**Core Concept**
Cystic disease of the breast refers to the presence of fluid-filled cysts within the breast tissue, which can be benign or malignant in nature. This condition is often associated with fibrocystic changes, a common benign breast condition characterized by fibrosis and cyst formation.

**Why the Correct Answer is Right**
Cystic disease of the breast typically presents as a palpable, painless mass or a collection of masses. The cysts are usually filled with serous fluid and can vary in size. On imaging studies, such as ultrasound or mammography, cystic lesions appear as well-defined, fluid-filled structures without solid components. The correct answer is related to the typical presentation and imaging characteristics of cystic disease of the breast.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the typical presentation of cystic disease of the breast. Cystic lesions are often painless, not painful.
**Option B:** This option is incorrect as it does not specifically relate to the imaging characteristics of cystic disease of the breast. While mammography can be useful, ultrasound is often the preferred imaging modality for evaluating breast cysts.
**Option C:** This option is incorrect as it does not accurately describe the typical composition of cystic lesions in the breast. Cysts are usually filled with serous fluid, not pus.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that most breast cysts are benign and resolve spontaneously. However, it's crucial to evaluate any new or changing breast mass thoroughly, including imaging studies and fine-needle aspiration, to rule out malignancy.

**Correct Answer:**