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A 69-year-old man is referred for evaluation of a facial growth. He states that the lesion has been present for approximately 18 months and has not bled or caused other discomfort. His medical history is significant for rosacea, chondrodermatitis nodularis helicis, and actinic keratoses as well as ample past sun exposure. He does not smoke and drinks in moderation. Physical examination reveals a 0.5-cm slightly erythematous papule with a hyperkeratotic center.
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Inverted follicular keratosis is an uncommon benign tumor of the follicular infundibulum that was originally described by Helwig in 1954.1 It often appears as an asymptomatic solitary nonpigmented verrucous papule less than 1.0 cm in diameter on the face or neck. Elderly men are believed to be primarily affected with inverted follicular keratosis, although a recent analysis of periocular lesions found that the majority of patients with inverted follicular keratosis are women.2 The pathogenesis of this condition is unknown; the growth has been associated with human papillomavirus infection, seborrheic keratosis, viral warts, and Cowden syndrome.3
Diagnosis is made by histopathologic examination as the clinical appearance can resemble viral warts, basal cell carcinoma, and squamous cell carcinoma. Keratinization, when present, is minimal in comparison to the typical keratin-filled microcavity or horn cyst of seborrheic keratosis or the parakeratotic microcavity (pearl) of squamous carcinoma.4 The classic histopathologic sign is squamous eddies, which are tight whorls of bland appearing squamous cells that are created by irritated keratinocytes.5
Surgical excision is curative. Neither invasive growth nor metastases have been reported with this condition.2 A case report documents resolution of the lesion following therapy with topical 5% imiquimod cream.6
Alexandra Stroia, BS, is a medical student at the Lake Erie College of Osteopathic Medicine in Erie, Pennsylvania; Stephen Schleicher, MD, is director of the DermDox Dermatology Centers, associate professor of medicine at Geisinger Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.
References
1. Helwig EB. Inverted follicular keratosis. Paper presented at: American Society of Clinical Pathologists, International Congress of Clinical Pathology; September 1954; Washington, DC.
2. Díez-Montero C, González González D, Pérez Martínezi E, Schellini S, Galindo-Ferreiro A. Periocular inverted follicular keratosis: a retrospective series over 17 years. Jpn J Ophthalmol. 2019;63(2):210-214. doi:10.1007/s10384-018-00650-7
3. Ruhoy SM, Thomas D, Nuovo GJ. Multiple inverted follicular keratoses as a presenting sign of Cowden’s syndrome: case report with human papillomavirus studies. J Am Acad Dermatol. 2004;51(3):411-415. doi:10.1016/j.jaad.2003.12.049
4. Santa Cruz DJ, Gru AA. Tumors of the skin. In: Christopher F, ed. Diagnostic Histopathology of Tumors. 5th ed. Elsevier; 2021:1762-1918.
5. Ray A, Panda M, Samant S, Mohanty P. A rare case of inverted follicular keratosis in an elderly male: dermoscopic and histopathological overview with therapeutic response to imiquimod. Indian J Dermatol Venereol Leprol. 2021;87(3):455. doi:10.25259/IJDVL_224_20
6. Karadag AS, Ozlu E, Uzuncakmak TK, Akdeniz N, Cobanoglu B, Oman B. Inverted follicular keratosis successfully treated with imiquimod. Indian Dermatol Online J. 2016;7(3):177-179. doi:10.4103/2229-5178.182354
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