It is possible to diagnose systemic mastocytosis through basic morphology and a restricted immunohistochemical panel, according to a new study published in the journal Human Pathology

“Of note, pathologist(s) should recognize the different morphological variants of the disease and include the adequate markers when requesting immunohistochemical studies,” the authors of the study wrote.

It is difficult to diagnose systemic mastocytosis because it is so rare and most physicians are not familiar with it.

Read more about the diagnosis of systemic mastocytosis.

Here, a team of researchers from Brazil led by José Vassallo, MD, conducted a retrospective study on 12 patients, aged 15 to 81 years, diagnosed with mast cell neoplasm. Of these, 10 had aggressive systemic mastocytosis, 1 had systemic mastocytosis with an associated acute promyelocytic leukemia, and 1 had mast cell sarcoma. 

The most common clinical findings were anemia seen in 9 patients, thrombocytopenia seen in 3 patients, and skin lesions also seen in 3 patients. Bone marrow involvement occurred in 11 patients at the time of diagnosis. In 5 patients the skin was also involved. 

There were 5 histological patterns. These were: mast cell aggregates, plasmacytoid, monocytoid, spindle cell, and epithelioid/pleomorphic morphology. Of the 12 patients, 2 showed 2 histological patterns. 

All neoplastic cells were positive for CD117/C-KIT. Four patients had the C-KIT D816V mutation, 2 had the C-KIT K509I mutation, and 1 patient had the del(7q22) mutation. No mutational status was available for the remaining 5 patients.

“Despite limited resources, basically morphology and a restricted immunohistochemical panel, it is possible to diagnose mast cell neoplasm,” the researchers concluded.

Systemic mastocytosis is a disease in which neoplastic mast cells grow abnormally and accumulate in at least one extracutaneous site. The clinical presentation and course of the disease vary greatly among patients with some having indolent disease and others developing an aggressive, leukemic form of the disease.


Natal RA, Carvalho HC, Barra FFC, Pagnano BKB, Soares FA, Vassallo J. Mast cell neoplasm: a challenging pathological diagnosis. Hum. Pathol. Published online May 10, 2022. doi: 10.1016/j.humpath.2022.05.007