Accuracy of diagnosing mantle cell lymphoma and identifying its variants on fine-needle aspiration biopsy

Background: Mantle cell lymphoma (MCL) is an incurable B-cell lymphoma portending an aggressive clinical course; the blastoid and pleomorphic morphological variants have an even worse prognosis. In addition, patients with classic morphology and a high proliferation index (HPI), also have reduced survival. Although variants have been defined, to the authors’ knowledge the ability to detect these subtypes by fine-needle aspiration biopsy (FNAB) has not been described. Methods: MCL cases diagnosed by lymph node FNAB with concurrent core needle biopsy were reviewed from 146 patients, accounting for 172 specimen pairs. FNAB and core needle biopsy diagnoses were compared to determine concordance rates. Flow cytometric immunophenotype and Ki-67 rates were evaluated. Results: The classic subtype was diagnosed in 58% of cases (99 of 172 pairs) and variant morphology was diagnosed in 42% of cases (73 of 172 pairs) by histology. Twenty-nine patients presented with variant morphology whereas 28 underwent transformation. A nontraditional immunophenotype including loss of CD5 or FMC-7 and expression of CD23 and CD10 was found in 44% of variants (29 of 66 variants) and 19% of classic subtypes (18 of 94 classic subtypes) (P =.0008). Ki-67 rates averaged from 56% to 76% for blastoid and pleomorphic cases, 53% to 55% for MCL-HPI cases, and 17% to 19% for classic cases. The sensitivity and specificity to detect MCL variants by FNAB were 74% and 93%, respectively. Conclusions: The accuracy of diagnosing MCL is high when adequate samples for cytomorphology and flow cytometry are obtained. Subtyping variants by cytomorphology alone has challenges, but overall demonstrates high sensitivity and specificity. The performance of Ki-67 on cytology specimens is useful for detecting MCL with HPI.