Clinicopathologic re-evaluation and of the tissue samples of hair follicle tumors in a 30-year period in Mashhad

Background and aim: The skin has some appendages that give origin to various tumors. These tumors are generally divided to pilosebaceous and sweat glands tumors according to embryologic and histological features. Clinical and histological characteristics of these tumors are also divergent. In addition, classification of them according to histological background has been changed considerably in recent years. The aim of this study is to asses the frequency and clinicoepidemiologic characteristics of these tumors based on re-evaluation of the tissue specimens by applying new histological criteria for a better understanding, experience and reclassification. Materials and methods: All tissue samples with a definite, differential, probable or uncertain diagnosis of any kind of skin appendage tumors, archived in Pathology Department of Imam Reza University Hospital of Mashhad, during the past 30 years (1976-2005) were elicited. All the specimens were reobserved histopathologically by applying new diagnostic criteria and if necessary, were recut and stained with H&E and special histochemical stains. Clinical data were gathered and presented in tables and charts and analyzed statistically by SPSS software. Results: From 134748 archived specimens, 444 appendageal tumors were found of which 161 were of follicular origin composed of 119 pilomatrixoma (73.9%), 19 trichoepithelioma (11.8%), 15 inverted follicular keratoses (9.3%), 4 proliferating pilar tumor (2.5%), 2 trichoblastoma (1.2%), 1 trichofolliculoma (0.6%) and 1 trichoadenoma (0.6%), with a mean age of 28 years in 71 men and 90 women. The most prevalent location was head and neck area (57.5%) and the most common presentation was a nodule (81%), mostly single (94%). In most cases previous pathologic diagnosis was confirmed (95.2%) and clinico-epidemiologic features were in accordance with other world wide reports, although some changes in tissue diagnosis and differences in clinico-epidemiologic features were noted. Conclusion: Hair follicular tumors are relatively uncommon tumors, mostly benign and occurring in youngs specially in head and neck. Some differences in clinico-epidemiologic features could be related to race, genetic background, environment and etc. Some mistakes in previous tissue diagnosis alarm the pathologist to pay special attention to the wide range of differential diagnosis and to employ definite histopathologic criteria regarding differences in patterns of involvement.