True about Brenner tumor:a) Usually bilateralb) Resembles fibromac) Accounts for 20% of all ovarian tumorsd) Common in postmenopausal age group

**Core Concept**
Brenner tumors are a type of sex cord-stromal tumor of the ovary, characterized by their distinctive histological features and clinical behavior. They are typically benign and arise from the ovarian stroma, often mimicking a fibrous or cartilaginous structure.

**Why the Correct Answer is Right**
The correct answer is **d) Common in postmenopausal age group**. Brenner tumors are most commonly diagnosed in postmenopausal women, with a peak incidence between the ages of 55 and 65. This is in contrast to other types of ovarian tumors, which may be more common in younger women. The exact reason for this age-related incidence is not fully understood, but it is thought to be related to the gradual accumulation of genetic mutations in the ovarian stroma over time.

**Why Each Wrong Option is Incorrect**
**Option A:** Brenner tumors are typically unilateral, rather than bilateral, which rules out this option.
**Option B:** While Brenner tumors may have a fibrous appearance under the microscope, they do not resemble fibromas, which are a different type of ovarian tumor altogether.
**Option C:** Brenner tumors account for only a small percentage of all ovarian tumors, typically less than 5%, which makes this option incorrect.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Brenner tumors are often asymptomatic and may be discovered incidentally during imaging studies or surgery for other reasons. They are typically characterized by a well-circumscribed, solid mass with a smooth surface.

**Correct Answer: D. Common in postmenopausal age group.**