Lactating adenomas are benign breast tumours that typically occur in the peri-partum period, and are one of the most prevalent breast lesions during puerperium 4.
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Clinical presentation
Lactating adenomas commonly present as painless breast masses late in pregnancy or in the postpartum period. They are often palpable, mobile lesions that undergo rapid growth and may be large in size.
Lactating adenomas resolve or decrease in size in the postpartum period or with cessation of lactation but may recur during subsequent pregnancies.
Pathology
They fall under adenomatous breast lesions. They are thought to occur in response to the physiological changes of pregnancy and during lactation and is likely due to rising oestrogen levels. Grossly, it is usually rubbery or firm and has a yellow to tan-colour with a lobulated cut surface. Histopathologically, a lactating adenoma is a well-circumscribed lesion composed of secretory lobules separated by delicate connective tissue.
Location
There may be a predilection towards the anterior portion of the breast.
Associations
There are occasional reports of co-existing malignancy such as invasive ductal carcinoma 3,5.
Radiographic features
Ultrasound
Ultrasound is the initial imaging modality of choice especially considering the patient demographics.
Ultrasound features of a lactating adenoma can be variable 1. In general, the features are benign; however, some characteristics can mimic malignancy:
- most lactating adenomas have sharp margins
- most are homogeneous and hypoechoic/isoechoic
- may contain large cystic areas representative of infarction and necrosis
- most have posterior acoustic enhancement
- approximately 20-33% of cases may show compressibility
Echogenic bands may be seen coursing through the mass, which corresponds to fibrotic bands seen histologically.
Mammography
May be seen as a well-defined lobulated breast mass and may have radiolucent central areas. They are sometimes seen as an asymmetrically increased density 8.
Treatment and prognosis
They are benign lesions and classically undergo spontaneous regression after pregnancy and lactation. However, a core biopsy is recommended for tissue sampling given their resemblance to other pathological entities.
Bromocriptine has been used to reduce the size of a lactating adenoma by suppressing prolactin secretion.
Complications
- development of a milk fistula following core biopsy
- they can cause development of foci of infarction of breast tissue 3
Differential diagnosis
General imaging differential considerations include:
- fibroadenoma
- galactocele: no colour flow on ultrasound
- breast lymphoma
On ultrasound appearances there can be some imaging overlap with pregnancy-associated breast cancer.
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