[Options for histological examination of bone marrow during diagnosis of multiple myeloma]

The quantification of plasma cells in bone marrow is an essential step in plasma cell dyscrasia diagnostics. Besides cytological examination of bone marrow aspirates, plasma cells can also be quantified by histological examination of samples obtained by sternal puncture or trephine biopsy. Acquired bone marrow particles dispersed in aspirated marrow blood are usually sufficient for microscopic diagnosis. Histological examination offers, in comparison with cytology alone, several advantages. In this method, the number of plasmacytes is not distorted by their dilution by peripheral blood cells. Acquired material can be stored for a long time without showing any changes and it allows multiple re-use for purposes of prospective determination of other parameters. Plasmacyte count in histological sections is difficult and laborious and is not a routine practice. A qualified estimate ofplasmacyte percentage allows classification into the none/small/big criterion categories according to the WHO diagnostic scheme. Cell count using digital imaging is also possible, even using software image analysis, but this method requires a digital camera coupled with a microscope. Besides elementary plasmacyte count, it is also possible to determine their mono- or polyclonality. This reaction has certain technical pitfalls and its evaluation is sometimes impossible. Determination of some antigens' expression has prognostic (Ki67 index), predictive (CD56) or therapeutic (CD20, CD40, CD74, etc) significance. Histological material can also be used for interphase fluorescent in situ hybridisation.