Table 2. Clinicopathological characteristics of cases involving secondary contralateral breast tumours.

	Clinical characteristics								Pathological characteristics		Molecular characteristics
	First tumour			Second tumour					First tumour	Second tumour	HUMARA	GAMDDL
Case	Location	pTNM	Adjuvant Therapy	Loation	pTNM	Time to 2nd tumour (M)	Adjuvant Therapy	Outcome	IIS, HG/NG	IIS, HG/NG	First/second tumours	First/second tumours
9	Left	T1micN0		Right	Tis	7	AI	Alive	Luminal A, NG2	Luminal A, NG2	NP	No mutation
10	Right	T1N0	Tam	Left	T1micN0	24		Alive	BLBC, HGI	HER2, NG3	NP	Different mutation
11	Left	T1N0	Tam	Right	T1N0	51		Alive	Luminal A, HGI	Luminal A, HGI	Same allele	Different mutation
12	Left	T1N0	IR, Tam	Right	T1micN0	34	AI	Alive	Luminal A, HGI	TNBC, NG3	Same allele	Different mutation
13	Right	T1N0		Left	Tis	0		Alive	Luminal A, HGI	Luminal A, NG2	Same allele	Different mutation
14	Right	T1N0	Tam	Left	T1mic	67		Alivea	Luminal A, HGI	Luminal A, NG1	Different allele	NE
15	Right	T1N1	Tam	Left	T1mic	14		Alive	Luminal A, HGII	TNBC, NG3	Different allele	NE
16	Right	T1N1		Left	T1N1	47	CMF	Alive	BLBC, HGIII	BLBC, HGIII	Different allele	NE
17	Right	T2N1		Left	T1	18		Alive	Luminal A, HGI	Luminal A, HGI	Different allele	NE
18	Right	T2N0		Left	T2N0	36	IR	Alive	Luminal A, HGII	Luminal A, HGIII	Different allele	NE
19	Right	T1N0		Left	T1	28	IR, CMF	Alive	Luminal A, HGI	Luminal A, HGII	Different allele	NE

^aWith lung metastasis.

Abbreviations: AI=aromatase inhibitor; BLBC=basal-like breast cancer; CMF=CPM+methotrexate+5-FU; GAMDDL=gene alterations of mitochondrial DNA D-loop region; HG=histological grade I, II, and III; HUMARA=human androgen receptor; IR=irradiation; IIS=immunohistochemical intrinsic subtype; M=months; NE=not examined; NG=nuclear grade 1, 2, and 3; NP=no polymorphism; Tam=tamoxifen; TNBC=triple-negative breast cancer.