Disease:
General detection of B cells/B cell origin (with CD20);
In ALL or small B cell lymphoproliferative disorders when CD20 may be negative,
In infarcted lymphomas, differentiate preB lymphoblastic lymphoma from Ewing’s sarcoma

Also called MB-1, B cell antigen receptor complex associated protein alpha-chain
Encodes Ig-alpha protein of the B cell antigen receptor; the receptor also includes Ig-beta protein (CD79b) and surface immunoglobulin
Expressed early in B cell differentiation (often positive when mature B cell markers are negative); also expressed in plasma cells
In AML, presence usually represents aberrant B cell antigen in leukemias of distinct myeloid linage, not biphenotypic differentiation
CLL patients have low B cell-IgM surface expression due to defects in glycosylation and folding in µ and CD79a chains

Collection:
FFPE/un-stained slides/Fresh tissue in formalin

Stability:
Room temperature

Unacceptable Conditions:
Unlabeled specimen/specimen left unfixed
for extended periods