A 65-year-old woman has noticed a slowly enlarging nodule on her face for the past 3 years. On physical examination, a 3-cm, nontender, mobile, discrete mass is palpable on the left side of the face, anterior to the ear and just superior to the mandible. The mass is completely excised, and histologic examination shows ductal epithelial cells in a myxoid stroma containing islands of chondroid like tissue and bone. This patient is most likely to have which of the following neoplasms?

**Core Concept**
The patient's presentation is suggestive of a benign salivary gland tumor, specifically one that arises from the ductal epithelium and exhibits a mixture of cartilaginous and bony tissue within a myxoid stroma.

**Why the Correct Answer is Right**
The histologic description is characteristic of a pleomorphic adenoma, also known as a benign mixed tumor. This neoplasm is the most common type of salivary gland tumor, accounting for approximately 60-70% of all cases. The presence of ductal epithelial cells, myxoid stroma, and islands of chondroid-like tissue and bone are all key features of pleomorphic adenoma. The tumor's slow growth and benign nature are reflected in its histology, which shows a mix of epithelial and mesenchymal elements.

**Why Each Wrong Option is Incorrect**
**Option A:** Warthin's tumor typically presents as a bilateral, painless mass in the parotid gland, and its histology shows oncocytic epithelial cells and a lymphoid stroma, which does not match the patient's presentation.
**Option B:** Mucoepidermoid carcinoma is a malignant salivary gland tumor that often presents with a mixture of mucous, epidermoid, and intermediate cells, but it typically lacks the myxoid stroma and chondroid-like tissue seen in this case.
**Option C:** Adenoid cystic carcinoma is a malignant salivary gland tumor that often presents with a cribriform or tubular growth pattern, and its histology shows mucous-filled cystic spaces, which does not match the patient's presentation.

**Clinical Pearl / High-Yield Fact**
Pleomorphic adenoma is the most common salivary gland tumor, and it often presents as a slowly enlarging, painless mass in the parotid gland or minor salivary glands. It is essential to distinguish pleomorphic adenoma from other salivary gland tumors, as it is generally benign and can be treated with surgical excision.

**Correct Answer:** C. Pleomorphic adenoma.

✓ Correct Answer: C. Pleomorphic adenoma