What condition requires medical referral and involves a sac that can be drained of fluid?

Cysts are closed sacs that can be filled with fluid, semi-solid material, or gas, and they can develop anywhere in the body, including the skin. When a cyst is present, it's essential to assess its characteristics, size, and location. In many cases, if a cyst appears inflamed, painful, or shows signs of infection, medical referral is necessary for proper evaluation and possible drainage. Draining a cyst usually requires expertise to minimize the risk of infection and ensure proper healing.

In contrast, macules are flat, discolored areas on the skin that do not involve any fluid-filled sacs. Pustules are small, inflamed bumps filled with pus, typically associated with acne or infections, and may not require medical referral unless there's a severe infection. Nodules are solid, raised formations beneath the skin's surface that may be benign or malignant, but they do not involve the same fluid-filled characteristics as cysts and often do not require drainage.