Pregnancy-associated breast cancer

Pregnancy-associated breast cancer = breast cancer diagnosed during pregnancy or within about 1 year after delivery

Key concept: same disease biology, but diagnosed in a hormonally chaotic, medico-legal minefield.

Epidemiology & biology

Roughly 1 in 3,000 pregnancies; one of the commonest pregnancy-related malignancies.
Tends to present later: “it’s just pregnancy/lactation change” → delayed referral.
Often higher stage at diagnosis, more nodal disease, and more often high-grade, hormone-receptor negative and HER2-positive / triple-negative than age-matched controls.
Postpartum cancers (within a few years after delivery) may have particularly aggressive biology, possibly related to involution-associated remodelling.

New palpable mass is the classic story.
Can also present with focal asymmetry, skin/nipple changes, bloody discharge.
Key principle: any persistent palpable mass in pregnancy or lactation must be imaged; do not “watch and wait”.

No radiation; excellent for dense, hormonally stimulated breasts.
Typical findings: irregular hypoechoic mass, angular/spiculated margins, posterior shadowing, possibly abnormal nodes.

Safe in pregnancy with abdominal shielding; foetal dose is tiny and well below harmful levels.
High background density but still useful for calcifications, architectural distortion and multifocality.

Gadolinium generally avoided during pregnancy (crosses placenta).
Postpartum/lactating MRI is possible but background enhancement is often very high; interpret carefully.
DWI can help when contrast is undesirable.

Multidisciplinary planning is mandatory.
Surgery (mastectomy or breast-conserving) is feasible in all trimesters; radiotherapy is deferred until after delivery.
Systemic therapy can be given in 2nd/3rd trimester (no chemo 1st trimester; no trastuzumab or endocrine therapy during pregnancy).
Sentinel node biopsy with Tc-99m alone is increasingly accepted as safe; blue dye is relatively contraindicated.