Salivary Gland Tumors

• Lecture focuses on salivary gland tumors.

Types of Salivary Gland Tumors

• Primary tumors can be benign or malignant and arise from epithelial or connective tissue.
• Benign epithelial tumors include pleomorphic adenoma, adenolymphoma, oncocytoma, and monomorphic adenoma.
• Malignant epithelial tumors include carcinoma.
• Benign connective tissue tumors include haemangioma, lymphangioma, lipoma, and neurofibroma.
• Malignant connective tissue tumors include sarcoma and lymphomas.
• There are also secondary tumors.

Incidence

• 80% of salivary neoplasms arise in the parotid gland.
• 80% of these parotid tumors are benign.
• Pleomorphic adenomas are the most common type of benign tumors.
• Malignancy rates vary among salivary glands, with sublingual and minor glands having the highest rate (70%) compared to parotid (20%) and submandibular (50%).
• Parotid tumors account for 80% of tumor incidence, followed by submandibular (15%) and sublingual & minor glands (5%).

Pleomorphic Adenoma

• The most common parotid tumor, representing 80% of benign parotid tumors.
• Characterized as common in the parotid gland.
• Described as small and firm with an incompletely encapsulated and lobulated surface.
• Cut surface is greyish-white and may present cystic formation.
• Cells consist of epithelial and myoepithelial cells that are spindle or stellate shaped.
• Cells arranged in acini, clusters, or sheets.
• Stroma appears blue resembling cartilage.
• Presence of microscopic extensions beyond the tumor capsule contributes to the high recurrence rate after simple enucleation.
• Patients typically show slowly growing, painless swelling.
• Swelling may be bilateral and has specific criteria such as being single, hemispherical, freely mobile, with a smooth & lobulated surface, firm consistency, and well-defined edge.
• Facial nerve is free, and the masseter muscle is not attached.

Investigations and Treatment of Pleomorphic Adenoma

• Investigations include ultrasound, CT or MRI for larger tumors, and FNAC.
• Treatment options: extracapsular dissection (ECD), superficial parotidectomy, total conservative parotidectomy, and partial (limited) superficial parotidectomy for small tumors of the superficial lobe.

Warthin's Tumour

• The second most common parotid tumor, accounting for 10% of benign parotid tumors.
• Smoking and radiation exposure are potential etiological factors, as well as autoimmune disease.
• Located in the lower part of the parotid gland and affects other salivary glands.
• Occurs bilaterally in 10% of cases,.
• Small, completely encapsulated cystic mass, exhibiting white areas on the cut surface due to lymphoid tissue around cystic structures.
• Lymphocytic infiltrate and cystic epithelial proliferation.
• Cells are derived from parotid duct cells due to metaplasia, arranged in two layers into cystic spaces containing mucoid material that forms papillary projections.
• Stroma consists of lymphoid tissues originating from lymphoid aggregations in normal parotid glands.
• More common in males over 50 years.
• Presents as slow growing, painless swelling.
• Palpable mass has a soft/cystic consistency.
• Tumors benign and don't recur locally, enucleation is sufficient.
• Enucleation reduces the risk of temporary facial neuropraxia from 43% with superficial parotidectomy to 8% with controlled enucleation.
• Superficial parotidectomy required for multiple lesions and to identify the facial nerve.
• Total conservative parotidectomy is performed for lesions in the deep portion of the gland.

Malignant Tumors Epidemiology

• More common in males, except for acinic cell carcinoma, which is more common in females.
• Typically occurs in individuals over 50 years old, excluding acinic cell and mucoepidermoid carcinomas, which can occur in children.

Malignant Tumours Site

• 25% of parotid tumors.
• 50% of submandibular tumors.
• 75% of sublingual tumors.
• 100% of minor salivary gland tumors are malignant.

Malignant Tumours Predisposing Factors

• Radiation (ionizing radiation and iodine-131 therapy).
• Occupational exposure (rubber manufacturing, nickel, asbestos, chronic wood dust inhalation).
• Infection (human papilloma virus (HPV)).
• Eskimo heritage.

Precancerous Lesions

• Pleomorphic adenoma.

Malignant Tumours Gross Pathology

• Large
• Hard mass
• Nodular or irregular surface
• Cut section shows areas of hemorrhage & necrosis and cyst formation.

Specific Carcinomas Histopathology

• Mucoepidermoid carcinoma contains both squamous and mucous secreting epithelium forming cysts, and most common in the parotid.
• Adenoid cystic carcinoma consist of epithelial cells arranged in columns around central cavities of mucous giving “Swiss -cheese pattern", most common in the submandibular, and displays perineural spread.
• Acinic cell carcinoma consist of epithelial cells that resemble serous acini and more common in females >40 years old & in children.
• Adenocarcinoma are malignancies that cannot otherwise be easily classified.
• Carcinoma ex-pleomorphic adenoma originates from a pre-existing pleomorphic adenoma.

Symptoms of Malignant Tumours.

• Rapidly growing (adenoid cystic carcinoma has slow rate of growth).
• Painful swelling.

Single, slightly tender swelling

• Site: Usually in the parotid region.
• Size: Variable (rapidly growing).
• Shape: Irregular.
• Surface: Nodular or irregular.
• Skin over: Attached to the tumour (not freely mobile).
• Surrounding structures: Facial nerve or masseter muscle may be infiltrated.
• Consistency: Hard (soft in acinic cell tumour).
• Edge: Ill-defined edge.
• Lymph nodes: enlarged hard, painless, early mobile, and later fixed.

Investigations

• Neck US (locally advanced cancers to detect perineural spread).
• CT scan or MRI (lesions in the deep lobe and extracapsular extensions).
• FNAC (sensitive, specific for parotid tumours).
• CNB (may be used in hard tumours).
• Chest X-ray (in locally advanced cases for metastatic work up).

Treatment

• Superficial parotidectomy for Low-grade tumors and selected high-grade tumors peripherally in the superficial lobe
• Total parotidectomy for high-grade tumors and deep lobe tumors.
• Radical parotidectomy for tumours infiltrating the facial nerve, offers facial nerve reconstruction with good results using cervical plexus branches as interposition nerve grafts and microscopic epineural repair.
• Extended parotidectomy is required for locally advanced tumors, including resection of masseter, mandible part, and infiltrated skin, and soft tissue reconstruction.

Lymph Node Management

• Elective neck dissection (levels II and III) indicated for high-grade tumors (except adenoid cystic carcinoma) and locally advanced tumors (T3 & T4).
• Modified radical block neck dissection for node-positive cases.
• Post-operative radiotherapy indicated in cases with close or positive margins, intermediate or high grade, adenoid cystic carcinoma, neural/perineural invasion, lymphatic/vascular invasion, residual tumour, or recurrent tumour.
• Inoperable cases (including T4b) require definitive radiotherapy or concurrent chemoradiotherapy.
• Low grade mucoepidermoid and Acinic cell tumour have a favourable prognosis.
• Squamous cell carcinoma and Adenoid cystic carcinoma have an unfavourable prognosis.