**Core Concept**
Fordyce spots are small, yellow or white, intradermal or perifollicular sebaceous glands that are ectopically located on the skin. They are a benign condition and are usually found on the lips, genitalia, or inside the cheeks.

**Why the Correct Answer is Right**
Fordyce spots occur due to the abnormal development of sebaceous glands during embryogenesis. Normally, these glands are located in the hair follicles, but in the case of Fordyce spots, they are found on the surface of the skin. This is thought to be due to the failure of these glands to migrate into the hair follicles during fetal development. As a result, they remain on the surface of the skin, leading to the formation of Fordyce spots.

**Why Each Wrong Option is Incorrect**
* **Option A:** Fordyce spots are not caused by an infection, as they are a benign condition and not a sign of an underlying infectious process.
* **Option B:** Fordyce spots are not a type of skin cancer, as they are a normal variant of sebaceous glands and not a malignant condition.
* **Option C:** Fordyce spots are not a sign of a systemic disease, as they are a localized condition and not a symptom of a broader medical condition.

**Clinical Pearl / High-Yield Fact**
Fordyce spots are a common and harmless condition, but they can be a source of embarrassment or concern for some individuals. They are more noticeable in individuals with darker skin types, as they are more easily visible against the skin.

**Correct Answer: D. Benign ectopic sebaceous glands.**