Table 1.

Main clinical and pathological characteristics studied.

	HER2-low (n = 192)	HER2-zero (n = 140)
Age, years (SD)	57 (14)	58 (14)
PAM50 subtype, n (%)
Luminal A	114 (60.0)	78 (55.7)
Luminal B	73 (38.4)	59 (42.1)
HER2-enriched	2 (1.0)	2 (1.4)
Basal-like	1 (0.6)	1 (0.8)
Risk group, n (%)
Low	56 (29.5)	37 (26.4)
Intermediate	62 (32.6)	55 (39.3)
High	72 (37.9)	48 (34.3)
ROR, mean (SD)	44 (21)	45 (19)
Ki-67, n (%)
Low (<20%)	96 (51.0)	59 (42.5)
High (≥20%)	92 (49.0)	80 (57.5)
PR, n (%)
<20%	59 (30.7)	30 (21.6)
≥20%	133 (69.3)	109 (78.4)
Histology, n (%)
Ductal	144 (75.8)	108 (77.1)
Lobular	40 (21.0)	25 (17.9)
Others	6 (3.2)	7 (5.0)
Histological Grade, n (%)
Low/1	32 (17.0)	24 (17.4)
Intermediate/2	116 (61.7)	84 (60.9)
High/3	40 (21.3)	30 (21.7)
T stage, n (%)
T1	109 (56.8)	82 (58.6)
T2	77 (40.1)	52 (37.1)
T3	6 (3.1)	6 (4.3)
N stage, n (%)
N0	113 (58.9)	83 (59.3)
Nmic	29 (15.1)	21 (15.0)
N+	50 (26.0)	36 (25.7)
Menopausal status, n (%)
Premenopausal	56 (29.5)	43 (31.8)
Postmenopausal	135 (70.5)	96 (68.2)