Male breast cancer is rare, hormone-driven, and diagnosed too late

Breast cancer in men is rare — men make up less than 1% of all breast cancers — but it is a real disease that tends to be caught later and at a higher stage than in women, and is almost always hormone-driven [s1][s3]. Survival has improved over the decades, though more slowly for men than for women, and because dedicated trials in men barely exist, treatment is largely extrapolated from female breast cancer [s2][s3].

What the population data show

The most complete population picture comes from the US National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) programme, analysed across breast cancers diagnosed from 1973 through 2005 [s3]. Of all breast cancers in that dataset, men accounted for less than 1% [s3]. Compared with women, male breast cancers occurred later in life, at higher stage, with lower grade, and were more often oestrogen-receptor positive [s3].

The trend over time is encouraging but uneven. Comparing men diagnosed in 1996–2005 with those in 1976–1985, and adjusting for age, stage and grade, the risk of dying from breast cancer fell by 28% (P=.03) [s3]. Over the same span the decline for women was steeper, at 42% [s3]. In other words, outcomes have improved for both sexes, but progress for men has lagged — a pattern the authors attribute partly to later diagnosis and partly to how little of the research effort has been directed at men [s3].

An overwhelmingly hormone-receptor-positive disease

The biology was pinned down by the International Male Breast Cancer Program, a retrospective joint analysis by the EORTC and partners of men treated between 1990 and 2010 across 93 centres in nine countries [s1]. Of 1,822 patients enrolled, 1,483 were analysed; the median age at diagnosis was 68.4 years, and 5.1% already had metastatic disease [s1].

Central pathology confirmed how consistently hormone-driven the disease is. Among non-metastatic tumours, 99.3% were oestrogen-receptor positive, 81.9% progesterone-receptor positive, and 96.9% androgen-receptor positive [s1]. Most — 84.8% — were invasive ductal carcinomas, and by immunohistochemistry 41.9% were Luminal-A-like and 48.6% Luminal-B-like/HER2-negative, with only 8.7% HER2-positive and 0.3% triple-negative [s1]. Better survival tracked with strongly receptor-positive disease [s1].

The analysis also exposed a treatment gap. Although 56.2% of non-metastatic tumours were node-negative and 48.5% were small T1 lesions, only 4% of men had breast-conserving surgery, against 18% who had a sentinel-lymph-node biopsy [s1]. And while more than 90% of tumours were oestrogen-receptor positive, only 76.8% of men received adjuvant endocrine therapy — the treatment most likely to help a hormone-driven cancer — of whom 88.4% were given tamoxifen [s1].

How men are actually treated

Because trials in men are so scarce, the American Society of Clinical Oncology built its 2020 guideline on 26 descriptive or observational studies and a formal consensus process, and much of it maps female-breast-cancer practice onto men [s2]. For men with hormone-receptor-positive disease who are candidates for adjuvant endocrine therapy, ASCO recommends tamoxifen for an initial five years; those who tolerate it and remain at high risk may be offered a further five years [s2]. An aromatase inhibitor is reserved for men who cannot take tamoxifen, and then only combined with a drug that suppresses testicular hormone production [s2].

The guideline's other recommendations are worth knowing. Men treated with lumpectomy should be offered an annual mammogram of the treated side; routine breast MRI is not recommended [s2]. Early-stage disease should not be treated with bone-strengthening drugs to prevent recurrence, though those agents can still be used to treat or prevent osteoporosis [s2]. And ASCO advises that every man diagnosed with breast cancer be offered genetic counselling and germline testing of cancer-predisposition genes — a reflection of how often inherited mutations underlie the disease in men [s2].

The practical message is not to screen men for breast cancer — there is no such programme — but to take a new breast lump, skin change or nipple discharge in a man seriously rather than assuming breast cancer is a women's disease [s1]. For a benign condition men more commonly notice in the same tissue, see our review of gynecomastia; for how the receptor-positive biology drives treatment in women, see hormone therapy after breast cancer and what breast-density notifications mean.

This article is informational and is not medical advice. A new breast or nipple change should be evaluated by a clinician.