**Core Concept**
HPV-related cervical intraepithelial neoplasia (CIN) is a precancerous lesion caused by persistent human papillomavirus (HPV) infection, leading to abnormal cervical cell growth. The diagnosis of CIN relies on identifying characteristic histologic features in cervical biopsy specimens.

**Why the Correct Answer is Right**
The presence of koilocytic atypia, characterized by enlarged nuclei with prominent nucleoli, perinuclear halos, and cytoplasmic vacuolation, is a hallmark of HPV infection in cervical epithelial cells. This feature is often accompanied by a disordered arrangement of cells, increased mitotic activity, and the presence of binucleated or multinucleated cells. The koilocytic changes are a result of the HPV E6 and E7 proteins disrupting normal cell cycle regulation, leading to uncontrolled cell growth.

**Why Each Wrong Option is Incorrect**
**Option A:** The presence of metaplastic cells alone is not sufficient for diagnosing CIN, as metaplasia can occur in response to various stimuli, including hormonal changes or smoking.

**Option B:** Dysplasia, while a feature of CIN, is a non-specific term that can be used to describe abnormal cell growth in various tissues. It does not specifically indicate HPV infection or CIN.

**Option C:** The presence of a single mitotic figure does not necessarily indicate CIN, as mitotic activity can be seen in normal cervical epithelium.

**Clinical Pearl / High-Yield Fact**
Koilocytic atypia is often described as "orphan Annie eye" appearance due to the perinuclear halos surrounding the nucleus, making it a distinctive feature of HPV-related CIN.

**Correct Answer: C. Koilocytic atypia**