Final answer:
Nonlactational mastitis can occur in two forms: periductal mastitis, which is linked to smoking and affects the breast ducts, and idiopathic mastitis, which has no identified cause.
Step-by-step explanation:
The two forms of nonlactational mastitis are periductal mastitis and idiopathic mastitis. Periductal mastitis occurs in the ducts of the breast and is most commonly associated with smoking. Idiopathic mastitis, on the other hand, refers to breast inflammation that occurs without a known cause. Both conditions can cause symptoms such as pain, redness, and swelling in the breast area, but they differ in their underlying mechanisms and risk factors.