The most common symptom of a malignant breast tumour in pre-menopausal women is the appearance of a non-painful lump: more rarely the first sign is a palpable axillary node. It is of course difficult to distinguish a benign nodule (typically a fibroadenoma) from cancer based on physical examination, and clinicians must always keep in mind the possibility of a non-benign lesion.

A growing nodule in the breast is difficult to interpret in a pregnant woman, when the whole body and the breasts in particular undergo relevant changes in size and in consistency. The low incidence of breast cancer in young women and, in a certain sense, the more or less unconscious refusal of diagnosing a malignant tumour in a pregnant woman will often result in a missed or delayed diagnosis.

Ionising radiations are among the best known mutagenic and teratogenic agents: their use during pregnancy should be limited to a minimum, or rather avoided whenever possible. Mammography using a radiological shelter to protect the uterus is feasible and safe for the foetus: this technique has the highest sensitivity to detect microcalcifications. Its use in pre-menopausal women is however less effective than in older patients. In pregnant women this exam can generally be postponed and performed after delivery. Contrast agents also raise some concerns about safety for the foetus. We therefore totally agree that in pregnant women “imaging should be used … only when the benefits outweigh the risks” [38].

Even if ultrasound scans do not have any role in screening, they provide a detailed evaluation of size and of other characteristics of breast nodules. Furthermore, Doppler techniques add reliable indications on blood flow making a differential diagnosis between benign and malignant lesions easier.

This technique does not involve the use of ionising radiations and is therefore not contraindicated, but the information it provides is generally not essential for treatment and this exam may be avoided in pregnant women with breast cancer. The main issue remains the false-positive rate during pregnancy and the potential foetal toxicity of gadolinium.

A tumour sample suitable for histological examination can be easily obtained by a core needle biopsy. In most cases the amount of tissue is sufficient to perform not only basic histological analysis, but also to obtain information about the biological features of the tumour, such as hormone receptor status, HER2 overexpression or amplification and proliferation rate.

Local anaesthesia implies no danger to the mother nor to the baby, and even general anaesthesia (which is generally not required for diagnostic purposes) can be safely performed during pregnancy.

Fine needle aspiration, due to cellular changes in the breast caused by hormones, may be difficult to interpret and is therefore not recommended [2].

The most reliable evidence on the safety of surgery (and of general anaesthesia) in pregnancy derives from the large number of procedures that have been performed in pregnant women for emergencies. Breast surgery, if clinically indicated, is therefore feasible. The reason why surgical removal of breast cancer is generally not performed during pregnancy is linked to the treatment strategy that is preferentially based on a pre-operative (neoadjuvant) chemotherapy. Surgery is therefore often delayed and performed after delivery. Not only is breast surgery feasible during pregnancy: it must be stressed that any type of procedure is possible. There is no reason to consider mastectomy as the procedure of choice: partial breast removal, if indicated, can be safely performed in a pregnant woman. Radiotherapy to the breast (and to adjacent tissues if indicated) can then be safely delayed and administered after delivery (see below).

Sentinel lymph node analyses performed in non-pregnant women showed that the dose of radiation that the foetus would receive as a consequence of radioactive identification of an axillary lymph node is very low [15, 16, 34], so there is no reason to withhold this procedure in pregnant women if clinically indicated.

Radiotherapy has evident mutagenic and teratogenic effects that are particularly dangerous in the first trimester [19]. Concerning breast cancer treatment, in principle it is possible to administer radiotherapy to the breast and effectively shield the uterus and therefore the baby, but this is not performed in clinical practice. What we actually see is that pregnant women receive adjuvant chemotherapy after surgery for 12–16 weeks. Similarly to what is implemented in non-pregnant women, adjuvant radiation is preferentially administered after the end of chemotherapy and therefore after delivery.

Most traditional anticancer agents act by inhibiting the proliferation of malignant cells, but they cannot distinguish between normal and cancer cells. Foetal growth is mostly due to processes of cell proliferation that are identical to those used by cancer cells. Foetal tissues are therefore especially sensitive to antiproliferative treatment [20]. Even agents that have no antiproliferative activity may cause serious damages to the developing baby. Thus, it is easy to understand that for a long time doctors refused to administer chemotherapy, or specific anticancer agents [21], to pregnant women.

Nonetheless, this principle has been challenged in recent years [22].