## Diagnosis: Adenoid Cystic Carcinoma **Key Point:** Adenoid cystic carcinoma (ACC) is a malignant salivary gland tumor classically characterized by a **cribriform (Swiss-cheese) pattern** on histology, with epithelial cells and myoepithelial cells arranged around pseudocystic spaces. This is its pathognomonic histological feature. ### Clinical Features - **Presentation:** Painless (or mildly painful), slow-growing mass — can mimic a benign tumor early on - **Consistency:** Firm, may be mobile in early stages - **Facial nerve:** Often intact early; perineural invasion is a hallmark but may not cause clinical palsy at presentation - **Intraoral:** No mucosal involvement in parotid primaries - **Perineural invasion:** The most characteristic feature of ACC — responsible for late recurrences and skip lesions along nerve sheaths ### Histopathology (FNAC / Biopsy) Three classic patterns (in decreasing order of frequency): 1. **Cribriform pattern** — most common; epithelial and myoepithelial cells arranged in a sieve-like (Swiss-cheese) pattern around cylindromatous pseudocysts filled with basement membrane material 2. **Tubular pattern** — better prognosis 3. **Solid/basaloid pattern** — worst prognosis > The FNAC description in this vignette — *"epithelial cells arranged in a cribriform pattern with myoepithelial cells"* — is **pathognomonic for adenoid cystic carcinoma**, not pleomorphic adenoma. ### Why Not the Other Options? - **Pleomorphic adenoma (B):** Benign; histology shows a *mixed* pattern with epithelial ducts, myoepithelial cells, AND a characteristic **stromal component** (myxoid, chondroid, hyalinized). The cribriform pattern is NOT its defining feature. - **Acinic cell carcinoma (A):** Shows acinar differentiation with basophilic zymogen granules; no cribriform pattern. - **Mucoepidermoid carcinoma (C):** Shows mucous cells, epidermoid cells, and intermediate cells; no cribriform pattern. ### Management - **Imaging:** MRI (best for perineural spread along cranial nerves) - **Treatment:** Wide surgical excision + postoperative radiotherapy (ACC is relatively radioresistant but adjuvant RT improves local control) - **Prognosis:** Deceptively slow course with late distant metastases (lung most common); 10-year survival ~50% **High-Yield:** ACC is the most common malignant tumor of the **submandibular and minor salivary glands**. In the parotid, it is less common than mucoepidermoid carcinoma but is the classic "cribriform pattern" tumor tested in exams. **Clinical Pearl:** Perineural invasion by ACC can cause pain, paresthesia, or facial nerve palsy — but early lesions may be clinically silent, as in this vignette. Always suspect ACC when FNAC shows a cribriform pattern with myoepithelial cells. *(Reference: Scott-Brown's Otorhinolaryngology; Robbins & Cotran Pathologic Basis of Disease, 10th ed.)* 
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