Malignancy in pregnancy

It is a Tuesday in the antenatal clinic. A 36-year-old woman at 18 weeks' gestation is referred with a 3 cm breast lump found at booking, attributed for the last six weeks to pregnancy-related changes. The cytology came back atypical. Every delay in this woman's diagnosis is a delay in her prognosis — and yet the first question her obstetrician asks is usually the wrong one ("will the treatment harm the baby?"). The right question is whether her pregnancy is being treated alongside her cancer, or instead of it. Modern guideline frameworks reframe the whole field around that question: pregnancy is not a contraindication to cancer treatment.^[1][4]

Overview and definition

Cancer in pregnancy is cancer diagnosed between conception and delivery. The broader term pregnancy-associated cancer includes cancers diagnosed during pregnancy and up to 12 months postpartum — but the postpartum-inclusive definition has been called outdated for breast cancer, because postpartum breast cancer has a distinct biology and prognosis from breast cancer diagnosed during pregnancy.^[1][3]

The incidence is about 1 in 1000 pregnancies, and it is rising in high-income settings — driven by older maternal age, delayed childbearing, and rising early-onset cancer.^[1][2]

The cancers most commonly diagnosed in pregnancy, in approximate order:^[1][2]

• Breast (the most common; the diagnosis that drives the field)
• Cervical (often picked up on abnormal cytology or postcoital bleeding)
• Haematological (Hodgkin and non-Hodgkin lymphoma, acute leukaemia)
• Melanoma (with its unique predilection for placental and fetal metastasis)
• Thyroid and colorectal (rising incidence in young adults)^[2]

Modern consult-series frameworks — and the ESMO 2013 guidelines that predated them — share one principle: cancer treatment in pregnancy is possible and should not be deferred solely because of pregnancy when prognosis is curative. The role of the obstetrician is not to shield the baby from treatment but to enable the woman to be treated.^[1][4]

References19ShowHide

1. [1]Peccatori FA, Azim HA Jr, Orecchia R, et al. Cancer, pregnancy and fertility: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up Ann Oncol, 2013.PMID 23813932
2. [2]de Haan J, Verheecke M, Van Calsteren K, et al. Oncological management and obstetric and neonatal outcomes for women diagnosed with cancer during pregnancy: a 20-year international cohort study of 1170 patients Lancet Oncol, 2018.PMID 29395867
3. [3]Amant F, von Minckwitz G, Han SN, et al. Prognosis of women with primary breast cancer diagnosed during pregnancy: results from an international collaborative study J Clin Oncol, 2013.PMID 23610117
4. [4]Loibl S, Azim HA Jr, Bachelot T, et al. ESMO Expert Consensus Statements on the management of breast cancer during pregnancy (PrBC) Ann Oncol, 2023.PMID 37572987
5. [5]Amant F, Nekljudova V, Maggen C, et al. Outcome of breast cancer patients treated with chemotherapy during pregnancy compared with non-pregnant controls Eur J Cancer, 2022.PMID 35594612
6. [6]Han SN, Amant F, Cardonick EH, et al. Axillary staging for breast cancer during pregnancy: feasibility and safety of sentinel lymph node biopsy Breast Cancer Res Treat, 2018.PMID 29235045
7. [7]Vandenbroucke T, Verheecke M, Fumagalli M, et al. Effects of cancer treatment during pregnancy on fetal and child development Lancet Child Adolesc Health, 2017.PMID 30169185
8. [8]Maggen C, Dierickx D, Lugtenburg P, et al. Obstetric and maternal outcomes in patients diagnosed with Hodgkin lymphoma during pregnancy: a multicentre, retrospective, cohort study Lancet Haematol, 2019.PMID 31564649
9. [9]Borgers JSW, Heimovaara JH, Cardonick E, et al. Immunotherapy for cancer treatment during pregnancy Lancet Oncol, 2021.PMID 34856152
10. [10]LeJeune CL, Van Calsteren K, Baert T, et al. A multidisciplinary management approach to cervical cancer during pregnancy Lancet, 2026.PMID 41720126
11. [11]Khazzaka A, Rassy E, Sleiman Z, et al. Systematic review of fetal and placental metastases among pregnant patients with cancer Cancer Treat Rev, 2022.PMID 35182890
12. [12]Kreuz M, de Souza Wagner PH, Tanimoto LE, et al. Melanoma and pregnant women: a systematic review and meta-analysis Melanoma Res, 2025.PMID 40465258
13. [13]Buonomo B, Brunello A, Noli S, et al. Tamoxifen Exposure during Pregnancy: A Systematic Review and Three More Cases Breast Care (Basel), 2020.PMID 32398983
14. [14]Schuurman TN, Witteveen PO, van der Wall E, et al. Tamoxifen and pregnancy: an absolute contraindication? Breast Cancer Res Treat, 2019.PMID 30707336
15. [15]Berger JC, Clericuzio CL Pierre Robin sequence associated with first trimester fetal tamoxifen exposure Am J Med Genet A, 2008.PMID 18629878
16. [16]Van Assche IA, Van Calsteren K, Lemiere J, et al. Long-term neurocognitive, psychosocial, and physical outcomes after prenatal exposure to radiotherapy: a multicentre cohort study of the International Network on Cancer, Infertility, and Pregnancy Lancet Child Adolesc Health, 2024.PMID 38640941
17. [17]Heesterbeek CJ, Tjan-Heijnen VCG, Heimovaara JH, et al. Prenatal cell-free DNA testing of women with pregnancy-associated cancer: a retrospective cross-sectional study Lancet Reg Health Eur, 2024.PMID 39220433
18. [18]LeJeune CL, Nougaret S, Massera RT, et al. Abdominal shielding not recommended for diagnostic imaging with ionising radiation during pregnancy Lancet Oncol, 2025.PMID 41167213
19. [19]Amant F, Heimovaara JH, Lok CAR, Van Calsteren K The Advisory Board on Cancer, Infertility and Pregnancy: a virtual on-demand multidisciplinary tumour board Lancet Oncol, 2022.PMID 36356601