5.4.0 Special Circumstances

​​​5.4.1 Breast Cancer in Pregnancy

Author: Dr. Alyssa ​Smith
Date of completion: April 2026
Date of next review: May 2027
​​​​See Breast Clinical Care Pathway 

Consider the following in cases of breast cancer during pregnancy:
 
  • Early detection and multidisciplinary management are essential to coordinate care and optimize maternal and fetal outcomes.
  • Standard oncologic principles apply, with pregnancy-specific modifications and timing adjustments:
    • Surgery: safe in all trimesters.
    • Chemotherapy: anthracyclines/taxanes safe in 2nd–3rd trimesters. Dose based on maternal weight.
    • Radiation, endocrine, HER2-targeted, and immunotherapy: defer/avoid until postpartum.
  • Care should be individualized based on gestational age, tumor biology, stage, and patient values.
  • Avoid unnecessary treatment delays or iatrogenic prematurity
  • Frequent maternal-fetal monitoring is recommended.
  • Genetic counseling, psychosocial, and lactation support are integral components of comprehensive care.
 
References
  1. Ruiz R, Herrero C, Strasser-Weippl K, Touya D, St Louis J, Bukowski A, et al. Epidemiology and pathophysiology of pregnancy-associated breast cancer: A review. The Breast. 2017 Oct;35:136‑41. doi:10.1016/j.breast.2017.07.008.
  2. Sun J, Lee MC. Clinical Presentation, Diagnosis and Prognosis of Pregnancy-Associated Breast Cancer. Adv Exp Med Biol. 2020;1252:87-93. doi: 10.1007/978-3-030-41596-9_11. PMID: 32816266.
  3. Boere I, Lok C, Poortmans P, Koppert L, Painter R, van den Heuvel-Eibrink MM, et al. Breast cancer during pregnancy: epidemiology, phenotypes, presentation during pregnancy and therapeutic modalities. Best Pract Res Clin Obstet Gynaecol. 2022;82:46‑59. doi:10.1016/j.bpobgyn.2022.05.001.
  4. Ayyappan AP, Kulkarni S, Crystal P. Pregnancy-associated breast cancer: spectrum of imaging appearances. Br J Radiol. 2010;83(990):529‑34. doi:10.1259/bjr/17982822.
  5. Peterson MS, Gegios AR, Elezaby MA, Salkowski LR, Woods RW, Narayan AK, et al. Breast imaging and intervention during pregnancy and lactation. Radiographics. 2023;43(10):e230014. doi:10.1148/rg.230014.
  6. Amant F, Deckers S, Van Calsteren K, Loibl S, Halaska M, Brepoels L, et al. Breast cancer in pregnancy: recommendations of an international consensus meeting. Eur J Cancer. 2010;46(18):3158‑68. doi:10.1016/j.ejca.2010.09.010.
  7. Blundo C, Giroda M, Fusco N, Sajjadi E, Venetis K, Leonardi MC, et al. Early breast cancers during pregnancy treated with breast-conserving surgery in the first trimester of gestation: a feasibility study. Front Oncol. 2021;11:723693. doi:10.3389/fonc.2021.723693.
  8. Li Y, Wang Y, Sun Q, Shen S. Clinicopathologic features, treatment, and prognosis of pregnancy-associated breast cancer. Front Oncol. 2022;12:978671. doi:10.3389/fonc.2022.978671.
  9. Feng C, Yu D, Qian J. Long-term results and predictors of survival after conservative breast surgery for breast cancer during pregnancy. Med Sci Monit. 2019;25:8587‑94. doi:10.12659/MSM.917288.
  10. Bothou A, Margioula-Siarkou C, Petousis S, Margioula-Siarkou G, Zervoudis S, Sotiriadis A, et al. Sentinel lymph node biopsy for breast cancer during pregnancy: a comprehensive update. Eur J Clin Invest. 2024;54(3):e14134. doi:10.1111/eci.14134.
  11. Mazonakis M, Varveris H, Damilakis J, Theoharopoulos N, Gourtsoyiannis N. Radiation dose to conceptus resulting from tangential breast irradiation. Int J Radiat Oncol Biol Phys. 2003;55(2):386‑91. doi:10.1016/S0360-3016(02)04206-2.
  12. Loibl S, Schmidt A, Gentilini O, Kaufman B, Kuhl C, Denkert C, et al. Breast cancer diagnosed during pregnancy: adapting recent advances in breast cancer care for pregnant patients. JAMA Oncol. 2015;1(8):1145‑53. doi:10.1001/jamaoncol.2015.2413.
  13. Janssen JM, Van Calsteren K, Dorlo TPC, et al. Population pharmacokinetics of docetaxel, paclitaxel, doxorubicin and epirubicin in pregnant women with cancer: a study from the International Network of Cancer, Infertility and Pregnancy (INCIP). Clin Pharmacokinet. 2021;60:775‑84. doi:10.1007/s40262-020-00961-4.
  14. Berends C, Maggen C, Lok CAR, van Gerwen M, Boere IA, Wolters VERA, et al. Maternal and neonatal outcome after the use of G‑CSF for cancer treatment during pregnancy. Cancers (Basel). 2021;13(6):1214. doi:10.3390/cancers13061214.
  15. Sienas L, Wong T, Collins R, Smith J. Contemporary uses of erythropoietin in pregnancy: a literature review. Obstet Gynecol Surv. 2013;68(8):594‑602.
  16. Wolters VERA, Lok CAR, Gordijn SJ, Wilthagen EA, Sebire NJ, Khong TY, et al. Placental pathology in cancer during pregnancy and after cancer treatment exposure. Placenta. 2021;111:33‑46. doi:10.1016/j.placenta.2021.06.003.
  17. Lin Y, Xie X, Wang J, Chen H, Wan N, Lin J. Case report: breast cancer in pregnancy with placental metastasis. Front Oncol. 2025;15:1573915. doi:10.3389/fonc.2025.1573915.
  18. Johnson HM, Miller ME, Mitchell KB, et al. Oncolactation for patients with breast cancer: executive summary from the American Society of Breast Surgeons. Ann Surg Oncol. 2025;32:8720‑7. doi:10.1245/s10434-025-17742-7.
  19. Peccatori FA, Migliavacca Zucchetti B, Buonomo B, Bellettini G, Codacci-Pisanelli G, Notarangelo M. Lactation during and after Breast Cancer. Adv Exp Med Biol. 2020;1252:159-163. doi: 10.1007/978-3-030-41596-9_22. PMID: 32816277.
  20. Amant F, Vandenbroucke T, Verheecke M, Fumagalli M, Halaska MJ, Boere I, et al. Pediatric outcome after maternal cancer diagnosed during pregnancy. N Engl J Med. 2015;373(19):1824‑34. doi:10.1056/NEJMoa1508913.
  21. Vandenbroucke T, Verheecke M, van Gerwen M, Van Calsteren K, Halaska MJ, Fumagalli M, et al. Child development at 6 years after maternal cancer diagnosis and treatment during pregnancy. Eur J Cancer. 2020;138:57‑67. doi:10.1016/j.ejca.2020.07.004.
  22. Amant F, Van Calsteren K, Halaska MJ, Gziri MM, Hui W, Lagae L, et al. Long-term cognitive and cardiac outcomes after prenatal exposure to chemotherapy in children aged 18 months or older: an observational study. Lancet Oncol. 2012;13(3):256‑64. doi:10.1016/S1470-2045(11)70363-1.
  23. Azim HA Jr, Santoro L, Russell-Edu W, Pentheroudakis G, Pavlidis N, Peccatori FA. Prognosis of pregnancy-associated breast cancer: a meta-analysis of 30 studies. Cancer Treat Rev. 2012;38(7):834‑42. doi:10.1016/j.ctrv.2012.06.004.
  24. Amant F, Nekljudova V, Maggen C, Seither F, Neven P, Cardonick EH, et al. Outcome of breast cancer patients treated with chemotherapy during pregnancy compared with non-pregnant controls. Eur J Cancer. 2022;170:54‑63. doi:10.1016/j.ejca.2022.04.014.
  25. Lefrère H, Floris G, Schmidt MK, Neven P, Warner E, Cardonick E, et al. Breast cancer diagnosed in the post-weaning period is indicative for a poor outcome. Eur J Cancer. 2021;155:13‑24. doi:10.1016/j.ejca.2021.06.009.​


