In general lymphoblasts may vary from very small blasts (with a high nucleus-cytoplasm ratio) with very dense chromatin, indistinct nucleoli and scant basophilic cytoplasm, to larger blasts with more finely dispersed chromatin, prominent nucleoli and a moderate amount of light blue cytoplasm. Nuclei can be round, irregular or convoluted, vacuolisation can be present. Granules are rarely present.
B-ALL and T-ALL are indistinguisable by morphology.
Flow cytometry in general: CD45+(weak), cyCD3+, CD7+; CD34, surfCD3, CD2, CD5, CD4, CD8, CD1 & CD10 depending on subtype.