Salivary gland tumors account for less than 5% of head and neck neoplasms and typically present in the oral cavity . The likelihood of finding malignant rather than benign disease in a salivary gland tumor increases as the size of the gland of origin decreases . Salivary gland carcinoma accounts for less than 0.5% of all nasopharyngeal malignancies, likely owing to the low density of salivary gland tissue in the nasopharynx. Within the nasopharynx, adenoid cystic carcinoma is the most common salivary gland tumor, followed by adenocarcinoma .
Papillary serous adenocarcinoma is a histologically unique form of adenocarcinoma. This tumor is considered to be derived from nasopharyngeal surface epithelium rather than from underlying minor salivary glands, based on histological appearance and immunohistochemical staining profile. It is uncommon, occurring over a wide age range with no sex predilection. The commonest site is lateral or posterior wall or roof of the nasopharynx, and it presents as a soft to gritty mass with a nodular or papillary appearance. Despite a benign histological appearance, this tumor is infiltrative and tends to recur if not completely removed.
While major salivary gland tumors have their own staging system, minor salivary gland tumors are staged based on their anatomic subsite. The AJCC Cancer Staging Manual classifies the T stage of nasopharyngeal tumors based on the presence or absence of involvement of surrounding structures such as the parapharyngeal space, skull base, paranasal sinus, cranial nerves, hypoharynx, orbit, infratemporal fossa or masticator space . Like other cancers, N or nodal staging and M or metastasis staging are also important in the prognostication and treatment of these tumors. Our case presented as a T1N0M0 lesion given the absence of involvement of surrounding structures, lymph nodes or distance metastasis.
Multiple treatment modalities exist for the treatment of salivary gland tumors of the nasopharynx . Generally low-grade salivary gland tumors are less radiosensitive than their high-grade counterpart . The traditional therapeutic approach for patients with high-grade or unresectable (T4) disease is radiotherapy. A surgical approach is more appropriate for low-grade, low-stage adenocarcinomas. While the 5-year disease survival of patients with adenocarcinoma of the nasopharynx is approximately 65%, non-randomized studies demonstrate a survival benefit with the involvement of a surgical approach .
To our knowledge endoscopic resection of nasopharyngeal salivary gland tumors is not yet a common practice. Since the majority of patients with nasopharyngeal malignancies present with spread to cervical lymph nodes and/or the parapharyngeal space, less invasive techniques may not be considered. Primary endoscopic approaches to other nasopharyngeal neoplasms have been described with increasing frequency. Localized benign lesions such as juvenile nasal angiofibromas can be endoscopically resected, typically after angioembolization [11, 12]. Furthermore, while open surgical approaches have been the traditionally favored surgical modality for local control, there are now reports of endoscopic resection to address local recurrence of nasopharyngeal carcinoma [13, 14]. For other malignancies, such as localized chondroid cordoma of the nasoppharynx and skull base, some authors advocate strongly for the use of endoscopic resection as it spares the morbidity of open approaches [15, 16].
There is a paucity of literature that specifically pertains to the endoscopic resection of exocrine gland neoplasms of the nasopharynx, particularly as a primary therapy modality. Al-Sheibani et al. described their 4-handed endoscopic endonasal transpterygoid nasopharyngectomy in a retrospective study of twenty patients. Most patients in this study had advanced or recurrent disease. Among other tumors, 5 adenoid cystic and 2 adenocarcinomas were described with disease-related mortality rate of 20% and 50% respectively at the time of publication .
The low staging of our patient’s disease factored into our decision to pursue endoscopic resection. The absence of parapharyngeal extension or invasion of adjacent structures made the approach possible. Furthermore, the pedunculated nature of the lesion facilitated resection in that it made the tumor readily distinguishable from surrounding tissue. We were confident based on imaging and our exam findings that we would not only be able to resect the tumor but too achieve sufficient normal tissue margins with an endoscopic approach. Another factor favoring this approach was the indolent nature of this tumor, progressing minimally over a 3-year period. Our patient will require close surveillance and while we are confident that our resection was adequate, if the tumor recurs it should be detectable by physical examination.