Galactocoeles are the most common benign breast lesion (BIRADS II) that typically occur in young lactating women; however they mostly occur on cessation of lactation 1. They are also sometimes referred to as a lactocoele.
Patients typically present with a painless breast lump occurring over weeks to months. The lesion can present as a single or multiple nodule(s) and can be unilateral or bilateral.
It is essentially a retention cyst resulting from lactiferous duct occlusion. Diagnosis can be achieved with percutaneous aspiration 8. Biochemical analysis of material aspirated from galactocoeles shows variety of proportions of proteins, fat, and lactose. Macroscopically, the milk within the galactocoele may appear white and of usual viscosity if fresh, or thickened if the liquid is older.
There may be predilection towards the sub-areolar region.
Mammographic appearance of galactocoele can be varied depending on the fat and protein content and the consistency of the fluid. Based on these the galactocoeles could appear like a:
Due to significant fat content the mass appears radiolucent.
Fat fluid level within cyst
When fat and water is present and the milk is in fresh liquid state a characteristic fat fluid level is seen due to viscosity difference. This can be demonstrated on mediolateral view with the beam horizontal to the upright patient.
Seen when contents are old milk and water. Due to highly viscous old milk significant separation of fat and water is not possible and hence gives a hamartoma like appearance on mammogram.
Ultrasound appearances can be widely variable. Sonographic characteristics according to one study is as follows 3:
- cystic/multicystic: ~50%
- mixed (cystic + solid): ~37%
- solid: ~13%
Colour Doppler interrogation will show a lack of blood flow.
Secondary infection with development of a breast abscess.
Additional work up
In uncertain cases an aspiration is recommended in the first instance which will classically yield milky fluid 10.
Treatment and prognosis
They are benign lesions and spontaneous resolution occurs in a vast majority of cases. A small percentage have a residual collection that may mimic a fibroadenoma or complex cyst.
History and etymology
The term galactocoele derives from the Greek words galatea meaning milky white and -coele meaning pouch 9.
General considerations on imaging include
- lactating adenoma: seen as a solid lesion and may show colour flow within it
- breast abscess: has a different clinical presentation, but can develop as a complication
- fibroadenoma: classically ovoid or almond shaped with smooth border, internal homogeneous echogenicity and acoustic enhancement 7
- carcinoma of the breast: especially for certain lesions on ultrasound
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