Fluorescence In Situ Hybridization (FISH) for the Detection of the (8;14) Translocation in Archival Fine Needle Aspirates of Suspected Burkitt Lymphomas (BL).

The detection of the chromosomal translocations involving the myc gene, characteristic of BL, is important in the diagnostic workup of agressive lymphomas given its impact on treatment strategies and prognosis. Recently this has been accomplished using FISH techniques either in paraffin-embedded tissue sections or fresh tumor aspirates. BL has an elevated cellular turn-over and a rapid diagnosis is highly desirable; this, and its high incidence in pediatric populations in whom organ biopsy needs general anesthesia, makes fine needle aspiration (FNA) samples attractive for diagnosis. In some cases, confirmation of the diagnosis may require the analysis of archival pre-stained samples. However, only recent samples have been reported as suitable for FISH analysis. We analysed 18 cytological samples (8 cytospins and 10 smears) obtained by FNA from 16 male and two female patients, median age 7.5 (3 to 48) years old, diagnosed with BL (15), atypical BL (1) or high grade lymphoma with a difficult differential diagnosis with BL (3) between February 2000 and July 2004 on the basis of morphology and phenotype of cytological and/or histological samples. In all cases the presentation and further clinical course suggested the possibility of BL and treatment was administered accordingly. Sixteen smears were May-Grunwald-Giemsa (MGG) stained whereas two were fresh-frozen; the samples had been stored for variable periods (1 day to 53 months). Cytology specimens (6 MGG-stained and 6 frozen) obtained from 12 reactive lymph nodes were used as controls, to determine the cut-off value for positive hybridization signals. After removal of the coverslips with xylene, the slides were destained in a series of water and ethanol washes. Pretreatment with pepsin was followed by the hybridization procedure. The dual fusion t(8;14) fluorescent probe was purchased from Vysis. Eleven out of 18 (61%) samples could be hybridized using this technique. The 7 cases without an interpretable signal were between 9 and 53 months old. The cut-off value for t(8;14) was 0%, meaning that in 12 negative controls the pattern of two fusion signals with or without a remaining signal from der(8) chromosome was never observed. In aggreament to previous publications 8 out of 11 specimens (72%) were positive for the (8;14) translocation, including 3 cases in which a definitive BL diagnosis could not be made by cytology/histology alone. The median percentage of positive cells was 80% (46 and 92%). Although the quality and age of the smears influenced the results, and better signals were observed with frozen specimens, FISH analysis of archival cytopathological material stored for prolonged periods was frequently possible and allowed the diagnosis of 3 difficult cases, whereas it confirmed the morphological results in another 5 patients.