INVERTED FOLLICULAR KERATOSIS: A RETROSPECTIVE ANALYSIS OF 50 CASES

Background:  Inverted  follicular  keratosis  (IFK) is a rare benign skin neoplasm that could be diffcult  to  diagnose.  Pathomorphological  verifcation is recognized as the main diagnostic method. Aim: To analyze retrospectively clinical data from 50 IFK cases and to identify morphological tumor characteristics depending on its histological type. Materials and methods: Based on data extracted from medical documentation and reports on skin biopsies from 50 IFK patients, we analyzed retrospectively  some  clinical  data  and  pathohistological characteristics of IFK. We investigated pathohistological particulars of the tumor, identifed its histological  types  and  the  main  morphological signs of the neoplasm. We assessed the following histological  criteria  of  IFK:  presence  and  degree of  inverted  structures,  hyperkeratosis,  parakeratosis,  lymphoid  infltrates  in  the  derma.  Results: The  majority  of  IFK  patients  were  women  (68%) of older age (61.5± 1.6 years). In 40% of cases the tumor was located on the head, mostly on the face (32%); less frequently on the skin of the back (12%) and shanks (12%). At histological assessment, most cases (88%) of IFK were of one type. The most frequent  were  papillomatous  (32%),  keratoacanthomatous  (26%)  and  solid  (20%)  histological  types. Inverted structures were found in all histological preparations  (100%  of  cases).  Epidermal  abnormalities were mostly seen as hyperkeratosis (94% of  cases),  parakeratosis  (84%),  acanthosis  (78%) and dermal lymphoid infltration (74%). Advanced dermal  vascularization  was  seen  only  in  keratoacanthomous  and  cystic-keratoacantomous  histological types (76.9 and 100% of cases) and was characterized  by  reactive  proliferation  of  dermal capillaries. Conclusion: Pathomorphological verifcation of IFK is based on identifcation of inverted structures in bioptates. The variety of histological manifestations of the tumor is to be explained by various types of cell diferentiation.