial surgical approach. Chromosomal abnormalities of ACCs have not been commonly evaluated in FNA biopsy material. MYB gene translocation t(6;9) (q22-23;p23-24) has been identified in around 50% of formalin fixed paraffin embedded (FFPE) tissue and has been absent in other salivary gland neoplasms, including benign mixed tumors.
Design: Patients who underwent FNA biopsy for known and surgically confirmed ACC and BMT were identified and smears from air-dried modified Wright-Giemsa stained slides selected. The direct smear slide was used for fluorescence in-situ hybridization (FISH) utilizing a protocol optimized for direct FNA smears. Commercially available red and green fluorescent labeled probes, hybridizing to MYB-telomeric and MYB-centromeric, were used to identify the MYB gene and evaluate for a translocation. Using a fluorescent microscope, at least fifty DAPI stained non-overlapping cells of interest were counted per case.
Results: 6 ACCs and 5 BMT FNA cases underwent FISH evaluation for MYB translocation. Utilizing a fluorescent microscope and DAPI stained nuclei; at least fifty cells of interest were evaluated for the presence of the MYB gene and evidence of a break-apart signal. One half of the ACCs (3/6) showed a positive break-apart signal in the majority of the 50 cells counted. Of the 5 BMTs, none of the 50 cells counted showed a MYB translocation.
Conclusions: The MYB gene was present by FISH evaluation in the BMT and ACC FNA smears. The BMT cases demonstrated the MYB gene without evidence of translocation. For the ACC cases, the MYB translocation was present in half the cases (50%). This corresponds to the reported prevalence in FFPE tissue for ACC surgical resections. Utilizing FISH testing of salivary gland FNA cases for MYB translocation t(6:9) in select cases has the potential to provide additional specific diagnostic information.
Tuesday, March 5, 2013 1:00 PM
Poster Session IV # 72, Tuesday Afternoon