Myeloid Sarcoma : Breast
Myeloid Sarcoma of Breast: Microscopically, there is a diffuse infiltrate of medium to large mononuclear cells with effacement of normal architecture. The tumor cells have scant to moderate amounts of cytoplasm, finely dispersed chromatin, and punctate nucleoli. Immunophenotyping shows dim or negative CD45 and expression of myeloperoxidase, CD33, CD43, CD68 (KP1), CD117, TdT, and lysozyme. Lineage-specific B- and T-cell markers such as CD20 and CD3 respectively are absent. Rare cases may show aberrant expression of these markers or less specific ones such as B-cell associated PAX5 or T-cell associated CD7.