Malignant Salivary Gland Tumors and Their Management

Mucoepideimoid Carcinoma

• Features: components of epidermoid, mucinous, and intermediate cells, high- and low-grade tumors

• most common salivary gland malignancy in children and adults (adenoid cystic carcinoma is the most common in the submandibular gland)

• most commonly found in the parotid

• commonly induced by radiation

• 30—70% overall regional metastatic potential

Types

Low-Grade (Well-Differentiated)

• Histopathology: more mucinous cystic elements, aggregates of mucoid cells with strands of epithelial cells, positive keratin staining

• approximately 70% 5-year survival

• Rx: superficial or total parotidectomy (for deep lobe involvement), radical neck dissection for clinically positive nodes

High-Grade (Poorly-Differentiated)

• Histopathology: less mucinous elements, more solid nests of cells, requires mucin staining to differentiate from squamous cell carcinoma, positive keratin staining

• Rx: superficial or total parotidectomy (for deep lobe involvement) with elective neck dissection (selective supraomohyoid neck dissection); radical neck dissection for clinically positive nodes; consider adjuvant radiation therapy for advanced tumors, regional disease, close or near surgical margins, or bone or neural involvement

Adenoid Cystic Carcinoma (Cylindroma)

• Features: high-grade tumor, aggressive, insidious growth (over several years), perineural spread (facial paralysis), local recurrence and distant metastasis (may present >5 years later)

• most common submandibular and minor gland malignancy

• Histopathology: low-grade have cribiform (nests of cells with round spaces, "Swiss cheese" appearance) or cylindromatous (tubular pattern) pattern, high-grade has more solid pattern (dense cellular pattern with few spaces)

• Prognosis: high-grade associated with poor prognosis (<20% 5-year survival), low-grade up to a 100% 5-year survival

• Rx: radical surgical resection (facial nerve resection if involved), consider adjunctive radiation therapy (or neutron beam); long-term follow-up required because of indolent course and possible distant metastasis, consider elective neck dissection versus postoperative radiation to the neck

Management

• Single-Modality Therapy: surgical excision of primary tumor for smaller tumors versus primary radiation for nonoperable candidates

• Multi-Modality Therapy: surgical excision of primary tumor with adjuvant radiation for advanced tumors, regional metastasis, close or near surgical margins, or bone or neural involvement

• Neck: radical neck dissection for clinical nodes only

Malignant Mixed

• Features: high-grade tumor, aggressive, explosive growth rate, poor prognosis (<50% 5-year survival)

• Rx: surgical excision with postoperative radiation therapy, may consider elective neck dissection (supraomohyoid)

Types

• Carcinoma Ex-Pleomorphic Adenoma: 2—3% malignant transformation from pleomorphic adenomas, carcinoma components only (arises from epithelial component)

• Metastasizing Mixed Tumor: distinct from carcinoma ex-pleomorphic, remains histologically benign

• Carcinosarcoma: contains components of both carcinomas and sarcomas

• Noninvasive Carcinoma: carcinoma in situ within a pleomorphic adenoma

Acinic Cell Carcinoma

• Features: low-grade, better prognosis (63—87% 10-year survival)

• second most common salivary gland cancer in pediatrics

• most commonly found in the parotid (serous acinar cells)

• Histopathology: serous acinar cells or clear cytoplasm cells, several configurations (microcystic, papillary, solid, follicular), lymphoid infiltrate

• Rx: surgical excision with wide margins, neck dissection for positive nodes only, adjuvant radiation therapy may be considered for advanced disease

Other Salivary Gland Malignancy Types

• Squamous Cell Carcinoma: high-grade, aggressive, often not the primary (must evaluate for primary)

• Lymphomas: rare as a primary site although may arise from intraglandular lymphoid tissue (from embryonic development), associated with Sjogren's Syndrome (see Head and Neck Cancer: Other Head and Neck Malignancy)

• Adenocarcinoma: high-grade, aggressive, originates from terminal tubules or intercalated ducts

• Malignant Oncocytoma: similar to the benign form with distant metastasis and local invasion

• Epithelial-Myoepithelial Carcinoma (Clear Cell): low-grade

• Salivary Duct Carcinoma: high-grade, similar to ductal carcinoma of the breast

• Undifferentiated Carcinoma: highly aggressive, worst prognosis, predominantly "small cell"

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