Final answer:
A galactocele is a milk-filled cyst associated with nursing, typically presenting with well-defined borders and is not generally related to trauma.
Step-by-step explanation:
A galactocele is a milk-filled cyst that is commonly associated with nursing. The correct answer to the question is C. A galactocele is associated with nursing. It forms when a milk duct becomes obstructed during lactation. Galactoceles are typically not related to trauma, meaning option B is incorrect. They are usually radiolucent on radiographic imaging, so option A is not always true—they can be radiopaque due to their milk content. As for their appearance, galactoceles are often smooth and have well-defined borders, rather than irregular, so option D is also incorrect.