Fluorescent in Situ Hybridization Analysis at Bone Marrow Biopsy Section in Multiple Myeloma.

The technique of fluorescence immunophenotyping and interphase cytogenetics as a tool for the investigation of neoplasms has recently been introduced to detect molecular cytogenetic abnormalities in plasma cell myeloma of bone marrow (BM) aspirate. However, in case of sub-optimal BM aspirate or the focal distribution of myeloma in the BM, the plasma cells are significantly lower in the BM aspirate than those of biopsy section. Therefore, we have developed a sensitive fluorescence in situ hybridization (FISH) technique which is combined with immunochemistry and is applicable to BM biopsy section for molecular cytogenetic study of plasma cell neoplasms.

Conventional cytogenetic analysis and FISH results of BM samples of 35 multiple myeloma (MM) patients at the time of diagnosis have been evaluated. The probe for IgH rearrangement has been used for hybridization with myeloma cells coupled with CD138 immunostain at BM biopsy section.

Nineteen patients (54.3%) had abnormal FISH IgH results in biopsy section, whereas seven (20%) cases had abnormal findings in BM aspirate. FISH IgH analysis at biopsy section revealed various signal patterns and proportions (range 6-87%) of cells with atypical signals out of CD138 positive cells. Among five cases with <10% of plasma cells at BM aspirate, four (80%) had abnormal FISH results at biopsy section, whereas one (20%) had abnormal signals at aspirate. There is no correlation between the proportions of cells with atypical signal corrected by the plasma cell count at BM aspirate and the proportions of cells with atypical signal at biopsy section.

FISH analysis combined with immunostain which is applied at biopsy section is a highly sensitive and convenient technique to detect and quantify monoclonal plasma cells. It could be used for molecular cytogenetic study in plasma cell neoplasms even though there are less than 10% of plasma cells at BM aspirate and the monitoring of residual disease.

Kong:National cancer center, Korea: Research Funding.