CD2 and systemic mastocytosis: Several different staging investigations need to be performed from the BM in patients with SM including microscopic investigations on smears stained with Wright-Giemsa, histology and immunohistochemistry (IHC), cytogenetics, flow cytometry for documenting the expression of CD2 and/or CD25 on neoplastic MCs, and PCR to detect KIT D816V [3, 82].