Table 1 Demographic and clinicopathological characteristics of patient cohort

Ethnicity

Chinese

50 (90.9)

Others

5 (9.1)

Smoking status

Never-smoker

52 (94.5)

Smoker

3 (5.5)

Temporal occurrence of lung and breast cancer diagnosis

Lung cancer occurred first

5 (9.1)

Breast cancer occurred first

38 (69.1)

Synchronous (within 6 months)

12 (21.8)

Family cancer history (any primary)

First degree

27 (49.1)

Second degree

4 (7.3)

No known history

24 (43.6)

Family history of breast and/or lung cancer

First degree

8 (14.5)

Second degree

2 (3.6)

Diagnosis year

1976–2018

Diagnosis year

2005–2018

Median age, years (range)

55 (34–81)

Median age, years (range)

65 (48–78)

Histology

n (%)

Histology

n (%)

Ductal carcinoma in situ (DCIS)

5 (9.1)

Adenocarcinoma (ADC)

44 (80)

Infiltrating ductal carcinoma (IDC)

33 (60)

Neuroendocrine carcinoma

Infiltrating lobular carcinoma (ILC)

4 (7.3)

Carcinoid

2 (3.6)

DCIS + DCIS (bilateral)

1 (1.8)

SCLC

3 (5.5)

IDC + DCIS (bilateral)

2 (3.6)

Undifferentiated

1 (1.8)

IDC + ILC (bilateral)

2 (3.6)

Lymphoepithelioma-like carcinoma (LELC)

1 (1.8)

IDC + unknown subtype (bilateral)

1 (1.8)

ADC + Carcinoid (bilateral, synchronous)

1 (1.8)

Mucinous adenocarcinoma

3 (5.5)

ADC + ADC (bilateral, synchronous)

1 (1.8)

Subtype not specified (NOS)

4 (7.3)

ADC + ADC (same side, synchronous)

2 (3.6)

Staging^a

Staging^b

0

6 (10.9)

0

0 (0.0)

I/II

44 (80.0)

I/II

26 (47.3)

III

4 (7.3)

III

7 (12.7)

IV

1 (1.8)

IV

22 (40.0)

Hormone and HER2 status^c

EGFR status (Adenocarcinoma only, n = 49)

ER

Not tested

4 (8.2)

Positive

36 (65.4)

Tested

45 (91.8)

Negative

10 (18.2)

Mutant

33 (73.3*)

Not tested/unknown

9 (16.4)

Exon19 del

19 (57.6^)

PR

L858R

11 (33.3^)

Positive

30 (54.5)

Others

3 (9.1^)

Negative

15 (27.3)

Wild type

12 (26.7*)

Not tested/unknown

10 (18.2)

HER2

Positive

4 (7.3)

Negative

28 (50.9)

Not tested/unknown/equivocal

23 (41.8)