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A 45-year-old man presents for evaluation of a growth below his lower lip that is gradually increasing in size. The patient first noticed the lesion several months ago and, although it is asymptomatic, it is frequently traumatized when shaving. He denies having similar lesions elsewhere on his body and states that several years ago he was treated by a podiatrist for a plantar wart that resolved fully. Physical examination reveals a flesh-colored, slightly raised papule with peripheral pigmentation and slight scale.
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A biopsy of the lesion was performed, and histologic examination revealed an inverted follicular keratosis (IFK). IFK is an uncommon benign tumor that arises from the follicular infundibulum. The lesion classically presents as a solid, white to pink, hyperkeratotic plaque or papule.1 Lesions are most often found in middle-aged to elderly men and will typically arise on the head and neck. Clinically, IFK lesions may mimic other keratinizing proliferations such as viral warts and seborrheic keratoses, or malignancies such as squamous cell carcinoma, basal cell carcinoma, and melanoma.2,3
Diagnosis is confirmed by histopathology, although the diagnostic process may be assisted by certain dermoscopic findings such as a keratoacanthoma-like pattern comprising centralized keratin that is surrounded by hairpin vessels with a white halo.4 The etiology and pathophysiology of IFK remain largely unknown; the lesions share similarities with seborrheic keratoses, human papillomavirus, and viral warts.5 The presence of multiple IFKs may be a marker of Cowden syndrome.1,5
Recurrence of IFK lesions has been noted following incomplete surgical excision.3 Imiquimod cream may be an effective alternative to surgery.6 Neither invasive growth nor metastasis have been reported with IFK.3,6
Nelson Maniscalco, DPM, is a joint podiatry/dermatology fellow under the aegis of St. Luke’s Medical Center in Allentown, Pennsylvania, and the DermDox Center for Dermatology. Stephen Schleicher, MD, is director of the DermDox Center for Dermatology, associate professor of medicine at Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.
References
1. Shah R, Maddukuri S, Patel S, Behbahani S, Skula S, Lambert WC. Inverted follicular keratosis: stand-alone entity or variant. Skinmed. 2019;17(2):93-94.
2. Armengot-Carbo M, Abrego A, Gonzalez T, et al. Inverted follicular keratosis: dermoscopic and reflectance confocal microscopic features. Dermatology. 2013;227(1):62-66.
3. Thom GA, Quirk CJ, Heenan PJ. Inverted follicular keratosis simulating malignant melanoma. Australas J Dermatol. 2004;45(1):55-57.
4. Llambrich A, Zaballos P, Taberner R, et al. Dermoscopy of inverted follicular keratosis: study of 12 cases. Clin Exp Dermatol. 2016;41(5):468-473.
5. Chauhan A, Sharma N, Gupta L. Inverted follicular keratosis: a rare lesion revisited. Muller J Med Sci Res. 2017;8(2):86-87.
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.
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