Large cell anaplastic lymphoma: evaluation of immunophenotype on paraffin and frozen sections in comparison with ultrastructural features.

Eleven cases of large cell anaplastic lymphoma (T type n = 5, B type n = 4, 0 type n = 2) were investigated using electron microscopy and immunophenotyping on formalin-fixed paraffin sections and frozen sections of fresh tissue, to determine whether morphological criteria exist for the discrimination of T, B, and 0 phenotypes. Tumour cell lineage could not be established from ultrastructural features. On paraffin material monoclonal B-cell markers Ki-B5 and L-26 served as reliable tools for recognizing the B phenotype of large cell anaplastic lymphomas (previously determined on fresh material). whereas monoclonal antibodies MT1 (CD43) and UCHL1 (CD45RO) were of limited value in lineage determination.