Mutational landscape differences between young-onset and older-onset breast cancer patients

BMC Cancer

Table 1 Tumour subtypes across age of onset groups

Tumour Type	Young	Older	Oldest	Total	p-value (young vs. older)	p-value (young vs. oldest)
Basal-like	17 (22%)	129 (16.7%)	45 (12%)	146 (17.1%)	0.27	0.03*
HER2+	3 (4%)	66 (8.5%)	27 (7%)	69 (8.1%)	0.19	0.33
Luminal A	39 (50%)	393 (50.8%)	219 (59%)	432 (50.7%)	0.91	0.17
Luminal B	18 (23%)	164 (21.2%)	75 (20%)	182 (21.4%)	0.67	0.54
Normal-like	1 (1%)	22 (2.8%)	6 (2%)	23 (2.7%)	0.71	1.00

Frequency and proportion of tumours in each age of onset group of each PAM50 tumour subtype. Entries are the number of samples of each subtype (% of samples in age of onset group). The p-values were calculated using Fisher’s exact test (* indicates statistical significance at the 0.05 level). Age of onset groups were defined as “Young”: breast tumours diagnosed at ≤40 years of age (n = 78), “Older”: breast tumours diagnosed > 40 years of age (n = 774), and “Oldest”: breast tumours diagnosed > 60 years of age (n = 372). HER2+: human epidermal growth factor receptor 2 over-expressing; PAM50: prediction analysis of microarrays 50 gene set

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