CLASSIFICATION OF T-CELL AND NK-CELL NEOPLASMS BASED ON THE REAL, CLASSIFICATION

Mature or peripheral T-cell lymphomas are uncommon, accounting for onl y 10%-15% of all non-Hodgkin's lymphomas. The classification of these neoplasms has been controversial. In contrast to B-cell lymphomas, cyt ologic grade has not been very useful in predicting the clinical cours e. This finding may result from the generally aggressive clinical cour se associated with T-cell lymphomas. Prior studies have suggested that stage of disease may be more important than cytologic subtype. Clinic al presentation is very important in the classification of T-cell mali gnancies. For T-cell lymphomas, cytologic features alone are not suffi cient to distinguish among disease entities. For example, adult T-cell leukemia/lymphoma (ATLL) often cannot be distinguished morphologicall y from HTLV-l-negative T-cell lymphomas. Most extranodal T-cell lympho mas appear to be derived from cytotoxic T cells, which express perfori n, TIA-1, and granzyme B. Three broad groups of T-cell malignancies ca n be identified: (1) leukemic or systemic disease; (2) nodal disease; (3) extranodal disease. Anaplastic large-cell lymphoma (ALCL) is proba bly the single most common subtype of T-cell lymphoma. Classical ALCL should be distinguished from primary cutaneous ALCL (CD30+ lymphoproli ferative disease of the shin), which is a distinct disease entity.