Fluorescence in situ hybridization: method of choice for a definitive diagnosis of mantle cell lymphoma.

Fluorescence in situ hybridization (FISH) using IGH/CCND1 probes was used to analyze 35 specimens including 27 paraffin sections, 3 bone marrow aspirates, and 5 peripheral blood smears. The 27 paraffin sections included 7 bone marrows, 10 lymph nodes, 3 spleens, 3 tonsils, 3 gastrointestinal biopsies, and 1 skin biopsy. Among these cases, 23 specimens were from 20 patients with mantle cell lymphoma (MCL) and 12 specimens were from 12 patients with non-MCL lymphomas/lymphoid hyperplasia. Specimens from all MCL patients showed positive results with FISH. In one patient, the archived paraffin sections were negative with FISH, but a fresh peripheral blood specimen showed a positive result. Negative results were obtained in all specimens from non-MCL cases. Flow cytometric analysis revealed that all cases of MCL showed CD19/CD5 staining, but the percentages of cells positive for CD23 and FMC-7 were variable, thus they cannot be depended upon for a definitive diagnosis of MCL. Immunohistochemical stains demonstrated positive staining for CD5 and CD20 and negative staining for CD23 in MCL cases but cyclin D1 was positive in only 10 of 13 MCL cases studied. Therefore, it appears that immunophenotyping alone is not sufficient to establish a definitive diagnosis of MCL. FISH should be routinely used when the diagnosis needs confirmation. FISH can be performed in a routine clinical laboratory, and it is applicable to archived material for retrospective studies. Other molecular cytogenetic techniques in comparison with FISH are discussed.