Peau d’orange: lymphatic obstruction in breast cancer

Peau d’orange is French for “orange peel”. It is thickened, pitted breast skin, and it can appear over a breast cancer when the lymphatic drainage of the skin is obstructed.

Lymphatic vessels are thin channels that carry excess tissue fluid away from the skin and breast. A tumour can block them by compressing them (pressing on them from outside) or by invading their walls (growing into them). The ones in the skin lie in the dermis, the deeper layer of the skin, and are called dermal lymphatics.

Once the vessels are blocked, the fluid has nowhere to go. It collects in the skin as oedema (swelling caused by excess tissue fluid), held in the interstitial space (the tissue space between cells), and the skin becomes thickened.

The suspensory ligaments of the breast (strands of fibrous tissue that anchor the breast skin) tether the skin at their attachments, so the swollen skin bulges in between and looks dimpled, like the peel of an orange.

It is seen in inflammatory breast cancer (a cancer that causes rapid-onset redness, swelling and skin thickening) and in some very advanced breast cancers. It needs proper assessment. A skin biopsy can show cancer cells in dermal lymphatic vessels, although they are found in some but not all areas of affected skin, so the sign points to a drainage problem rather than to a particular tumour type. The same appearance can follow axillary lymph node clearance (clearing out the lymph nodes in the armpit), because the cause is then poor lymphatic drainage rather than the cancer cells themselves.