Salivary Duct Carcinoma of the Middle Ear: A Rare and Challenging Diagnosis

Abstract

Salivary duct carcinoma is an aggressive tumor, morphologically similar to high-grade ductal adenocarcinomas of the breast. Although most commonly involving the major salivary glands, approximately 10% of salivary duct carcinomas arise from the minor glands of the palate and oral cavity, with rare isolated cases reported as primary to the larynx, sinuses, and mandible. We present a case of a 53-year-old man with ear discomfort and left facial paresis. He had a 2-year history of chronic middle ear pain and presumed mastoiditis; prior biopsy of the auditory canal showed extensive granulation tissue and epithelial fragments suggestive of a middle ear adenoma. At the time of his most recent presentation, no lesions were radiographically seen within the parotid or submandibular glands. A focused MRI showed 2 foci in the left petrous apex that were consistent with cholesterol granulomas but no welldefined mass to correspond with the biopsy diagnosis of middle ear adenoma. Microscopically, the H&E-stained slides contained many oncocytic glands with a papillary and cribriform growth pattern and focal necrosis. Cytologically, the cells were enlarged with mild to moderate nuclear pleomorphism and scattered mitoses. Histochemical and immunohistochemical stains were performed on the paraffin embedded resection specimen. Mucicarmine stained intraluminal mucin. Cytokeratins (AE1/AE3, CAM5.2), CEA, androgen receptor, and GATA3 highlighted cells of interest. Her2 had weak membranous positivity. P63 marked rare abluminal cells and Ki67 (MIB-1) was <5%. The lesion was negative for chromogranin, synaptophysin, NSE, CK5, CK20, S100, GFAP, and TTF-1. Given the distinct staining pattern and histomorphology, the diagnosis was consistent with salivary duct carcinoma. To our knowledge, following a thorough review of current literature, this is the first case of salivary duct carcinoma to originate in the middle ear.

Salivary Duct Carcinoma in the External Auditory Canal Causing Ipsilateral Hearing Loss

“…SDC was first described in 1968 by Kleinsasser et al [2]. SDC typically involves the major salivary glands, but approximately 10% of all SDCs are diagnosed in the minor salivary glands, palate, and oral cavity [3]. Other primary sites are extremely rare [1,[3][4][5].…”