First branchial apparatus anomalies presumably arise from incomplete closure during early embryological development.1They may present as cysts, sinuses, or fistulas.2Work3described the classification of such anomalies, dividing them into types I and II. Type I anomalies classically consist of aberrant duplications of the membranous portion of the external auditory canal, are preauricular and lateral to the facial nerve, and are composed entirely of ectodermal tissue. Type II anomalies are located more inferiorly, may track medial to the facial nerve toward the bony-cartilaginous junction of the external auditory canal, and can include tissue of both ectodermal and mesodermal origin.4Pathologically, first branchial apparatus anomalies demonstrate squamous epithelium lining the cyst wall and, in the case of type II lesions, variable ectodermal components, including adnexal structures and mesodermal tissue.3The first pathologic report of such a lesion, with findings remarkably similar to our index case, was published in 1908.5
Pathology Quiz Case 3: Diagnosis. Arch Otolaryngol Head Neck Surg. 2011;137(4):415. doi:10.1001/archoto.2011.50-b
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