Mast cell neoplasm: a challenging pathological diagnosis

Area of Science:

• Hematology
• Oncology
• Pathology

Background:

• Systemic mastocytosis (SM) is a rare myeloid neoplasm involving abnormal mast cell accumulation.
• Physician unfamiliarity and rarity contribute to diagnostic delays.
• Clinical presentation and disease course in SM are highly variable.

Purpose of the Study:

• To describe the clinicopathological features of mast cell neoplasms in a Brazilian cohort.
• To emphasize diagnostic pitfalls and morphological variants of SM.
• To assess the feasibility of diagnosing SM with limited resources.

Main Methods:

• Retrospective analysis of 12 patients diagnosed with mast cell neoplasm across three institutions.
• Review of morphological features, clinical findings, and immunohistochemical markers (CD117/C-KIT).
• Analysis of C-KIT mutational status and chromosomal abnormalities.

Main Results:

• The study included 12 patients (mean age 51.6 years), with 10 classified as aggressive SM.
• Common findings included anemia (9 patients) and bone marrow involvement (11 patients).
• Five distinct morphological patterns were identified, with mast cell aggregates being most frequent. CD117/C-KIT positivity was universal; mutations like D816V were detected in some cases.

Conclusions:

• Diagnosis of mast cell neoplasms is achievable using morphology and basic immunohistochemistry, even with limited resources.
• Pathologists must recognize diverse morphological variants and utilize appropriate markers for accurate SM diagnosis.
• Understanding diagnostic pitfalls is crucial for timely and correct identification of systemic mastocytosis.