The diagnostic utility of immunophenotyping and immunogenotyping in the pathologic evaluation of lymphoid proliferations.

One hundred eighty-two specimens of suspected lymphoma and lymphocytic leukemia were examined by morphology, immunophenotype, and immunogenotype (genotype) in order to answer the following questions: How often and in what situations does immunophenotyping help resolve a diagnostic problem that is not resolved by morphology? How frequently does genotyping help resolve a diagnostic problem that is not resolved by morphology and immunophenotyping? Of 182 cases for which fresh tissue was available, sixty-five cases were considered morphological diagnostic problems: There were 32 cases of neoplasia versus non-neoplastic proliferation, 16 cases of neoplasia with undifferentiated or ambiguous morphology, and 17 cases of lymphoma or lymphocytic leukemia with an uncertain subtype. Immunophenotyping helped to resolve 33 of these 65 cases. Of the remaining 32 cases genotyping helped to resolve the diagnosis in 16. These results suggest that immunophenotyping may diagnose approximately 50% of those cases which present a morphological problem, and that genotyping is also helpful in a limited but significant number of problem cases.