Fluorescence in situ hybridization studies on direct smears

BACKGROUND: In the fine-needle aspiration biopsy (FNAB) diagnosis of B-cell non-Hodgkin lymphomas (B-NHL), the role of flow cytometry (FC) can be limited because of nondiagnostic findings. Fluorescence in situ hybridization (FISH) studies, similar to FC, can be helpful in establishing clonality and in subclassifying the lymphoma. The aim of the current study was to determine whether FISH studies performed on unstained direct smears improved the ability to diagnose and/or subclassify B-NHL on FNAB. METHODS: A total of 181 cases of B-NHL diagnosed by FNAB were retrieved. The cytomorphology, ancillary study results, clinical information, and available pathologic follow-up were reviewed. RESULTS: Of the 181 cases, FISH studies were performed in 106 cases (59%). The indications for FISH studies were for subclassification (59 cases; 56%) and nondiagnostic or unavailable FC results (47 cases; 44%). Of the 59 cases submitted for subclassification, 23 cases (39%) were successfully subclassified. The 47 cases with nondiagnostic or unavailable FC results included cases in which FC demonstrated a surface immunoglobulin-negative population (19 cases; 40%), had insufficient cellularity (18 cases; 38%), yielded negative results (6 cases; 13%), or had no specimen submitted (4 cases; 9%). In this group, 26 cases (55%) demonstrated an immunoglobulin heavy-chain gene rearrangement and/or chromosomal translocation. CONCLUSIONS: The results of the current study illustrate that FISH studies performed on unstained direct smears play a complementary role to FC in establishing the diagnosis and/or subclassification of B-NHL. Thus, the preparation of unstained smears at the time of FNAB can be helpful for potential FISH studies.