Nonclonal lymphocytic proliferation in cutaneous lymphoid hyperplasia: a flow-cytometric and morphological analysis

Cutaneous lymphoid hyperplasia, follicular B cell pseudolymphoma or lymphadenosis benigna cutis and lymphocytic infiltration of Jessner-Kanof are a group of benign lymphoid hyperplastic disorders which usually involve the skin of the face or head and neck. These lesions may be difficult to differentiate from malignant lymphocytic lymphomas both morphologically and clinically. To evaluate whether quantitative flow-cytometric analysis and DNA ploidy determination of the lymphoid cells in the lesions would provide additional and more precise diagnostic parameters, we have correlatively analyzed a case by morphological, flow-cytometric and immunohistochemical methods. The two latter methods both revealed that the lesions harbored nonclonal heterogeneous subpopulations of lymphoid cells, but 62% of the cells analyzed were of B cell lineage progenies. No pre-B cells, immature B or T determinants were detected. Ploidy analysis of the isolated lymphocytes disclosed predominantly diploid (2 N) cells with about 1% 4 N and a few (less than 5%) hyperdiploid (2.2 N) cells. Cell cycle analysis showed that 97.2% of the cells were in G0-G1 phase. Phenotyping and DNA ploidy study of the lymphocytes of the lesion may provide quantitative diagnostic parameters to distinguish this benign lesion from true lymphocytic lymphoma involvement of skin. The eventual biological behavior of the minor hyperdiploid subpopulation of lymphoid cells found in this lesion is currently uncertain, however.