Accessory tragus is a fairly common congenital malformation of the external ear. However, it is extremely difficult to make a distinction between accessory tragus without cartilage and hair follicle nevus. Hair follicle nevus is an extremely rare adnexal hamartoma with follicular differentiation that commonly presents as a nodule on the face. Report of a Case A 2-month-old Japanese boy presented with an elastic, soft, pedunculated, hairy, light brown papule, 3 mm in diameter, that had been on the right preauricular area since birth (Figure 1). His family history was noncontributory. The lesion was diagnosed as accessory tragus, excised, and examined histologically. Hematoxylin-eosin stains showed the crowding of many tiny mature hair follicles in different stages in the dermis (Figure 2). Several sebaceous glands connected with the hair follicle, and there was abundant fat and a few eccrine glands. Serial sections revealed no cartilage and no central dilated infundibulum, excluding the possibility of trichofolliculoma. View LargeDownload Figure 1. A pedunculated papule. A, Clinical findings of a pedunculated papule in the right preauricular area. B, A close-up view of the papule (3 × 3 mm). View LargeDownload Figure 2. Histopathologic findings of the right preauricular papule. Tiny mature hair follicles in different stages in the dermis (hematoxylin-eosin, original magnification ×40). Comment Accessory tragus is a congenital lesion that typically appears as solitary, pedunculated, flesh-colored papules located between the pretragal and sternoclavicular areas. Clinical diagnosis as accessory tragus is based on its location and the time of appearance. Histopathologic features of accessory tragus have been reported to be characterized by numerous telogen follicles, abundant lobules of fat, and a central core of cartilage.1 However, the absence of cartilage in accessory tragus is not necessarily uncommon.2,3 When no cartilage is found, it is necessary to consider the relationship with hair follicle nevus. Hair follicle nevus is an extremely rare adnexal hamartoma with follicular differentiation. It is often congenital, characterized histologically by many tiny mature hair follicles, and is typically located on the face. The differential diagnoses include accessory tragus, trichofolliculoma, and hair nevus. In particular, controversy exists about the histologic differences between hair follicle nevus and accessory tragus. Satoh et al2 stated that a prominent connective tissue framework in subcutaneous fat was found in accessory tragus, but not in hair follicle nevus, regardless of the presence of cartilage. Ban et al4 pointed out that the number of fat cells in the nodules or papules differed between the 2 conditions, with scant fat cells in hair follicle nevus. Our case seems to be more suitable for the diagnosis of accessory tragus based on the location, the time of appearance, and the abundance of fat cells, but it is also consistent with the clinical and histological features of hair follicle nevus. This case exhibits a close relationship between these 2 disease entities. Hair follicle nevus may be incomplete accessory tragus.4 Germain et al5 and Asahina et al6 proposed the concept that accessory tragus and hair follicle nevus are basically within the same spectrum of hamartoma, although the developmental mechanism may differ according to the component or location. To our knowledge, 28 cases, including our case, of hair follicle nevus have been reported either in textbooks or the literature. These include some located on the preauricular area, as was observed in our case. Our data support the hypothesis that accessory tragus and hair follicle nevus are within the same spectrum of hamartoma. Back to top Article Information Correspondence: Dr Kotaro Nagase, Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga 849-8501, Japan (firstname.lastname@example.org). Financial Disclosure: None reported. Additional Contributions: We are indebted to the generous patient who made this report possible. References 1. Brownstein MH, Wanger N, Helwig EB. Accessory tragi. Arch Dermatol. 1971;104(6):625-6315131708PubMedGoogle ScholarCrossref 2. Satoh T, Tokura Y, Katsumata M, Sonoda T, Takigawa M. Histological diagnostic criteria for accessory tragi. J Cutan Pathol. 1990;17(4):206-2102394863PubMedGoogle ScholarCrossref 3. Sebben JE. The accessory tragus: no ordinary skin tag. J Dermatol Surg Oncol. 1989;15(3):304-3072646335PubMedGoogle ScholarCrossref 4. Ban M, Kamiya H, Yamada T, Kitajima Y. Hair follicle nevi and accessory tragi: variable quantity of adipose tissue in connective tissue framework. Pediatr Dermatol. 1997;14(6):433-4369436838PubMedGoogle ScholarCrossref 5. Germain M, Smith KJ. Hair follicle nevus in a distribution following Blaskho's lines. J Am Acad Dermatol. 2002;46(5):(Suppl) S125-S12712004289PubMedGoogle ScholarCrossref 6. Asahina A, Mitomi H, Sakurai N, Fujita H. Multiple accessory tragi without cartilage: relationship with hair follicle naevi? Acta Derm Venereol. 2009;89(3):316-31719479139PubMedGoogle ScholarCrossref
Archives of Dermatology – American Medical Association
Published: Feb 1, 2012
Keywords: infant,papule,hair follicle nevus
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