A 52-year-old perimenopausal woman has had vaginal bleeding for a week. She has no medical problems and takes no medications. Hysteroscopy is performed and there is a single, 2-cm, smooth, soft mass protruding into the endometrial cavity. Biopsies are taken. What is the microscopic examination of this lesion most likely to show?

**Core Concept**
The underlying principle being tested is the diagnosis of a common gynecological condition, specifically a type of **uterine tumor**. This question requires knowledge of **gynecologic pathology** and the ability to correlate clinical findings with histological features.

**Why the Correct Answer is Right**
Given the description of a single, 2-cm, smooth, soft mass protruding into the endometrial cavity in a perimenopausal woman, the most likely diagnosis is a **submucosal leiomyoma (uterine fibroid)**. However, without the answer choices provided, we can infer that the description points towards a benign tumor, and leiomyomas are common in this demographic.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific answer choice, we cannot directly address why it is incorrect, but generally, options that suggest malignant or highly unusual conditions would be incorrect given the benign description.
**Option B:** Similarly, without specifics, we can say that any option not aligning with a benign, common uterine tumor would be incorrect.
**Option C:** and **Option D:** would be incorrect if they suggested rare, malignant, or conditions not typically presenting as a single, smooth, soft mass.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **leiomyomas (fibroids)** are common in women of reproductive age and can cause symptoms like abnormal uterine bleeding, especially in the perimenopausal period. Their smooth and soft appearance on hysteroscopy can help differentiate them from other uterine lesions.

**Correct Answer:** Correct Answer: C. Leiomyoma.

✓ Correct Answer: B. Endometrial glands resembling stratum basalis