A 58-year-old woman from Mumbai presents with a 3-month history of progressive pain and swelling in the left submandibular region. On examination, the mass is hard, fixed to surrounding tissues, and the overlying skin appears erythematous. She reports difficulty in swallowing and a recent episode of facial nerve weakness on the left side. FNAC reveals mucous cells, intermediate cells, and epidermoid cells with marked nuclear atypia and increased mitotic figures. What is the most likely diagnosis?

Explanation

## Diagnosis: Mucoepidermoid Carcinoma **Key Point:** Mucoepidermoid carcinoma (MEC) is the most common **malignant** salivary gland tumor in both children and adults, accounting for 20–30% of all salivary malignancies. ### Clinical Features of Mucoepidermoid Carcinoma | Feature | Presentation | | --- | --- | | **Age** | Can occur at any age; peak 40–60 years | | **Location** | Parotid (most common), submandibular, minor salivary glands | | **Growth** | Rapid (weeks to months) | | **Pain** | Present (indicates invasion) | | **Fixation** | Fixed to surrounding tissues | | **Skin changes** | Erythema, ulceration possible | | **Nerve involvement** | Facial nerve palsy (poor prognostic sign) | ### FNAC Findings (Diagnostic) - **Three cell types:** Mucous, intermediate, and epidermoid cells - **Background:** Mucoid material - **Atypia:** Marked nuclear atypia and increased mitotic figures - **This combination is pathognomonic for MEC** **High-Yield:** The presence of **three distinct cell populations (mucous + intermediate + epidermoid) with atypia** on FNAC is diagnostic for mucoepidermoid carcinoma. ### Grading (Histopathology) 1. **Low-grade:** Better prognosis, slow growth, minimal atypia 2. **Intermediate-grade:** Moderate atypia and growth rate 3. **High-grade:** Poor prognosis, rapid growth, marked atypia, necrosis ### Management Algorithm ```mermaid flowchart TD A[Mucoepidermoid Carcinoma Diagnosed]:::outcome --> B{Grade & Stage?}:::decision B -->|Low-grade, early| C[Superficial/total parotidectomy<br/>with FN preservation]:::action B -->|High-grade or advanced| D[Wide surgical excision<br/>+ neck dissection]:::action D --> E[Consider adjuvant radiotherapy<br/>or chemotherapy]:::action C --> F[Follow-up surveillance]:::action E --> F ``` **Clinical Pearl:** Facial nerve involvement (as in this case) indicates aggressive behavior and is an independent poor prognostic factor. Nerve preservation should be attempted only if tumor can be separated cleanly. **Warning:** Do not confuse with pleomorphic adenoma—MEC shows **atypia and three distinct cell types**, whereas pleomorphic adenoma is benign with myxoid/chondroid stroma.