Pleomorphic Adenoma Benign Mixed Tumor

Introduction

• benign heterogeneous tumor composed of variable epithelial and myoepithelial components

• most common tumor of each gland (may also be found in the respiratory tract and nasal cavity)

• slightly more common in women

• SSx: slow growing (over years), unilateral, painless, firm mass (usually toward the tail of the parotid); rarely progresses to dysphagia (pharyngeal extension), dyspnea, or hoarseness (laryngeal involvement), or facial nerve palsies; deep lobe (10%) involvement may present with intra-oral swelling

• Recurrent SSx: multilobular nodules, not discrete; may arise in scar, subcutaneous tissue, deep lobe, or facial nerve sheath

• Complications: rare malignant transformation (Carcinoma Ex-Pleomorphic Adenoma and Sarcoma) or "benign" metastasizing (see pp. 78-79)

• Dx: biopsy specimen (parotidectomy), FNA

• Rx: surgical resection (superficial or total parotidectomy, see below) with wide margin for pseudopod extensions to prevent recurrence (>90% 10-year cure, approximately 30% recurrence rate for enucleation alone), radioresistant

Histopathology

• Cellular Components

1. myoepithelial component: spindle shaped with hyperchromatic nuclei, may be more than one cell layer thick

2. epithelial components: varied growth patterns (trabecular, solid, cystic, papillary)

3. stromal components: product of myoepithelial cells: myxoid, chondroid, fibroid, or osteoid components

• fibrous pseudocapsule (except minor glands)

• micro-pseudopod extensions

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