Circumscribed sebaceous gland hyperplasia: autoradiographic and histoplanimetric studies.

Circumscribed sebaceous gland hyperplasia (sebaceous hyperplasia) is a common benign facial tumor found in adults and aged. Seventeen biopsies of sebaceous hyperplasia from 10 patients, females and males aged 57-87 years were secured which were injected 45 min or up to 15 days prior with tritiated thymidine, and prepared for autoradiography. Specimens were evaluated by cell counts (labeling index, labeled total cells), and histoplanimetric techniques (sagittal section areas and circumference of sebaceous hyperplasia, of sebocytes, and of sebocyte nuclei). Controls were uninvolved sebaceous follicles from the same subjects, from an age-matched group, and from young male adults. In sebaceous hyperplasia the labeling index of basal cells is low with 5.7% +/- 2.3 vs uninvolved sebaceous follicles from the same subject (8.6% +/- 2.4) and the younger subjects with a value of 10.1% +/- 2.0). Labeled cells are retained in the acini much longer than in young adults (slowed down transit and turnover time). The glands of sebaceous hyperplasia are very large, their sebocytes are small, and many more basal cells are found per unit basement membrane length.