Lymph drainage of the upper limb and mammary region to the axilla: anatomical study in stillborns.

Purpose: We studied the lymphatic drainage of the upper limb and mammary region directing to the axilla to investigate whether independent pathways can be observed or whether anastomoses and shared drainage occur between them. This analysis aimed to assess the safety of axillary reverse mapping (ARM) in breast cancer treatment and to understand the development of lymphedema after sentinel lymph node biopsy (SLNB) alone.

Methods: Seven unfixed stillborn fetuses were injected with a modified Gerota mass in the peri-areolar area, palm and dorsum of the hands, formalin fixed, and then submerged in 10% hydrogen peroxide solution. Microsurgical dissection was then performed on the subcutaneous cellular tissue of the upper limb, axillary region, and anterior thorax to expose the lymphatic vessels and lymph nodes.

Results: The dye injected into the upper limb reached either the lateral axillary group, known to be exclusively responsible for upper limb drainage, or the anterior group, which is typically related to breast drainage. There was great proximity among the pathways and lymph nodes. Communicating lymphatic vessels among these groups of lymph nodes were also found in all studied cases.

Discussion: Lymphedema remains a challenging morbidity in breast cancer treatment. ARM and SLNB aim to avoid unnecessary damage to the lymphatic drainage of the upper limb. However, our anatomical study suggests that ARM may have potential oncological risks because preserved lymph nodes may harbor malignant cells due their proximity, overlapping drainage pathways, and connecting lymph vessels among lymph nodes.