Abstract
Necrotizing sialometaplasia of the parotid gland is infrequent and can be mistaken as a malignant disease. Its etiology is thought to be an insufficient blood supply. Bilateral involvement of this disease in parotid glands has been rarely reported in the English literature. We report a case of necrotizing sialometaplasia diagnosed after superficial parotidectomy due to bilateral parotid masses in a 69-year old heavy smoking female.
1
Introduction
Necrotizing sialometaplasia is a chronic inflammatory disease of the salivary glands, mostly of oral minor salivary glands, with self-limited disease course. Despite its self-limiting process, it has a clinical importance as pathologic misdiagnoses are feasible . Etiology is thought to be an ischemic change on salivary glandular structure from secondary causes, although the precise pathogenesis has not been fully elucidated . When necrotizing sialometaplasia occurs on the parotid gland, an infrequent location for the development of this disease, there usually are preceding surgeries for the parotid mass, either benign or malignant . Only a small number of spontaneous development in parotid gland have been reported. Furthermore, spontaneous bilateral development has never been reported in literature to the best of our knowledge. We therefore report a case of necrotizing sialometaplasia of the bilateral parotid glands, confirmed after unilateral superficial parotidectomy, without any specific history of trauma or medical procedures.
2
Case report
A 69-year old female patient visited the outpatient clinic of otolaryngology head and neck surgery for evaluation of bilateral infraauricular masses found a few years earlier. She found these masses several years ago but neglected as there were no specific symptom. As they started to grow in size a month earlier, she received a treatment in a local clinic without any improvement. She was taking medications for hypertension and hypothyroidism, and had 25-pack years of smoking history. On physical examinations, a 3×2 cm sized non-tender but hard and fixed mass was palpated on left infraauricular area and a 1.5×1.5 cm sized similar natured mass was found on right infraauricular area. There was no other abnormal mass-like lesion on head and neck area. Neck CT revealed a 2×1.5 cm sized well enhancing mass with central necrosis on left parotid tail and another mass measuring 1.5×1 cm on right parotid tail ( Fig. 1 ). Fine needle aspiration biopsies were done in both sides with results of acute and chronic inflammatory cells. Because of failure to characterize the masses, excisional biopsy was planned and left superficial parotidectomy was performed preserving facial nerve. The patient showed no evidence of facial palsy or complications postoperatively.
On low power microscopic findings after Hematoxylin–Eosin staining, normal salivary gland tissue, necrotic area and lobular squamous metaplastic tissue were seen ( Fig. 2 A ). On the high power fields, necrosis was caseous, inflammatory cells were in the salivary ducts ( Fig. 2 B), and squamous metaplasia was seen in lobular pattern without any cellular atypia ( Fig. 2 C and D). Based on these findings, the mass was diagnosed as necrotizing sialometaplasia. As the mass on right parotid showed very similar nature compared to the left one, routine follow-up without surgery for the mass on the opposite side was planned. Follow up CT scan performed 8 months after the surgery showed no evidence of recurrence in the left side and no significant change of the size and character of the mass of the right side ( Fig. 3 ).
