The additional role of bone marrow particle sections (‘clot sections’) in confirming marrow involvement by multiple myeloma: a single centre study

Sir, Recent recommendations on the diagnosis of multiple myeloma (MM) are based on the presence of features of myeloma-related organ or tissue impairment and demonstration of clonal plasma cells in bone marrow aspirates. Trephine biopsy has also been advised at diagnosis to allow evaluation of post treatment response when marrow aspiration yields a poor quality sample (BCSH Guidelines 2005 in Smith et al., 2006). However, the value of routine trephine biopsy has been questioned by others (Charles et al., 2004). We, therefore, retrospectively studied marrow smears, bone marrow particle sections (‘clot sections’), and trephine biopsies from 96 patients with MM diagnosed and followed up at a single tertiary care centre during a 10-year period. At our centre, in addition to marrow smears and trephines, we routinely collect approximately 0.5–1.0 ml of aspirated marrow in 50 ml of 10% formalin fixative which is processed to make ‘clot sections’ as follows. After overnight fixation, supernatant is poured off and 70% alcohol added to induce red cell lysis. Marrow particles are then picked-up with the help of a Pasteur pipette, placed on ‘speci-wrap’, covered in 0.2% basic fuchsin to highlight the tissue and processed through alcohol, xylene and embedded in paraffin wax as per standard histological processing. Samples are not decalcified. 3–5 lm H&E stained ‘clot sections’ are available for study within 48–72 h of collection. Smears were regarded inadequate if aparticulate or clotted. Particulate smears showing less than 10% of plasma cells were considered negative. For marrow trephines, a 10 · 2-mm thick biopsy was considered adequate. The clot sections were inadequate if no granules were seen. A total of 219 smears, 196 clot sections and 184 trephines were studied for their concordance, and, in particular, the usefulness of bone marrow clot sections in the confirmation of marrow involvement by MM. Overall, 158 smears, 148 clot sections and 142 trephines were available for repeat histopathological review by the authors themselves. When study material was not available or was inadequate for histopathological review because of faded staining, results were recorded from historical computerized data. At diagnosis, 94 smears, 81 clot sections and 79 trephine biopsies were studied respectively. The remainder were at disease follow-up or at relapse. Samples from 31 patients (32.3%) were nonconcordant (Table 1). Marrow smears were noncontributory in 29.1% (n = 28) of patients. They were inadequate for three patients and negative for four patients at diagnosis. At follow-up, they were inadequate for seven patients and negative for another 14 patients (grouped together as negative smears in Table 1). Trephines provided the diagnosis in 82% of these patients (23/28); and in nine of these 23 (39%), the clot sections were also negative. The clot section provided the diagnosis in 75% of these patients (19/28); and in five of these 19 (26%), the trephine biopsy was negative. Overall marrow trephines were negative in 8.3% of cases (n = 8). Clot sections yielded a similar false negative rate of 9.3% to trephine biopsy (n = 9). Examination of both smears and trephines has previously been also recommended based on such discrepant results (Buss et al., 1987; Terpstra et al., 1992 & Rajkumar et al., 2001). However, the limitations of trephine biopsy in MM have been noted in this Journal (Charles et al., 2004). Evaluation of clot sections is straightforward, speedy as no decalcification is required and avoids the time, discomfort and potential for complications associated with trephine biopsy. Immunohistochemical studies on trephine biopsy have recently been reported to be more sensitive in detecting the plasma cell infiltration (Joshi et al., 2008) than marrow aspiration. Tissue histochemistry is easily performed on clot sections and in some circumstances, may give better results than on trephine biopsy (Dunphy, Nies & Gabriel, 2007). Our results show that additional analysis of marrow clot sections is valuable in establishing the diagnosis of MM by reducing the false-negative rate in diagnosis, particularly in follow-up specimens. Our current practice is now to undertake marrow aspiration for smears and clot sections in conjunction with CD 138 staining on the clot sections in all patients with a known or suspected diagnosis LETTER TO THE EDITOR INTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY