Does lump size determine its severity in breast cancer?

Not necessarily : Cancerous breast lump size is very important to define but it's just one part of staging. Severity of the disease also measured by the aggressiveness of the cancerous cell from well differentiated to poorly differentiated. Also hormonal dependent tumor cell as well, meaning that ER positive do better than negative, same with PR and HER2 NEU. Lymph node status is also an extremely important factor

Yes: While size is important and hormone sensitivity and indicator of potenial response. prior to mammograph when lefsion os 5 cm or greater were detected, the overall survival rarely was above 60%. With mammography detecting lesion thatt are virtually non palpable, wide resection has brought the survival rate into the 90% range for most lesions.

Yes, but....: size does matter but there is more than just the size of the mass as stated by the responses. It is important to speak with your surgeon and a plastic surgeon and medical oncologist. In some cases, chemotherapy before surgery may give more surgical options. Good luck!