"Small cells" have been described in the cervical-vaginal (Papanicolaou [Pap]) smears of patients receiving tamoxifen. The current study determined the frequency of this finding and its implications for the differential diagnosis.
A computer-based search of the cytopathology files from January 1994 to December 1998 was performed for Pap smears from patients with a history of tamoxifen treatment. All smears were reviewed for the presence of "small cells" and endometrial cells. Pap smears from an age-matched control group that was not treated with tamoxifen also were screened for "small cells."
Five hundred forty-eight Pap smears were identified from 425 patients (mean age, 62 years; average duration of treatment, 43 months). Clusters of these "small cells" were present in 104 Pap smears from 86 patients (19%). The background pattern was proliferative in the majority of the Pap smears (83%). In five Pap smears (5%), these "small cells" were interpreted originally as endometrial cells. In the remaining Pap smears, no reference to the presence of the cells was made in the original report. "Small cells" were identified in 79 Pap smears (18%) in the control group (n = 443 smears).
The incidence of "small cells" is similar in the Pap smears of patients with or without a history of tamoxifen treatment. These cells are similar to reserve cells noted in atrophic smears. However, as a result of the proliferative effect of tamoxifen in the cervical epithelium, these cells are prominent when admixed with superficial and intermediate cells in patients treated with tamoxifen. These cells need to be differentiated from endometrial cells to avoid unnecessary follow-up procedures. Cancer (Cancer Cytopathol)