5.4.2 Unusual Histologies​

Author: Dr. Nathalie Levasseur & Dr. Christine Simmons
Date of completion: April 2026
Date of next review: May 2027

Variants of Invasive Breast Cancer

There are a number of pathologic variants of invasive breast cancer that are treated the same way as described above for more common invasive ductal or lobular breast cancer, not otherwise specified (NOS).
 
Metaplastic breast cancer refers to situations where the breast cancer cells may be changing or mimicking other types of cancer such as squamous cell carcinoma or osteosarcoma. These tumours are typically lacking ER, PR and HEr2. Tubular, mucinous (colloid), cribriform, and medullary carcinomas are also all variants of invasive carcinoma, that generally hold a more favourable prognosis. Micropapillary carcinomas tend to be more aggressive and are more frequently associated with axillary nodal metastases. As with more common invasive ductal carcinomas NOS, patients with any of these pathologies should be managed initially surgically, with appropriate nodal staging and adjuvant therapy as described above.
 

Phyllodes Tumours of Breast (Cystosarcoma Phyllodes)

See Breast Clinical Care Pathway​

 
These uncommon sarcomas of the female breast arise from the stromal elements. Clinically and on imaging, they may appear very similar to fibroadenomas, although large size and rapid development or growth of the lesion should raise clinical suspicion. Please refer to the clinical care pathway for phyllodes tumours of the breast.
 
References

  1. Lissidini G, Mulè A, Santoro A, Papa G, Nicosia L, Cassano E, et al. Malignant phyllodes tumor of the breast: a systematic review. Pathologica. 2022 Apr;114(2):111‑20. doi: 10.32074/1591-951X-754.
  2. Rodrigues MF, Truong PT, McKevitt EC, Weir LM, Knowling MA, Wai ES. Phyllodes tumors of the breast: The British Columbia Cancer Agency experience. Cancer Radiother. 2018 Apr;22(2):112‑9. doi: 10.1016/j.canrad.2017.08.112.
  3. Rosenberger LH, Thomas SM, Nimbkar SN, Hieken TJ, Ludwig KK, Jacobs LK, et al. Germline Genetic Mutations in a Multi-center Contemporary Cohort of 550 Phyllodes Tumors: An Opportunity for Expanded Multi-gene Panel Testing. Ann Surg Oncol. 2020;27:3633‑40. doi:​​10.1245/s10434-020-08480-z.
  4. Bogach J, Sriskandarajah A, Wright F, Look Hong N. Phyllodes Tumors of the Breast: Canadian National Consensus Document Using Modified Delphi Methodology. Ann Surg Oncol. 2023;30. doi: 10.1245/s10434-023-13912-7.
  5. Bishr MK, Humphreys A, Ahmed M, Cox K, Hughes A, Isherwood J, et al. Contemporary management of phyllodes tumours of the breast: recommendations from the UK Association of Breast Surgery. Br J Surg. 2025 Aug;112(8). doi: 10.1093/bjs/znaf152.