Table 1.

Clinical characteristics of bilateral breast cancer patients.

BBC (n = 139)	No. Patients (%)
Tumor description
Metachronous	93 (66.9%)
Synchronous	46 (33.1%)
Sex
Female	137
Male	2
Age at diagnosis (years)
Primary tumor
Median (range)	45 (21–77)
≤40	41 (29.5%)
41–50	53 (38.12%)
51–60	29 (20.9%)
≥60	16 (11.5%)
Secondary tumor
Median (range)	51 (21–80)
≤40	21 (15.1%)
41–50	48 (34.5%)
51–60	40 (28.8%)
≥60	30 (21.6%)
Time between 1st and 2nd tumors (years)
Median ± DS	4 ± 6.08
≤5	88 (63.3%)
6–10	27 (19.4%)
>10	24 (17.3%)
Histology 1st breast cancer
Ductal in situ	96 (69%)
Ductal invasive	13 (9.4%)
Lobular invasive	12 (8.6%)
Others	18 (13%)
Histology 2nd breast cancer
Ductal in situ	16 (11.5%)
Ductal invasive	92 (66.2%)
Lobular invasive	15 (10.8%)
Others	16 (11.5%)
Molecular phenotype 1st breast cancer
Luminal A	28 (20.1%)
Luminal B/HER2 -	49 (35.3%)
Luminal B/HER2 +	7 (5%)
HER2 + (non-luminal)	6 (4.3%)
Triple negative	12 (8.6%)
Unknown	37 (26.7%)
Molecular phenotype 2nd breast cancer
Luminal A	35 (25.2%)
Luminal B/HER2 -	35 (25.2%)
Luminal B/HER2 +	10 (7.2%)
HER2 + (non-luminal)	5 (3.6%)
Triple negative	17 (12.2%)
Unknown	37 (26.6%)
Genetic testing results
Pathogenic variant BRCA1	13 (9.3%)
Pathogenic variant BRCA2	19 (13.7%)
Pathogenic variant BRCA1/BRCA2	1 (0.7%)
Pathogenic variant CHEK2	5 (3.6%)
Pathogenic variant PALB2	8 (5.8 %)
Pathogenic variant ATM	3 (2.2%)
Pathogenic variant PTEN	1 (0.7%)
Pathogenic variant RAD51C	2 (1.4%)
Pathogenic variant MUTHY	1 (0.7%)
Variant of uncertain significance	27 (19.4%)
Negative	59 (42.5%)
Type of surgery 1st breast cancer
Mastectomy	50 (36.2%)
Breast conserving therapy	74 (53.2%)
Unknown	15 (10.9%)
Type of surgery 2nd breast cancer
Mastectomy	48 (34.5%)
Breast conserving therapy	55 (39.9%)
Unknown	35 (25.3%)