P223 | MASTOCYTOSIS ASSOCIATED WITH LYMPHOPROLIFERATIVE DISORDERS: A SINGLE-CENTER CASE SERIES

Mastocytosis is a rare neoplastic disease originating from mast cells, which in approximately 20% of cases occurs concurrently with another hematologic malignancy, as recognized by the WHO 2022 classification. In about 90% of these cases, the associated condition is a myeloid neoplasm. Reports of mastocytosis associated with lymphomas are rare in the literature, and data on biological mechanisms, clinical behavior, treatment, and prognosis are limited. We retrospectively identified 5 patients diagnosed with both mastocytosis and a lymphoproliferative disorder. Three out of five were male, with a median age of 58 years at the diagnosis of mastocytosis. The lymphoproliferative disorders observed were: chronic lymphocytic leukemia, marginal zone lymphoma, mantle cell lymphoma, diffuse large B-cell lymphoma (DLBCL), and lymphoplasmacytic lymphoma. In 4 patients (80%), both diagnoses were made concurrently, while in one case (20%) the lymphoproliferative disorder (DLBCL in complete remission after chemotherapy) preceded the diagnosis of mastocytosis. In 60% of cases, both diseases were identified in bone marrow biopsy, while in 40% the lymphoproliferative disorder was found only in an extramedullary site. In all cases, mastocytosis was indolent, without B or C findings. The median follow-up from the diagnosis of mastocytosis was 44 months. None of the patients required treatment for mastocytosis, nor showed signs of disease progression. A history of allergic reactions was reported in only one patient (20%). All patients showed elevated serum tryptase levels (mean 45.14 µg/L) and tested positive for the c-KIT D816V mutation. Four out of five patients had an indolent lymphoma and were managed with a watch-and-wait approach. One patient experienced disease progression (Waldenstrom’s macroglobulinemia) requiring treatment with Rituximab and Bendamustine, achieving complete remission; bone marrow re-evaluation showed persistence of mastocytosis. Our case series confirms that the association between mastocytosis and lymphoproliferative disorders is rare and typically presents with indolent features. The mastocytosis component tends to have a favorable clinical course, regardless of the progression or remission status of the associated lymphoma.