Adult teratoma manifested as a lateral neck mass

An adult neck mass with atypical clinical presentation can pose diagnostic challenge with a large list of differential diagnosis. Here, we present a case of an adult lateral neck mass with challenging preoperative diagnosis, that was turned out to be an exceptionally rare case of adult neck teratoma. 54-year-old male presented with a soft and elastic egg-size mass of the left neck. His vitals and blood tests were unremarkable. Ultrasonography, computed tomography scan and MRI demonstrated a cystic mass with solid heterogeneous component including adipose tissue. Fine needle aspiration of the mass yielded purulent viscous content, but bacterial cultures including Mycobacterium were negative. Cytology showed squamous cells without atypia. Together, preoperative differential diagnosis included neurogenic tumors, teratoma, as well as congenital disorders such as thyroglossal duct cyst and branchial (cleft) cyst. Postoperative microscopic examination revealed various mature tissues, including stratified squamous epithelium with keratin debris and sebaceous gland, adipose, chondroid, and pancreatic acinar tissues, without immature components. Taken together, pathological diagnosis of neck mature teratoma was made. Urological examination did not reveal testicular tumors, further corroborating the diagnosis. The patient was discharged without postsurgical complications. Teratoma, a rare germline cell tumor containing various types of tissues and organs, typically affects genital organs, mediastinum and retroperitoneum. However, a neck teratoma, especially in adult, is exceptionally rare. Although not common in frequency, a teratoma can be a challenging differential diagnosis of an adult neck mass.