[1401] Mastocytosis and Associated Clonal Hematological Non-Mast Cell Lineage Neoplasm: A Diagnostic Challenge

M Naghashpour, L Zhang, H Cualing, L Moscinski. Moffitt Cancer Center/Univ. of South Florida, Tampa, FL

Background: Mastocytosis has many features in common with other myeloproliferative neoplasms (MPN) and is recognized by WHO as a major subgroup of MPNs. In 20-30% of patients with systemic mastocytosis (SM), an associated clonal hematological non mast cell lineage disease (AHNMD) is also diagnosed, and such an occurrence is recognized by WHO as SM-AHNMD. The latter (AHNMD) includes predominantly myeloid, but also non-myeloid hematologic neoplasms. SM-AHMD often creates a clinicopathologic diagnostic challenge due to diverse clinical presentation and sometimes subtle morphologic findings. We reviewed the clinicopathologic features, cytogenetic and molecular findings of 8 patients with SM-AHNMD.
Design: Approximately 32,000 bone marrow (BM) biopsy reports at Moffitt Cencer Center from 01/1996 to 07/2009 were reviewed. Thirty patients with SM were identified. Diagnosis was confirmed by BM biopsy histomorphology and ancillary tests; SM- and AHNMD-components were classified according to WHO criteria. Clinical presentation, laboratory data, phenotypic and molecular studies, and clinical course were reviewed.
Results: SM was diagnosed in 30 BM biopsies (0.1 %). SM-AHNMD was diagnosed in 8 patients (27% of SM) over a 13-year period. The AHNMD were MDS (3), MDS/MPN (2), AML (1), marginal zone lymphoma (1) and IgD plasma cell myeloma (1). Patients ranged in age from 54 to 78 years (average 57), with M:F of 1:1. At presentation, all patients (8/8) had cytopenia; two (2/8) additionally had monocytosis. Cytogenetic abnormalities were identified in 3 cases (3/4) [t(8;21), t(3;5), isochromsome 14, del (5q), trisomy 4]. The c-Kit D816V point mutation was detected in 3 cases (3/4). In six patients (6/8), SM was diagnosed concurrently with the AHNMD and mast cell proliferation was detected only after complete histopathologic examination. These six had no characteristic synptoms related to SM. Two patients (2/8) had previous long-standing indolent SM with cutaneous manifestations.
Conclusions: SM-AHNMD is uncommon. AHNMD is usually myeloid, but can also be a lymphoid/plasma cell neoplasm. In the majority of our cases, mastocytosis was not clinically suspected and the patient's clinical presentation was related to the associated non-mast cell lineage neoplasm. SM component may be subtle histomorphologically. SM-AHNMD might pose a histopathologic challenge that potentially could be missed. It is essentially a histomorphological diagnosis that may require additional phenotypic and molecular-genetic studies.
Category: Hematopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 192, Wednesday Afternoon


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