ABSTRACT
Sclerotic tissue may be difficult to process for FC and yield enough cells for analysis. In the bone marrow, lack of clonal B-cell population by FC analysis does not necessary exclude involvement by lymphoma. Due to paratrabecular location of neoplastic lymphoid aggregates and/or due to reticulin fibrosis which often accompanies lymphoid infiltrate in the bone marrow, flow cytometry often does not reveal clonal B-cell population. The discrepancy between the number of clonal plasma cells detected by FC and actual extent of bone marrow involvement is due to drop-out of neoplastic cells during bone marrow aspiration and sample preparation. Plasma cells have delicate cytoplasm which often get destroyed during tissue processing leading to the under-representation of neoplastic cells on FC displays. Since the FC analysis relies mostly on detection of membrane/cytoplasmic antigens, neoplastic cells with delicate and fragile cytoplasm are often underestimated or even absent, despite replacement of the bone marrow by neoplastic cells.
