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.