The skin thickness overlying the breast normally measures between 0.5 to 2.0 mm. Skin thickening of the breast is associated with a number of benign and malignant conditions and results from either direct infiltration of the skin or from lymphatic congestion/obstruction. Breast parenchymal edema typically occurs in concert with skin thickening and manifest mammographically as trabecular thickening and an overall increased density of the breast.

Specific benign causes of breast skin thickening include mastitis, post irradiation change, lymphatic disruption following axillary node dissection, fat necrosis, interstitial hematoma, and systemic conditions (congestive heart failure, renal failure, and hypoalbunemia). Dermatologic conditions such as psoriasis and systemic sclerosis may also result in skin thickening. Malignant causes include inflammatory or locally advanced breast cancer, lymphatic obstruction secondary to metastatic disease to axillary lymph nodes, metastatic disease from a non-breast primary, and lymphoma.

Breast thickening as the result of lymphatic disruption can occur from the level of the dermal lymphatics to central drainage of the breast through the axilla and into the mediastinum As noted above, lymphatic obstruction at the nodal level can be the result of either post-surgical disruption of the lymphatics with axillary lymph node dissection or nodal metastatic disease. Axillary nodal dissection may be part of the surgical approach to both breast and non-breast malignancies (i.e. malignant melanoma).