What should you know about LCIS and tamoxifen?

LCIS is a lobular cell change that signals increased future breast cancer risk. Tamoxifen is a selective oestrogen receptor modulator: it blocks oestrogen activity in breast tissue. For some people, this makes it a risk-reduction option even when there is no invasive cancer to treat. It is different from chemotherapy and is not a treatment that removes LCIS already seen on a biopsy.

Tamoxifen can affect other tissues, so the choice should account for menstrual status, clotting history, medicines, pregnancy plans, uterine health, and symptoms that matter to you. The expected benefit is weighed against side effects and uncommon but serious risks.

Ask the prescriber how tamoxifen would change your individual risk and how long they recommend taking it. Review all medicines, supplements, and contraceptives because some products can interfere with tamoxifen or add clotting risk. Common effects can include hot flushes, night sweats, vaginal symptoms, mood changes, or changes in periods. Do not stop treatment abruptly without contacting the prescribing team; they may suggest a different approach if symptoms are difficult.

Continue the breast surveillance plan advised after LCIS. Tamoxifen does not replace imaging or clinical review, and it does not prevent every type of breast cancer.

Seek urgent medical help for sudden chest pain, breathlessness, coughing blood, one-sided leg swelling or pain, sudden weakness, or trouble speaking. Contact your clinician about unusual vaginal bleeding, new pelvic pain, severe headaches, or vision changes. Report a new breast lump, nipple discharge, or skin change through your breast service.

What benefit might tamoxifen offer me? Which side effects need action? Do my medicines or family history change the choice? What contraception is suitable? How will breast and gynaecological follow-up be arranged?