Dermatoscopic Profiling of Inverted Follicular Keratosis in Differing Skin Phenotypes.

Abstract

Inverted follicular keratosis is a rare benign tumor of the follicular infundibulum. Due to its similarity to other benign and malignant cutaneous lesions, it poses a diagnostic challenge. There is limited information regarding the dermatoscopic characteristics of inverted follicular keratosis, and the majority of cases have been reported in patients with fair skin types. To describe the prevalent dermatoscopic features of inverted follicular keratosis, especially in patients with skin of color. We retrospectively analysed 35 histopathologically verified cases of inverted follicular keratosis fom a single university hospital in Turkiye. With respect to Fitzpatrick skin phototype, 2 (5.7%), 12 (34.3%), 16 (45.7%) and 5 (14.3%) patients had phototypes 2,3,4, and 5, respectively. Clinically, the majority of inverted follicular keratoses were hypopigmented or nonpigmented (82.9%). Pink-white structureless areas (54.3%), ulceration (54.3%), central keratin mass (42.9%), and blood spots on keratin mass (42.9%) were the most frequent dermatoscopic findings. Pigmented structures were observed as blue-grey structureless areas in 12 lesions and as blue-grey clods in 5 lesions, primarily in Fitzpatrick's phototypes 4 and 5. The incidence of a pink, structureless area and blood spots on ulceration was found to be statistically significantly higher in individuals with fair skin types, while a greater prevalence of blue-grey coloration was observed in those with skin of color (p < 0.05). Although our study presents some dermatoscopic distinctions of inverted follicular keratosis, the diagnosis is generally confirmed by histopathology, as the clinical appearance and dermatoscopic findings may not be sufficient to differentiate it from other tumors, especially squamous cell carcinoma or keratoacanthoma. The dermatoscopic characteristics of dark skin are comparable to those of pale skin; however, hyperpigmentation can be more noticeable in skin of color.