## Diagnosis: Adenoid Cystic Carcinoma **Key Point:** Adenoid cystic carcinoma (AdCC) is the second most common malignant salivary gland tumor and is classically characterized on FNAC/histology by a **cribriform pattern** with epithelial cells arranged around cylindromatous (mucoid) spaces, accompanied by **myoepithelial cells** — this is the pathognomonic finding described in this case. **High-Yield:** The cribriform ("Swiss cheese") pattern on FNAC with both epithelial and myoepithelial cells is the hallmark of adenoid cystic carcinoma, NOT pleomorphic adenoma. Pleomorphic adenoma shows a chondromyxoid stroma with epithelial and myoepithelial cells but does NOT characteristically produce a cribriform arrangement. ### Clinical Features of Adenoid Cystic Carcinoma | Feature | Adenoid Cystic Carcinoma | |---------|--------------------------| | Growth rate | Slow but relentless | | Pain | Can be present (perineural invasion) | | Facial nerve involvement | Common (perineural spread) | | Mobility | May be fixed in advanced cases | | Age of presentation | 40–60 years | | Most common site | Minor salivary glands > parotid | | FNAC/Histology | Cribriform pattern, epithelial + myoepithelial cells | | Malignant potential | Inherently malignant; late distant metastases | **Clinical Pearl:** Adenoid cystic carcinoma is notorious for **perineural invasion** (leading to pain and facial nerve palsy in advanced cases) and **late distant metastases** (especially to the lungs), even after apparent local control. Early lesions, as in this vignette, may still present as a painless mobile mass with intact facial nerve — making FNAC findings critical for diagnosis. (Reference: Cummings Otolaryngology, 7th ed.; Robbins & Cotran Pathologic Basis of Disease, 10th ed.) ### Why Adenoid Cystic Carcinoma Fits This Case 1. Slow-growing, painless parotid mass in a middle-aged man (early presentation) 2. Intact facial nerve (early stage — perineural invasion is a later feature) 3. **FNAC shows cribriform pattern with epithelial and myoepithelial cells** — pathognomonic for AdCC 4. No mucosal involvement (consistent with parotid primary) ### Why the Other Options Are Incorrect - **Mucoepidermoid carcinoma (A):** FNAC shows mucous cells, epidermoid cells, and intermediate cells — NOT a cribriform pattern. - **Acinic cell carcinoma (C):** FNAC shows cells with abundant granular cytoplasm resembling serous acinar cells — NOT a cribriform pattern. - **Pleomorphic adenoma (D):** FNAC shows epithelial and myoepithelial cells in a **chondromyxoid stromal background** — the cribriform arrangement is NOT characteristic; it is the hallmark of AdCC. **Mnemonic:** AdCC = **A**denoid cystic = **C**ribriform + **C**ylindroma + perineural invasion. 
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