China Science

BACKGROUND: Mastocytosis is an abnormal proliferation of mast cells and theirsubsequent accumulation in various organs. Diagnosis of mast cell disease relies on properidentification of abnormal mast cells. CASE: A 55-year-old man presented with a history of fever forseveral months, associated with night sweats, involuntary 20lb weight loss, progressive fatigue,weakness, worsening abdominal distention, shortness of breath, and diffuse lymphadenopathy. Physicalexamination and computed tomography (CT) showed hepatosplenomegaly, massive ascites, andgeneralized lymphadenopathy. Bone marrow biopsy with immunohistochemistry (ICH) studies revealedmastocytosis. CT-guided fine needle aspiration biopsy (FNAB) of the retroperitoneal lymphadenopathywas performed. The smears were cellular for a mixed population of mature plasma cells, eosinophils,left-shifted granular and lymphoid cells, and abundant abnormal mast cells. The mast cells had roundto oval lobulated nuclei, some of which were binucleated or eccentrically located, with coarse,evenly distributed chromatin. Abundant pale cytoplasm contained numerous metachromatic granules. IHCstudies and flow cytometry confirmed the cytologic diagnosis of mastocytosis. CONCLUSION: This casehighlights the cytologic features of mastocytosis in FNA specimens. IHC stains and flow cytometryare helpful to confirm the cytologic diagnosis. To the best of our knowledge, this is the secondcase that describes the cytologic characteristics of mastocytosis.

Tongson-Ignacio,JE　Gu,M
Department of Pathology and Laboratory Medicine, University of CaliforniaIrvine Medical Center, 101 The City Drive, Orange, California 92868, USA.

Antibodies　 Azure Stains　 Biopsy, Fine-Needle　 Cytodiagnosis　 HumansImmunohistochemistry