**Question:** In which one of the following salivary gland tumors, the tumor is composed of "intermediate cells" histologically?

A. Warthin's tumor (papillary cystadenoma lymphomatosum)
B. Pleomorphic adenoma
C. Mucoepidermoid carcinoma
D. Acinic cell carcinoma

**Correct Answer: D. Acinic cell carcinoma**

**Core Concept:**
Salivary gland tumors are a diverse group of benign and malignant neoplasms. Histologically, they are characterized by the type of cells they consist of. In this question, we are looking for a tumor that has intermediate cells as a component.

**Why the Correct Answer is Right:**
Acinic cell carcinoma is a malignant tumor originating from the exocrine cells of the salivary glands, specifically the acinar cells. This type of tumor consists of intermediate cells, which are a combination of ductal, basal, and acinar cells. These cells are responsible for producing and secreting the main components of saliva, such as enzymes (amylase, trypsin, and lipase).

**Why Each Wrong Option is Incorrect:**

A. Warthin's tumor (papillary cystadenoma lymphomatosum) is a benign tumor composed of lymphoid tissue and epithelial cells. It does not contain intermediate cells.

B. Pleomorphic adenoma is a benign tumor composed of both myoepithelial cells and epithelial cells. It does not contain intermediate cells.

C. Mucoepidermoid carcinoma is a malignant tumor consisting of three cell types: mucous, intermediate, and squamous cells. Intermediate cells are not a defining characteristic of this tumor.

**Clinical Pearl:**
Understanding the histopathology of salivary gland tumors is essential for accurate diagnosis and treatment planning. Acinic cell carcinoma is a rare but potentially aggressive tumor, and proper identification of its histopathological features helps guide treatment decisions and prognosis.