Hematopathology / BONE MARROW BIOPSIES

The medical records of 21 patients evaluated for mastocytosis and 2 patients seen for follow-up of known mastocytosis who underwent bilateral iliac crest aspirations and biopsies were reviewed retrospectively to determine whether mastocytosis could be confirmed in each of a patient’s biopsy specimens. In 19 cases (83%), each biopsy specimen showed evidence of mastocytosis; however, in 4 cases (17%), only 1 of 2 biopsy sites revealed mastocytosis. Compared with the 4 patients with only a unilateral positive biopsy result, the bilateral group had significantly higher urinary excretion of 11β-prostaglandin F2α , higher serum tryptase levels, and higher serum calcitonin values, and a higher percentage had splenomegaly (37% [7/19] vs 0% [0/4]). The 2 groups could not be distinguished by the main initial symptom(s), presence of urticaria pigmentosa, or other laboratory findings (alkaline phosphatase, aspartate transaminase, or hemoglobin concentrations or total WBC, total eosinophil, or platelet counts). Bilateral biopsies might be useful for diagnosing early systemic mastocytosis or detecting minimal bone marrow involvement. The diagnosis of systemic mastocytosis depends partly on finding mast cell infiltration of extracutaneous tissue. The bone marrow commonly is chosen as the site for biopsy. In addition to systemic mastocytosis, an increase in bone marrow mast cells may accompany such hematologic disorders as chronic lymphocytic leukemia, non-Hodgkin lymphoma,1 dysmyelopoiesis, and myeloproliferative disorders.2 Hence, in the evaluation of a patient for systemic mastocytosis, bone marrow aspiration and biopsy serve 2 purposes: to confirm the diagnosis of mastocytosis and to evaluate the bone marrow for associated hematologic disorders. The number of mast cells detected in bone marrow samples has been shown to correlate positively with the urinary excretion of tele-methylimidazoleacetic acid, the primary histamine metabolite.3 Although skeletal scintigraphic findings in mastocytosis might show multifocal or diffuse abnormalities, the radionuclide bone patterns might be normal or show only unifocal involvement.4 Also, only patchy or focal infiltration patterns involving peritrabecular or perivascular regions or areas around lymphoid aggregates might be evident, rather than diffuse infiltration.5 To determine whether the presence of mastocytosis could be missed because of sampling error, we retrospectively reviewed the findings in each of the bilateral biopsy sites of 21 patients who had been evaluated for systemic mastocytosis during the previous 5 years and 2 patients with known disease with bilateral biopsies at the time of follow-up. Materials and Methods The medical records of patients with the diagnosis of systemic mastocytosis who had bilateral biopsies performed Hematopathology / ORIGINAL ARTICLE Am J Clin Pathol 2004;121:264-267 265 265 DOI: 10.1309/2EWQKN00PG02JKY0 265 © American Society for Clinical Pathology during their evaluation or follow-up during the past 5 years were selected for retrospective review. Patients who had undergone only a unilateral biopsy (with positive or negative results for systemic mastocytosis) were not included. Slides from each bone marrow biopsy specimen were examined for the presence of mastocytosis by a hematopathologist (C.-Y.L.) and classified according to the World Health Organization (WHO) criteria.6 Bone marrow biopsy specimens were stained routinely for the presence of mast cells with an immunohistochemical stain for tryptase.7 The presence or absence of mast cell infiltrates was assessed in the leftand right-sided specimens, and the percentage of involvement was estimated by direct visualization. The following laboratory results were compared between the group with bilaterally positive results of bone marrow biopsies and the group with a positive bone marrow biopsy result in only 1 of 2 sites: alkaline phosphatase, aspartate transaminase, and hemoglobin concentrations; total leukocyte, total eosinophil, and platelet counts; serum tryptase and serum calcitonin concentrations; and 24-hour urinary excretion of 11β-prostaglandin F2α. Any available bone scan and bone radiographic reports also were reviewed and compared. Statistical Analysis The Mann-Whitney test was used to determine the statistical significance of comparisons between laboratory results for patients with bilateral bone marrow involvement and for patients with unilateral involvement. The InStat 2.03 computer program (GraphPad Software, San Diego, CA) was used.