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Temporal bone histopathology case of the month. First branchial cleft anomaly with an orifice in the bony external auditory canal accompanied by contralateral middle ear cholesteatoma.

First branchial cleft anomalies are rare. These anomalies are caused by incomplete fusion of the first cleft between the first and second branchial arches and occur at a frequency of approximately 1% to 10% among all branchial anomalies (1,2). The external auditory canal is derived from the first branchial cleft, and it is commonly accompanied by an orifice on the floor of the external auditory canal, either at the level of the bony-cartilaginous junction or in the cartilaginous portion (2). A first branchial cleft malformation sometimes accompanies an anomaly of the external ear canal or middle ear and cholesteatoma (1Y4). Here, we report a rare case of a first branchial cleft sinus orifice in the bony external auditory canal accompanied by contralateral middle ear cholesteatoma containing an aberrant bony structure. A 63-year-old woman presented with a right upper neck mass that developed rapidly within a few days. Although she reported episodes of swelling and purulent discharge from the area during her youth, she had been symptom-free for 45 years. There was no visible orifice on her neck, but scarring was noted. Her right tympanic membrane was partly atrophic without perforation, and there was an orifice in the bony external canal (Fig. 1A). Computed tomography (CT) scan showed that the orifice passed vertically through the temporal bone toward the upper neck (Fig. 1, B and C). Magnetic resonance imaging (MRI) revealed a cyst on the right side extending from the deep portion of the parotid gland to the parapharyngeal space (Fig. 1, DYF). The left tympanic membrane was perforated and accompanied by a cholesteatoma visible at the anteroinferior quadrant behind the annulus (Fig. 2, AYC). The patient was diagnosed with a right first branchial cleft sinus and a left middle ear cholesteatoma. After 6 months, she underwent excision of the right first branchial cleft sinus by a submandibular approach. The right submandibular gland was resected to visualize the parapharyngeal area. The first branchial cleft sinus was found to be connected to the bony external ear canal by a cartilaginous duct, whichwas ligated at the border between the bony canal and cartilaginous duct, and the sinus was resected. The duct passed medially to the facial nerve but did not cross it, and there was no indication of postoperative facial nerve palsy. Histologically, the sinus was composed of a lumen with stratified squamous epithelium connected to a cartilaginous tract (Fig. 3). One year after excision of the right first branchial cleft sinus, the left middle ear cholesteatoma was removed, and type 1 tympanoplastywas performed. All 3 ossicles were intact with good mobility. Histologically, the cholesteatoma contained bony tissue (Fig. 2D). There has been no recurrence as of 2 years after removal of the first branchial cleft sinus. The anterior and medial walls of the tympanic cavity are formed by the first branchial arch, whereas the floor of the tympanic cavity is formed by the second branchial arch (5). The borderline between the first and second branchial arches is a possible site of residual tissue of the first branchial cleft. Therefore, in our case, the cholesteatoma containing the bony structure was possibly an aberrant structure related to an anomaly of the contralateral first branchial cleft.