The clonality of dendritic cell proliferations arising in patients with previously diagnosed B-cell non-Hodgkin lymphoma has not been determined. The highly polymorphic human androgen receptor gene (HUMARA) can be used to assess the pattern of X-chromosome inactivation and, hence, the clonality of tumors in female patients. In this study, specimens from 2 female patients with dendritic cell tumor following low-grade B-cell non-Hodgkin lymphoma were analyzed. Microdissection was performed on tissue sections to obtain representative tissues for analysis. The HUMARA polymerase chain reaction was modified to include a fluorochrome (6-carboxyfluorescein)-labeled primer so the product could be assessed with the ABI Genescan Analysis program for the Macintosh (Applied Biosystems, Foster City, Calif). Our results indicate that dendritic cell proliferations associated with low-grade B-cell non-Hodgkin lymphoma are clonal lesions. Previous microdissection is very helpful in obtaining the desired cell populations for study. The use of a fluorescent primer coupled with the Genescan System is a novel, highly sensitive, quantitative system that avoids the use of radioactive materials.