1
Introduction
Sialolipoma is a rare and newly recognized distinct salivary gland neoplasm, which in a large series of over 2,000 cases had an overall incidence of 0.3% of salivary gland tumors in adults . Grossly it is characterized as a well-circumscribed, soft, yellow mass and histologically it contains both mature adipose tissue and entrapped normal salivary glandular components surrounded by a fibrous capsule.
Since the first description by Nagao et al there have been more than 30 cases of sialolipoma reported and reviewed; the majority of cases have involved the parotid gland, but submandibular and minor salivary gland tumors have also been described . While approximately 90% of the reported cases occurred in adults older than 18 years of age (mean age, 49.7), there have been three published cases in children less than five years old with only a single congenital parotid gland tumor reported .
We report a case of congenital sialolipoma of the parotid gland in a six week old male infant. To our knowledge, this is only the second congenital parotid gland sialolipoma reported.
2
Case report
A six week old male infant was referred to our department for evaluation of a left-sided facial mass. The infant was born at full term with no complications or other anomalies noted. There was no contributory family history.
By the infant’s one month well-child visit, the swelling had noticeably increased in size but he remained asymptomatic. His growth and development were otherwise normal. An ultrasound (US) identified prominent soft tissue in the region of the left parotid gland and subsequent magnetic resonance imaging (MRI) showed a relatively solid, 4.7 × 3 × 4.5 cm left parotid mass involving the superficial and deep lobes with irregular enhancement on T1-weighted imaging ( Fig. 1 ).
On presentation to our department at six weeks of age, physical exam was significant for a soft, non-tender, mobile, 5 × 5 cm left parotid mass without cervical lymphadenopathy. The parents reported that the mass had at least doubled in size since birth. No facial weakness was noted. US-guided core biopsies were obtained and revealed mature adipose tissue infiltrating normal-appearing salivary gland tissue which was consistent with sialolipoma, although malignancy and other lipomatous tumors could not be ruled out. Given the rapid enlargement of the mass and to confirm histologic diagnosis, the decision was made to surgically resect the parotid mass.
At eight weeks of age the infant underwent left total parotidectomy with facial nerve dissection and preservation. Facial nerve monitoring was used intra-operatively. After administration of general anesthesia and endotracheal intubation, a modified blair incision was utilized. In the usual fashion, sub-SMAS (superficial musculoaponeurotic system) flaps were raised to expose the parotid gland. The greater auricular nerve was identified and preserved. The main branch of the facial nerve was identified approximately between the posterior belly of the digastric muscle and the tragal pointer. The tumor was noted to involve both the superficial and deep lobes of the parotid gland ( Fig. 2 A ).
Interestingly, the main branch of the facial nerve was noted to be unusally long prior to identifying the pes anserinus . At this time, meticulous 360-degree dissection of the parotid and tumor from the facial nerve branches was performed ( Fig. 2 B). There were no areas where the tumor was adherent to the nerve; however, distal branches of the mid-face region that appeared to delve into the tumor were sacrificed.
Frozen sections were sent intra-operatively which indicated sialolipoma. The remaining tumor specimen was sent for permanent section. Estimated blood loss in the procedure was 20 ml. Post-operatively the patient experienced mild, transient upper and lower left sided facial weakness that resolved within 24 hours. A Jackson-Pratt drain that had been placed to bulb suction was removed after 48 hours. The patient was last seen in clinic three months post-operatively and was healing well without complications.
Grossly, the tumor specimen consisted of tan, yellow, lobulated salivary tissue weighing 29.4 grams and measured in aggregate 6.5 × 5.5 × 3.0 cm ( Fig. 2 C). Hematoxylin and eosin (H&E) staining for histological analysis was performed and final pathology revealed benign salivary gland tissue intermixed with mature adipose tissue which was surrounded by a fibrous capsule ( Fig. 2 D). The ratio of benign salivary gland tissue to mature adipose tissue was 1:1. The findings were most consistent with congenital sialolipoma.
2
Case report
A six week old male infant was referred to our department for evaluation of a left-sided facial mass. The infant was born at full term with no complications or other anomalies noted. There was no contributory family history.
By the infant’s one month well-child visit, the swelling had noticeably increased in size but he remained asymptomatic. His growth and development were otherwise normal. An ultrasound (US) identified prominent soft tissue in the region of the left parotid gland and subsequent magnetic resonance imaging (MRI) showed a relatively solid, 4.7 × 3 × 4.5 cm left parotid mass involving the superficial and deep lobes with irregular enhancement on T1-weighted imaging ( Fig. 1 ).
