Sequential occurrence of different subtypes of nonpuerperal mastitis in contralateral breasts: a report of two cases

Nonpuerperal mastitis (NPM) is a nonspecific chronic inflammation in the breast. The two most common pathologic subtypes are idiopathic granulomatous mastitis (IGM) and plasma cell mastitis (PCM). The cause of NPM is unknown, and the recurrence rate is high; however, the sequential development of two different pathologic subtypes of NPM in contralateral breasts of the same patient is rare.

Two women who were in their 30 s and with a history of childbearing had an inflammatory mass in one breast, which was identified as PCM by core needle biopsy. However, 1 year after treatment, IGM occurred in the contralateral breast. Histopathologic results after the surgery confirmed both diagnoses. New-onset PCM in both patients was successfully treated with local extended surgical resection and antibiotics combined with incision and drainage. The IGM that developed in the contralateral breast after 1 year was treated with local extended surgical resection and oral steroids. No signs of NPM recurrence were observed in either breast after a follow-up period of more than 1 year.

Because recurrence after NPM treatment often occurs in the affected breast, the contralateral breast, which does not often exhibit morbidity factors, is often ignored during treatment follow-up. However, our cases suggest that patients with the occurrence of NPM in one breast should undergo long-term follow-up of the contralateral breast by close monitoring. NPM recurrence should also be considered when there is pain, redness, and swelling in the contralateral breast.