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KMID : 0363220170550070477
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Korean Journal of Dermatology
2017 Volume.55 No. 7 p.477 ~ p.478
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A Tender Fingertip Papule in an Elderly Woman
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Seok Joon
Oh In-Young
Park Kui-Young
Li Kapsok
Kim Beom-Joon
Seo Seong-Jun
Kim Myeung-Nam
Hong Chang-Kwun
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Abstract
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A 65-year-old Korean woman presented with a hyperkeratotic, firm, tender, and yellowish papule measuring 3 mm in diameter, which first appeared on the tip of her right thumb 2 months prior to presentation (Fig. 1A). She related a history of trauma at this site from an unknown sharp object at approximately the same time the lesion appeared. The lesion was clinically diagnosed as a foreign body reaction, excised with a skin punch, and examined histologically. Hematoxylin-eosin staining revealed that the wall of the cyst was lined with squamous cells, and the cavity was composed of keratinized lamellar material (Fig. 1B). We confirmed the diagnosis of an epidermal cyst on the distal tip of her thumb. Postoperative follow-up was unremarkable, without any complications or recurrence.
Epidermal cysts have been termed infundibular cysts, suggesting that they arise from the infundibular portion of the hair follicle. Therefore, these cysts most commonly occur on hair-bearing areas of the body such as the scalp, face, neck, trunk, and scrotum. Additionally, they may rarely occur following traumatic implantation of epidermal elements into the dermis particularly on the palms and soles1-3. Burial of tissue, a secondary proliferative response to blunt trauma, and inflammation have been described as possible pathomechanisms for the development of traumatic epidermal cysts4. Human papillomavirus (HPV) infections may play a role in causing epidermal cysts. Egawa et al. have reported a case wherein an HPV-associated epidermal cyst was observed to have developed following epidermoid metaplasia of the eccrine duct epithelium5.
Because our patient had a positive history of trauma with a sharp object, her cyst was clinically diagnosed as a foreign body reaction. Although histopathological examination revealed that it was an epidermal cyst, the precise mechanism of development of the cyst remains unclear. The time interval between the trauma and appearance of the lesion was too short for the growth of an epidermal cyst. Thus, we hypothesize that a traumatic or HPV-associated epidermal cyst already existed in this patient and subsequently increased in size following trauma, which acted as a trigger. Occurrence of epidermal cysts on fingers is extremely rare, and they can easily be misdiagnosed/confused with viral warts or calluses. Other differential diagnoses that should be considered for such lesions on the fingertip are ganglion cysts, mucous cysts, acquired digital fibrokeratomas, trichilemmal cysts, and glomus tumors6,7.
This case highlights an unusual clinical manifestation of an epidermal cyst at an unexpected location. To the best of our knowledge, this is the first case of a hyperkeratotic, firm papule on the fingertip of a patient, which was diagnosed as a traumatic epidermal cyst. It is important that dermatologists should perform a careful physical examination without assuming a clinical diagnosis to correctly diagnose and appropriately treat papular lesions of the fingers.
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KEYWORD
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Epidermal cyst, Fingertip
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