Correlation between molecular and histopathological diagnoses of B cell lymphomas in bone marrow biopsy and aspirates

PCR has been shown previously to be the most sensitive technique to detect a clonal population in marrow aspirates (MAs), and the clinical standard for evaluation of bone marrow lymphoma involvement today is bone marrow trephine biopsy (BMTB). The goal of this study was to compare morphological evaluation of B cell neoplasm in BMTB (histology and immunohistochemistry) and PCR analysis in MA, with both specimens obtained at the same time, in patients with a known molecular marker of the disease.

This was a retrospective evaluation of 98 consecutive BMTB specimens from 60 patients with a known B-cell neoplasm and a previous PCR marker of the disease (BCL2 and/or IGH).

Considering the IGH PCR cases alone, a B cell clone was detected in 85% and 39% of the morphology (M) positive and negative groups, respectively. Five M(+), IGH(-) cases were found, including two cases of follicular lymphoma (FL), one case of diffuse large B cell lymphoma, and two cases of mantle cell lymphoma. The FLs had about 20% and 50% of BMTB involvement each. All other cases had minimal lymphoma localisation. The two FLs were also BCL2-MBR(+). Use of BCL2-MBR detected all M(+) cases and 66% of M(-) cases whenever it was an initial marker of disease.

IGH PCR alone is not good enough for BMTB assessment, especially in FL. On the other hand, the PCR study for BCL2 is more sensitive than morphology, without any false negative results in this series, suggesting that BCL2-MBR PCR on MA can be used as an alternative and more sensitive examination for disease evaluation, providing that there is careful analysis of data, adequate knowledge of PCR pitfalls and absence of other haematological disorders.