Authors: Mia Demant, MD, Mia Wagsmo Steffensen, MD

Breast cancer is the most common cancer affecting women and the leading cause of cancer mortality in women worldwide (1). Risk factors include increasing age, reproductive factors (e.g. early menarche, nulliparity, and later onset of menopause all increase the risk of breast cancer), genetic predisposition (e.g. BRCA1 and BRCA2), personal- or family history of breast cancer, and various environmental factors (excessive use of alcohol, obesity and physical inactivity account for 21% of all breast cancer deaths worldwide (2)). Moreover, exogenous hormone exposure (e.g. estrogen treatment in postmenopausal women) increases the risk significantly (3).  

It is currently estimated that approximately 25% of all women who undergo mastectomy also have breast reconstruction performed, and 25% of these women are primarily reconstructed, the others are reconstructed secondarily (4).

TNM classification of breast cancer (1)

Primary tumor (T)
TX	Primary tumor cannot be assessed
T0	No evidence of primary tumor
Tis	Carcinoma in situ
Tis (DCIS)	Ductal carcinoma in situ
Tis (LCIS)	Lobular carcinoma in situ
Tis (Paget’s)	Paget’s disease of the nipple
T1	Tumor ≤ 20 mm in greatest dimension
T1mi	Tumor ≤ 1 mm in greatest dimension
T1a	Tumor > 1 mm but ≤ 5 mm in greatest dimension
T1b	Tumor > 5 mm but ≤ 10 mm in greatest dimension
T1c	Tumor > 10 mm but ≤ 20 mm in greatest dimension
T2	Tumor > 20 mm but ≤ 50 mm in greatest dimension
T3	Tumor > 50 mm in greatest dimension
T4	Tumor of any size with direct extension to the chest wall and/or to the skin (ulceration or skin nodules)
T4a	Extension to the chest wall, not including only pectoralis muscle adherence/invasion
T4b	Ulceration and/or ipsilateral satellite nodules and/or edema (including peau d’orange) of the skin, which do not meet the criteria for inflammatory carcinoma
T4c	Both T4a and T4b
T4d	Inflammatory carcinoma
Regional lymph nodes (N)
NX	Regional lymph nodes cannot be assessed (for example, previously removed)
N0	No regional lymph node metastases
N1	Metastases to movable ipsilateral level I, II axillary lymph node(s)
N2	Metastases in ipsilateral level I, II axillary lymph nodes that are clinically fixed or matted; or in clinically detected ipsilateral internal mammary nodes in the absence of clinically evident axillary lymph node metastases
	Metastases in ipsilateral level I, II axillary lymph nodes fixed to one another (matted) or to other structures
N2a	Metastases only in clinically detected ipsilateral internal mammary nodes and in the absence of clinically evident level I, II axillary lymph node metastases
N2b
N3	Metastases in ipsilateralinfraclavicular (level III axillary) lymph node(s) with or without level I, II axillary lymph node involvement; or in clinically detected ipsilateral internal mammary lymph node(s) with clinically evident level I, II axillary lymph node metastases; or metastases in ipsilateral supraclavicular lymph node(s) with or without axillary or internal mammary lymph node involvement
N3a	Metastases in ipsilateralinfraclavicular lymph node(s)
N3b	Metastases in ipsilateral internal mammary lymph node(s) and axillary lymph node(s)
N3c	Metastases in ipsilateral supraclavicular lymph node(s)
Distant metastases (M)
M0	No clinical or radiographic evidence of distant metastases
cM0(i +)	No clinical or radiographic evidence of distant metastases, but deposits of molecularly or microscopically detected tumor cells in circulating blood, bone marrow, or other nonregional nodal tissue that are no larger than 0.2 mm in a patient without symptoms or signs of metastases
M1	Distant detectable metastases as determined by classic clinical and radiographic means and/or histologically proven larger than 0.2 mm