Proliferating Pilar Tumors: Can Immunohistochemistry Differentiate Benign and Malignant Forms?

BACKGROUND Proliferating pilar tumor (PPT) is an adnexal tumor of purported differentiation toward the follicular outer root sheath. Immunohistochemistry has been suggested to differentiate between benign and malignant forms. METHODS Eleven benign (PPT) and 9 malignant PPT lesions were reviewed; Ki67, p27, and p53 were applied. The staining intensity (strong, moderate, weak, and negative), positive cell numbers, and marker indexes (%) were scored using image-analysis software (ViraSoft). RESULTS Overall, there was no significant correlation between Ki67 and p53 and histopathological features. However, malignant PPTs had significantly lower numbers of p27-positive cells (P = 0.030). CONCLUSIONS Our study includes the largest group of patients in whom image analysis of p53, Ki67, and p27 has been used to try to separate benign from malignant lesions. Although there were no significant differences regarding Ki67 and p53, malignant lesions have a statistically lower expression of p27. Further studies may be needed to determine the clinical usefulness of image analysis in this differential diagnosis.