Answer:
Parotid masses in children are more likely to be of vascular origin, however, compared with adults, a solid tumor in a child is twice as likely to be malignant. Ultrasound and/or MRI is often used to confirm whether a lesion is vascular or solid.
Hemangiomas account for 50% of parotid neoplasms in the pediatric population. Girls are more commonly affected. These masses usually present at birth or within the first few months of life. On exam, the mass is soft and compressible. It may enlarge and tense up with crying and straining. Facial nerve function is not affected. Aside, from MRI and ultrasound, labeled RBC scans can also confirm the diagnosis of hemangioma. Because the majority of lesions involute spontaneously, treatment is usually conservative, although parents may demand excision for cosmetic reasons. Early excision may be indicated in circumstances where there is overly rapid growth of the mass, functional impairment (i.e. eye or oral function), infection, hemorrhage, or ulceration.
Lymphangioma or cystic hygroma is second most common. This developmental abnormality of the lymphatic system often presents as a diffuse mass involving not only the parotid but also surrounding structures. The mass is soft and frequently can be transilluminated. Like hemangiomas, most lymphangiomas are present at birth or soon thereafter. Unlike hemangiomas, lymphangiomas do not replace the normal parenchymal tissue. Islands of normal salivary tissue are often seen next to thin-walled lymph-containing vessels. They will usually slowly enlarge with time though rapid growth may occur with trauma, URI, or hemorrhage into the cyst. Acute enlargement may be associated with upper airway compression or facial weakness secondary to facial nerve compression. Definitive diagnosis can be made by either CT or MRI. Ultrasound may help determine if a lesion is cystic but the former modalities are better for anatomic delineation. Surgical excision is the treatment of choice and should be performed within the first few years of life though the exact timing is controversial. Recurrence rates of 10-15% have been reported within the first year after excision.
Pleomorphic adenoma is the most common solid tumor mass seen in children. It often presents as a small, 1-cm, firm discrete nodule which is slow-growing and mobile on exam. It is usually seen in an older age group compared to vascular tumors (often in adolescence) and more often in girls. CT and MRI are useful for anatomic delineation. Superficial parotidectomy with facial nerve preservation is usually the treatment of choice. Though recurrences are now rare, because of their slow-growing nature, long-term follow-up is recommended.
Primary malignant tumors of the parotid are rare in children, but together they make up over 50% of solid firm lesions detected in the gland, so any solid firm parotid mass in a child should be taken very seriously. They tend to occur later in childhood or in adolescence. Rapid growth or fixation or any facial nerve involvement is highly suggestive of malignancy as is local pain, especially if it is out of proportion to any apparent inflammatory reaction. CT and MRI should be done for anatomic delineation and surgical planning. Because excisional biopsy is not recommended for fear of seeding, parents should be prepared preoperatively for the potential need for wide resection. Among malignant parotid tumors, mucoepidermoid carcinomas are by far the most common (51.7%). Acinic cell carcinomas (16.8%) are a distant second, followed by undifferentiated carcinomas (8.7%), adenocarcinomas (8.1%), and adenoid cystic carcinomas (7.6%).
Mucoepidermoid tumors are derived from the intralobular salivary ducts. It can be classified as low or high grade. For low-grade lesions superficial parotidectomy is recommended, while total parotidectomy is usually performed for high-grade lesions. Lymph node metastasis occurs in about 20% and despite complete surgical excision, local recurrence occurs about 30% of the time. Radical neck dissection is recommended in children only for clinically evident cervical lymph nodes with poorly differentiated and high-grade lesions. However, with aggressive surgical treatment and adjunctive radiation therapy, overall 5-year survival rates of 90% have been reported. The remaining types of malignant tumors are associated with poorer prognoses.