Galactocele is a retention cyst containing milk products (fat, protein, lactose) that forms as a result of obstruction of milk ducts during the lactational or post-lactational period. It most commonly occurs during breastfeeding or in the weeks after breastfeeding cessation. Histologically, it consists of one or more dilated ducts filled with milky or creamy material. Clinically presents as a soft, palpable, painless or mildly tender mass. May demonstrate pathognomonic fat-fluid level on mammography — this finding distinguishes galactocele from all other breast lesions. It is a benign condition and usually shows spontaneous resolution or is treated with simple aspiration.
Age Range
20-40
Peak Age
30
Gender
Female predominant
Prevalence
Uncommon
Galactocele forms as a result of milk duct obstruction from various causes (mechanical obstruction, inflammation, congenital anomaly). During lactation, while active milk production continues, ductal obstruction leads to accumulation of milk products in the proximal duct. The accumulated milk undergoes changes over time: initially homogeneous liquid milk, fat globules (creamy layer) and protein-lactose mixture (watery layer) separate under gravity → creating pathognomonic fat-fluid level on mammography. The density of the fat component (-30 to -100 HU) is lower than water and positions superiorly; the protein-water mixture remains inferior. The US appearance of galactocele depends on the stage of its contents: fresh milk appears anechoic/hypoechoic, fat crystallization creates echogenic foci, and old galactoceles may appear completely hyperechoic (inspissated/dried milk). On MRI, fat content is reflected as high signal on T1-weighted images and shows signal loss on fat-suppressed sequences — proving the presence of intralesional fat. In infected galactoceles, bacterial invasion can lead to secondary inflammation and create an abscess-like appearance.
Fat-fluid level within the mass on lateral mammographic view reflects the separation of milk fat and protein-water mixture under gravity and is pathognomonic for galactocele. No other breast lesion demonstrates this finding. Movement of the level when patient position changes confirms the diagnosis.
Fat-fluid level is seen within the mass on lateral mammographic view (or true lateral position). Fat density (radiolucent/dark) is at the top, water/protein density (more opaque) at the bottom. This level creates a horizontal and clear interface. The presence of the level can be confirmed by showing the level shifting on images taken in different positions. This finding is pathognomonic for galactocele.
Report Sentence
A fat-fluid level is seen within the mass on lateral mammographic view; this finding is pathognomonic for galactocele diagnosis in the lactational/post-lactational context.
May also appear as a completely or partially fat-density mass without fat-fluid level. Homogeneous fat-density galactoceles are evaluated in the differential diagnosis of fat-containing lesions (lipoma, fat necrosis, hamartoma). A thin, smooth capsule may be present. Calcification is not typical. Mixed-density galactoceles show a combination of fat and soft tissue density.
Report Sentence
A well-circumscribed, fat-density mass is seen on mammography; galactocele should be the leading consideration in the lactational context.
US appearance of galactocele shows a wide spectrum depending on the stage of contents: (1) Fresh milk — anechoic or hypoechoic with low-level echoes, simple cyst-like, posterior acoustic enhancement (+). (2) Partially inspissated — mixed echogenicity, fat-fluid level may also be seen on US, internal echoes present. (3) Completely inspissated — hyperechoic or heterogeneous solid appearance, posterior acoustic shadowing may be present. Typically oval, well-circumscribed, compressible. No vascularity on Doppler.
Report Sentence
A well-circumscribed, oval, compressible cystic lesion containing internal echoes is seen in the breast parenchyma, consistent with galactocele in the lactational context; no vascularity is detected on Doppler examination.
Galactocele demonstrates high signal intensity on T1-weighted images — due to milk fat content. Signal loss is seen on fat-suppressed sequences (STIR or fat-sat T1), proving intralesional fat presence. Fat-fluid level may also be visible on T1 (high signal fat above, intermediate signal fluid below). On contrast-enhanced MRI, wall enhancement is absent or minimal — distinguishing from malignant processes.
Report Sentence
The mass demonstrates high signal intensity on T1-weighted images with signal loss on fat-suppressed sequences; this finding is consistent with intralesional fat content and strongly suggests galactocele in the lactational context.
On CT (rarely needed, usually incidental), galactocele appears as a fat-density (-30 to -100 HU) mass. Fat-fluid level may also be visible on CT. Thin, smooth wall and absence of calcification is typical. Shows no enhancement or very mild wall enhancement. These findings should be distinguished from lipoma or oil cyst (fat necrosis).
Report Sentence
A well-circumscribed, fat-density (-XX HU) cystic lesion without enhancement is seen in the breast parenchyma on CT; consistent with galactocele in the context of lactational history.
Criteria
During active lactation, contains homogeneous liquid milk. Simple cyst appearance on US as anechoic or hypoechoic with low-level echoes.
Distinct Features
Isodense or water-density mass on mammography. Fat-fluid level may not have developed yet. White milk obtained on aspiration. Usually resolves without treatment.
Criteria
In post-lactational period, contains concentrated milk products with water absorption. Creamy or semi-solid content.
Distinct Features
Fat-density or fat-fluid level mass on mammography. Mixed or hyperechoic appearance on US. Creamy material obtained on aspiration. Mammography may be diagnostic.
Criteria
Secondary infection of galactocele. Clinically accompanied by pain, erythema, fever. May take on abscess-like appearance.
Distinct Features
Wall thickening and surrounding edema are added on US. Perilesional hypervascularity develops on Doppler. Antibiotic + drainage may be needed. Inflammatory findings are superimposed on galactocele findings.
Distinguishing Feature
Simple cyst appears as water-density mass on mammography (no fat density, no fat-fluid level). Meets simple cyst criteria on US as anechoic with posterior enhancement. Galactocele shows low density or fat-fluid level on mammography due to fat content.
Distinguishing Feature
Fat necrosis can also show fat-containing lesion on mammography (oil cyst) but usually has trauma/surgical history and calcification (thin rim or coarse calcification) may accompany. Galactocele occurs in the lactation context and does not show calcification.
Distinguishing Feature
Hamartoma shows a mixture of fat and soft tissue density with a thin capsule in a 'breast-within-breast' appearance on mammography. Galactocele is a single-compartment cystic lesion showing fat-fluid level. Hamartoma is not related to lactation.
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
no-follow-upGalactocele is a completely benign condition. Most galactoceles resolve spontaneously — especially after breastfeeding cessation. US-guided aspiration is sufficient for symptomatic galactoceles (pain, cosmetic concern, infection risk). Aspiration typically yields milk or creamy material — cytology is benign. Recurrence is possible but repeat aspiration is sufficient. Surgery is rarely needed. No malignancy risk. Fat-fluid level on mammography is pathognomonic and does not require biopsy.
Galactocele is a benign lesion that usually resolves spontaneously. No treatment required. Aspiration may be performed for large or symptomatic lesions. Infected galactocele may lead to abscess formation.