ABSTRACT
Introduction:
Fluorescence in situ hybridization (FISH) is an essential ancillary study used to identify clinically aggressive subsets of large
B-cell lymphomas that have MYC, BCL2, or BCL6 rearrangements. Small-volume
biopsies such as
fine needle aspiration biopsy (FNAB) and
core needle biopsy (CNB) are increasingly used to
diagnose lymphoma and obtain material for ancillary studies such as FISH. However, the performance of FISH in small
biopsies has not been thoroughly evaluated or compared to surgical
biopsies.
Methods:
We describe the results of MYC, BCL2, and BCL6 FISH in a series of 222
biopsy specimens, including FNAB with
cell blocks, CNBs, and surgical excisional or incisional
biopsies from 208 unique
patients aggregated from 6
academic medical centers. A subset of
patients had FNAB followed by a surgical
biopsy (either CNB or excisional
biopsy) obtained from the same or contiguous anatomic site as part of the same clinical workup; FISH results were compared for these paired specimens.
Results:
FISH had a low hybridization failure rate of around 1% across all specimen types. FISH identified concurrent MYC and BCL2 rearrangements in 20 of 197 (10%) specimens and concurrent MYC and BCL6 rearrangements in 3 of 182 (1.6%) specimens. The paired FNAB and surgical
biopsy specimens did not show any discrepancies for MYC or BCL2 FISH; of the 17
patients with 34 paired
cytology and surgical specimens, only 2 of the 49 FISH probes compared (4% of all comparisons) showed any discrepancy and both were at the BCL6 locus. One discrepancy was due to
necrosis of the CNB specimen causing a false negative BCL6 FISH result when compared to the FNAB
cell block that demonstrated a BCL6 rearrangement.
Discussion:
FISH showed a
similar hybridization failure rate in all
biopsy types. Ultimately, MYC, BCL2, or BCL6 FISH showed 96% concordance when compared across paired
cytology and surgical specimens, suggesting FNAB with
cell block is equivalent to other
biopsy alternatives for evaluation of DLBCL or HGBCL FISH testing.
