Aggressive systemic mastocytosis mimicking lymphoma: a case report

Background: Aggressive systemic mastocytosis (ASM) is a very rare form of systemic mastocytosis (SM). The diagnosis of ASM requires the presence of SM criteria with C finding and does not meet the criteria for mast cell leukaemia. Herein, we report an ASM case that initially mimicked lymphoma based on clinical and radiographic analyses. Case presentation: A 87-year-old woman was admitted to our hospital due to the enlargement of cervical lymph nodes and weight loss. The lymph node biopsy is infiltrated by neoplastic mast cells with pale, faintly granular cytoplasm, and with reactive eosinophils in the lesions. The infiltrate is often parafollicular in distribution and the remnant of normal follicles can be seen. The neoplastic cell population was subsequently revealed to exhibit differentiation towards the mast cell lineage by expressing CD117 and CD25. Mutation analysis of c-KIT identified D816V mutation in exon 17. Conclusion ASM diagnosis can be challenging due to its rarity. This diagnosis can be confirmed or disregarded using immunohistochemical markers, such as CD117, CD2 and CD25, in combination with molecular analysis (KITD816V).