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An 80-year-old man presents to the clinic requesting the removal of a facial lesion, which has been increasing in size over the past several months. He was previously evaluated by a family practitioner who recommended that he use a topical over-the-counter wart-removing compound. The patient noted that the product caused irritation and he discontinued use. Physical examination reveals a crusted papule above the lip. Scattered seborrheic keratoses are also noted on his face and trunk.
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Inverted follicular keratosis (IFK) is an uncommonly encountered benign, slow-growing neoplasm that typically presents as an exophytic smooth or verrucous papule on the face. The lesion was first described in 19541 and was identified as arising from the infundibulum of the hair follicle several years later.2 Dermatoscopic findings may include radial peripheral hairpin vessels surrounded by a whitish halo.3
Diagnosis is made by biopsy with the exophytic portion manifested as an inverted, well-circumscribed lobule composed of basaloid and squamoid cells.4 The squamoid cells often contain clear cytoplasm. Histopathology may resemble verruca vulgaris and trichilemmoma.
The etiology of IFK is uncertain and lesions may represent a follicle-oriented irritated seborrheic keratosis or verruca.5 Most cases of IFK are solitary and shave excision is usually curative. Multiple lesions may be a marker for the autosomal dominantly transmitted Cowden syndrome, which is associated with internal malignancies.6
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, In: Seminar on the Skin: Neoplasms and Dermatoses. Presented at the American Society of Clinical Pathologists, International Congress of Clinical Pathology, Washington, DC, September 1954.
2. Mehregan AH. Inverted follicular keratosis. Arch Dermatol. 1964;89:229-235. doi:10.1001/archderm.1964.01590260067012
3. Armengot-Carbo M, Abrego A, Gonzalez T, et al. Inverted follicular keratosis: dermoscopic and reflectance confocal microscopic features. Dermatology. 2013;227(1):62-66. doi:10.1159/000351715
4. Ruhoy S. Inverted follicular keratosis. Dermatology Advisor. March 13, 2019. Accessed June 28, 2023. https://www.dermatologyadvisor.com/home/decision-support-in-medicine/dermatology/inverted-follicular-keratosis/
5. Hocker S, Rabinovitz HS, Oliviero M, Grant-Kels J, Scope A. Reflectance confocal microscopy of an inverted follicular keratosis mimicking a squamous cell carcinoma. Dermatol Pract Concept. 2017;7(4):39-42. doi:10.5826/dpc.0704a09
6. Larumbe A, Iglesias EM, IIIarramendi JJ, Córdoba A, Gállego M. Acral keratoses and inverted follicular keratosis presenting Cowden disease. Actas Dermosifiliogr. 2007;98:425-429.
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