Histologic and immunophenotypic features of lymphoblastic lymphoma. A-J, T-cell lymphoblastic lymphoma shows sheets of monotonous medium-sized blasts with round, oval or irregular nuclei, granular nuclear chromatin, frequent mitotic and apoptotic figures (A, H&E-stained touch imprint; B, H&E-stained section), positivity for CD3 (C), TdT (D) and CD99 (E) by IHC; and positivity for CD45 , CD4, CD8, CD1a, CD7 , CD2, CD5, TdT and cytoplasmic CD3 by flow cytometry (FCM) (F-J). K-T, B-cell lymphoblastic lymphoma shows similar cytomorphology (K, H&E stain), positivity for TdT (M), CD10 (N) and PAX5 (O), and negativity for CD3 (L) by IHC; positivity for CD19, CD10, CD38 and CD34, and negativity for CD45, CD20, CD33, kappa and lambda by FCM (P-T).