From: Skin invasion and prognosis in node negative breast cancer: a retrospective study
 |  | Case | Control |  | ||
---|---|---|---|---|---|---|
Operation | Total mastectomy | 90 | (92.8%) | 3504 | (77.9%) | p < 0.001 |
 | Partial mastectomy | 7 | (7.2%) | 963 | (21.4%) |  |
 | Unknown | 0 | (0%) | 33 | (0.7%) |  |
Number of removed | Median | 22 | Â | 22 | Â | p = 0.630 |
lymph nodes | Range | 5–70 |  | 5–125 |  |  |
Chemotherapy | Yes | 28 | (30.0%) | 1051 | (23.4%) | p = 0.127 |
 | No | 69 | (70.0%) | 3449 | (76.6%) |  |
Endocrine | Yes | 40 | (41.2%) | 1591 | (35.4%) | p = 0.138 |
therapy | No | 57 | (58.8%) | 2909 | (64.6%) | Â |
Radiation therapy | Yes | 3 | (3.1%) | 359 | (8.0%) | p = 0.081 |
 | No | 93 | (96.9%) | 4141 | (92.0%) |  |