**Core Concept**
Egg cell calcification is a rare pathological condition characterized by the deposition of calcium salts within the ovary, leading to the formation of calcified ovarian follicles. This phenomenon is often associated with aging, but it can also be caused by other factors such as tumors or inflammation.

**Why the Correct Answer is Right**
Egg cell calcification is most commonly seen in **Granulosa cell tumors**, which are a type of sex cord-stromal tumor that arises from the granulosa cells of the ovary. These tumors can cause the calcification of ovarian follicles, leading to the formation of a characteristic "eggshell" calcification pattern on radiographic imaging. This is due to the abnormal proliferation of granulosa cells, which can lead to an overproduction of estrogen and the subsequent calcification of the ovarian stroma.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because calcification of ovarian cysts is not a characteristic feature of this condition. While ovarian cysts can calcify, this is not the same as egg cell calcification.

**Option B:** This option is incorrect because egg cell calcification is not a feature of benign ovarian cysts. While benign ovarian cysts can cause a range of symptoms, calcification of the ovarian follicles is not a characteristic feature.

**Option C:** This option is incorrect because egg cell calcification is not a feature of endometriosis. While endometriosis can cause a range of symptoms, including pelvic pain and infertility, calcification of the ovarian follicles is not a characteristic feature.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that egg cell calcification can be a feature of various conditions, including tumors and inflammation. Therefore, a diagnosis of egg cell calcification should be made in conjunction with a thorough clinical evaluation and radiographic imaging.

**Correct Answer:** A. Granulosa cell tumors.