Invasive breast cancers in adolescent and young adult women show more aggressive immunohistochemical and clinical features than those in women aged 40-44 years.

BACKGROUND: Limited knowledge exists concerning the clinicopathological features of breast cancers (BCs) occurring in adolescent and young adult (AYA) women. We evaluated tumor characteristics in AYA women in comparison with those in middle-aged premenopausal women.

METHODS: From consecutive AYA patients (< 35-year-old) with invasive BC in a single institute, 82 patients first treated with surgery were examined. As the control group, 82 tumors from middle-aged premenopausal patients (40-44 years) were selected by matching pathological T and N factors. We compared habitual factors, immunohistochemical parameters, and patient outcome between the two groups.

RESULTS: Most of the study population (148 of 164, 90.2%) were in the early clinical stages (stage I or II). In the AYA group, the number of childbirths was smaller (p < 0.0001), while the volume of alcohol consumption was larger (p < 0.0001), and palpable primary tumors were more frequent (p < 0.01) than in the control group. The positivities of estrogen receptor, progesterone receptor, and androgen receptor were lower (p < 0.001, p = 0.03, and p < 0.001, respectively), and the triple-negative (TN) BCs rates were higher (p < 0.01) in the AYA group. Distant recurrence-free survival (DRFS) curves were different in the whole population (p = 0.02) and in hormone receptor-positive cases (p = 0.01).

CONCLUSIONS: We confirmed that BCs occurring in AYA women had more aggressive features than those of the older premenopausal women in terms of a high proportion of TN subtypes and a lower DRFS.