A woman of 18 years of age consulted with a 7-year history of a recurrent preauricular tumor. The tumor decreased in size with oral antibiotic therapy, although it recurred frequently, without fever or suppuration. On physical examination there was a pink-colored tumor of 1.5cm diameter with a rubbery consistency. The tumor was situated adjacent to an orifice in the left preauricular region (Fig. 1). Skin ultrasound revealed a lesion with a heterogeneous, hypoechoic, particulate content, with solid deposits in its basal region and posterior enhancement (Fig. 1A, longitudinal section, B mode, 18Mhz). The lesion was continuous with a sinus tract running towards the depression adjacent to the auricle of the ear (Fig. 1B), beneath which there was an oval lesion measuring 0.75×0.33cm. This lesion had a hyperechoic center with an anechoic halo, compatible with a reactive lymphadenopathy (marked by an asterisk in Fig. 1B). Doppler mode revealed peripheral blood vessels around the lesion, related to the inflammation (Fig. 1C). The diagnosis was congenital preauricular fistula complicated by abscess formation. Treatment was started with doxycycline 100mg/d prior to surgery. Preauricular fistula is a rare benign congenital malformation that can present as an isolated finding, as in this case, or it may be associated with other congenital abnormalities. Skin ultrasound is very useful to confirm the diagnosis and differentiate the lesion from other diseases such as epidermal cyst and pilomatrixoma.

Figure 1.

Pink-colored left preauricular tumor adjacent to an orifice. A, Hypoechoic lesion with basal deposits and posterior enhancement. B, The lesion was continuous with a sinus tract, beneath which was an oval lesion with a hyperechoic center and anechoic halo (*). C, Blood vessels in the periphery of the lesion observed in Doppler mode.

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