Table 1 Clinicopathologic characteristics and germline genetic alterations of study cohort

Clinical presentation

Palpable mass

13/38 (34%)

Mammographically-detected mass/asymmetry

13/38 (34%)

Mammographically-detected calcifications

3/38 (8%)

MRI-detected

9/38 (24%)

Personal breast cancer history

9/38 (24%)

Personal non-breast cancer history

7/38 (18%)

Family breast cancer history

24/38 (63%)

Family breast cancer history (1^st degree relative)

14/38 (37%)

Germline pathogenic/likely pathogenic variant

16/38 (42%)

BRCA1

13/16 (81%)

BRCA2

2/16 (13%)

PALB2

1/16 (6%)

Type

IBC-MGA

34/38 (89%)

BCis-MGA

4/38 (11%)

Median invasive tumor size, mm (range)^a

15 (2-55)

Histologic type

IDC-NST

20/34 (59%)

Matrix-producing metaplastic carcinoma

11/34 (32%)

Ductal with acinic cell features

2/34 (6%)

Spindle cell metaplastic carcinoma

1/34 (3%)

Nottingham grade^b

1–2

6/34 (18%)

3

28/34 (82%)

LVI identified

7/38 (18%)

Lymph node metastasis

7/33 (21%)

Tumor-infiltrating lymphocytes (%)

<50

29/34 (85%)

> = 50

5/34 (15%)

Neoadjuvant chemotherapy

11/34 (32%)

Pathologic complete response

2/11 (18%)

Surgical treatment

Breast conservation

17/38(45%)

Mastectomy

21/38 (55%)

IBC-MGA with clinical follow up

31/34 (91%)

Median follow-up in months (range)

64 (35−238)

Adjuvant radiotherapy

21/31 (68%)

Adjuvant chemotherapy

24/31 (77%)

Local recurrence

1/31 (3%)

Distant metastasis

5/31 (16%)