Abstract
BackgroundMast cell leukemia (MCL) is a very rare form of systemic mastocytosis (SM) and accounts for less than 0.5% of all mastocytosis. The diagnosis of MCL requires the presence of SM criteria, accompanied by leukemic infiltrating of atypical mast cells (MCs) in bone marrow (BM), peripheral blood as well as extracutaneous organs. MCL is a fatal disease that almost always behaves aggressively, and the median survival time is only about six months. Herein, we present a rare case of de novo MCL without CD25 expression and KIT mutations.Case presentationA previously healthy 13-year-old boy was referred to our hospital due to incidental discovery of an enlarged right tonsil. Diffuse infiltration of medium-sized hematopoietic blasts was found in his right tonsil, BM and multiple lymph nodes. The neoplastic cell population was subsequently revealed to exhibit differentiation towards the mast cell lineage by expressing CD117 and tryptase, but the cell population lacked expression of CD25/CD2 and the activating mutation of the KIT gene. An abnormal karyotype was identified, but no leukemia-associated fusion genes were found. Involvement of peripheral blood, bone and lung was subsequently demonstrated. The most important differential diagnosis included tryptase-positive (T+) acute myeloid leukemia, myelomastocytic leukemia and basophilic leukemia. The morphological characteristics and infiltrating patterns of the abnormal MCs supported the final diagnosis of MCL. Although intensive chemotherapy and allogeneic stem cell transplants were performed on the patient, he died 18 months after initial presentation.ConclusionDue to its rarity, the diagnosis of MCL without typical immunophenotype and genetic aberrations is particularly challenging. Comprehensive investigation of clinical and pathological features to exclude other T+ myeloid neoplasms is necessary.
Highlights
Mast cell leukemia (MCL) is a very rare form of systemic mastocytosis (SM) and accounts for less than 0.5% of all mastocytosis
Mastocytosis, the most well-known disease derived from mast cells (MCs), presents as a heterogeneous group of diseases characterized by clonal proliferation of MCs in various organ systems
We report an unusual case of de novo leukemic MCL without expression of CD25 and KIT mutations, which initially raised the suspicion of tryptase-positive (T+) acute myeloid leukemia (T + Acute myeloid leukemia (AML)) or myelomastocytic leukemia (MML)
Summary
Mast cells (MCs) are defined as a type of leukocytes derived from hematopoietic stem cells, which contain abundant cytoplasmic basophilic granules rich in various mediators, such as serine proteases, and play a key role in innate and adaptive immunity [1]. Mast cell leukemia (MCL), one of the rarest types of leukemia, is the leukemic form of SM that accounts for less than 0.5% of all mastocytosis. We report an unusual case of de novo leukemic MCL without expression of CD25 and KIT mutations, which initially raised the suspicion of tryptase-positive (T+) acute myeloid leukemia (T + AML) or myelomastocytic leukemia (MML). The BM biopsy showed the normal architecture was almost completely replaced by atypical cells that shared similar immunohistochemical and molecular characteristics with the blasts in tonsils but shared differentiating features with immature MCs, such as medium-sized oval or spindle shaped nuclei. These atypical cells were positive for HLA-DR, CD56, CD33, CD117, BDCA-1, CD9, CD69, CD11c, and CD11b but were negative for CD34, CD123, CD25, CD2 and MPO by flow cytometry. He suffered from tumor dissemination, and died from cerebral hemorrhage almost 18 months after initial presentation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
