Salivary Neoplasms - الأهلية

• Salivary gland tumors are discussed in this lecture.

Types of Salivary Gland Tumors

• Primary tumors can be benign or malignant.
• Benign epithelial tumors include pleomorphic adenoma, adenolymphoma, oncocytoma, and monomorphic adenoma.
• Other benign tumors include haemangioma, lymphangioma, lipoma, and neurofibroma.
• Malignant epithelial tumors include carcinoma.
• Connective tissue malignant tumors include sarcoma and lymphomas.
• Secondary tumors can also occur.

Incidence of Salivary Gland Tumors

• Approximately 80% of salivary neoplasms arise in the parotid gland.
• Of these, 80% are benign.
• Most benign tumors are pleomorphic adenomas.
• The malignancy rate varies among salivary glands, with sublingual and minor glands having a higher rate than the parotid.
• Incidence rate in parotid gland = 80%
• Incidence rate in submandibular gland = 15%
• Incidence rate in sublingual and minor glands = 5%
• Malignancy rate in parotid gland = 20%
• Malignancy rate in submandibular gland = 50%
• Malignancy rate in sublingual & minor gland = 70%

Pleomorphic Adenoma (Benign)

• The most common parotid tumor, accounting for 80% of benign parotid tumors.
• Usually found in the parotid gland.
• Characterized by small, firm, incompletely encapsulated masses with a lobulated surface
• Cut surface is greyish-white with occasional cystic formations.
• Histopathology shows pleomorphism with epithelial and myoepithelial cells.
• Cells have spindle or stellate shapes and are arranged in acini, clusters, or sheets.
• The stroma appears blue and resembles cartilage.
• Microscopic extensions exist beyond the tumor's capsule, contributing to a high recurrence rate following simple enucleation.

Clinical Presentation of Pleomorphic Adenoma

• Slow growth and painless swelling.
• Swelling may be bilateral.
• Single in number
• Hemispherical in shape, with a smooth, lobulated surface.
• Skin over the swelling is freely mobile.
• Well-defined edge.
• Facial nerve and masseter muscle are not attached.
• Firm consistency, but never hard.

Investigations and Treatment for Pleomorphic Adenoma

• Ultrasound, CT, or MRI may be needed, especially for larger tumors.
• Fine-needle aspiration cytology (FNAC) is also used.
• Treatment options include extracapsular dissection (ECD), superficial parotidectomy, total conservative parotidectomy, and partial (limited) superficial parotidectomy.
• The last is designed for small tumors of the superficial lobe.

Warthin's Tumor

• The second most common parotid tumor, representing 10% of benign parotid tumors.
• Risk factors include smoking, radiation exposure, and autoimmune diseases.
• Located in the lower part of the parotid gland, without affecting other salivary glands, and is bilateral in 10% of cases.
• Small, cystic, completely encapsulated mass with white areas on the cut section due to lymphoid tissue.
• Consists of Lymphocytic infiltrate and Cystic epithelial proliferation
• Derived from parotid duct cells due to metaplasia.
• Has 2 layers arranged into cystic spaces containing mucoid material lining the cysts, with the formation of papillary projections.
• Stroma consists of lymphoid tissues originating from lymphoid aggregations in normal parotid glands that support cystic spaces

Clinical Presentation and Treatment of Warthin's Tumor

• More common in males than females and in patients over 50 years old.
• Presents as a slowly growing, painless, cystic swelling similar to pleomorphic adenoma but with a cystic consistency (never hard).
• Benign and do not recur locally, this allows for treatments that reduce temporary facial neuropraxia.
• Enucleation reduces temporary facial neuropraxia from 43% for superficial parotidectomy to 8% for controlled enucleation.
• Superficial parotidectomy is required for multiple lesions where identification of the facial nerve is required.
• Total conservative parotidectomy is used 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 occur in individuals over 50 years, except acinic cell carcinoma and mucoepidermoid carcinoma which can also occur in children.

Predisposing Factors for Malignant Salivary Gland Tumors

• Ionizing radiation and iodine-131 therapy
• Rubber manufacturing and nickel exposure
• Asbestos exposure and chronic wood dust inhalation
• Human papilloma virus (HPV) infection
• Eskimo heritage

Precancerous Lesions

• Pleomorphic adenoma

Pathology of Malignant Salivary Gland Tumors

• 25% occur in the parotid tumors, 50% occur in the submandibular tumors, 75% in the sublingual tumors
• 100% of minor salivary gland tumors are malignant.
• Large, hard mass with a nodular or irregular surface.
• Cut section reveals areas of hemorrhage, necrosis, and cyst formation.

Histopathology of Specific Malignant Tumors

• Mucoepidermoid carcinoma, most common in the parotid, contains both squamous and mucous secreting epithelium forming cysts.
• Adenoid cystic carcinoma, most common in the submandibular gland, consists of epithelial cells arranged in columns around central cavities giving a "Swiss-cheese pattern" and is characterized by perineural spread.
• Acinic cell carcinoma is more common in females over 40 and children consisting of epithelial cells resembling serous acini.
• Adenocarcinomas are for malignancies that cannot be easily classified.
• Carcinoma ex-pleomorphic adenoma is a malignant epithelial element arising from a pre-existing pleomorphic adenoma.

Clinical Presentation

• Rapidly growing with rapid growth rate in adenoid cystic carcinoma
• Painful Swelling
• Single, slightly tender swelling which has the following criteria:
• Site usually in the parotid region
• Size variable which grows rapidly
• Shape irregular
• Surface nodular or irregular
• Skin over is attached to the tumor and not freely mobile
• Surrounding structures, such as the facial nerve or masseter muscle, may be infiltrated.
• Hard consistency, with soft consistency specifically in an acinic cell tumor
• Ill-defined edge.
• Enlarged hard, painless, early mobile and later fixed lymph nodes

Investigations for Malignant Tumors

• Neck ultrasound to detect perineural spread in locally advanced cancers.
• CT scan or MRI for lesions situated within the deep lobe and extracapsular extensions.
• FNAC (sensitive at >95% and specific) and core needle biopsy (CNB) for diagnosis
• Chest X-ray for metastatic workup

Treatment: Operable Radical Procedures

• Superficial parotidectomy for low-grade tumors and selected high-grade tumors of the superficial lobe located peripherally, particularly in the inferior pole.
• Total parotidectomy for high-grade and deep lobe tumors.
• Radical parotidectomy for tumors infiltrating the facial nerve, with possible primary reconstruction of the facial nerve using the great auricular nerve or interposition nerve grafts.
• Extended parotidectomy for locally advanced tumors requiring resection of adjacent tissues, such as the masseter, mandible, and overlying skin if infiltrated.

Lymph Node Management and Other Treatments

• Elective neck dissection (levels II and III) 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 if there are close or positive margins, intermediate or high grade tumors, adenoid cystic carcinoma, neural/perineural invasion, lymphatic/vascular invasion, residual tumors, or recurrent tumors.
• Definitive radiotherapy or concurrent chemoradiotherapy for inoperable cases (including T4b disease).

Prognosis

• Favorable prognosis: low-grade mucoepidermoid, acinic cell tumor
• Unfavorable prognosis: squamous cell carcinoma, adenoid cystic carcinoma