Accessory Axillary Lymph Nodes

The accessory axillary lymph node (Figures 13: 4; 16: e’) is a relatively small, infrequent lymph node. It was found in only 10 of 43 cases: 6 times on both sides, 3 times only on the right, and 1 time only on the left. The lymph node was always found alone. It is located 4 to 8 cm dorsal to the olecranon, just dorsal to the M. pectoralis profundus and just ventral to the M. latissimus dorsi, close to the angle formed between them at the caudal border of the muscles of the shoulder and brachium on the 3rd and 4th ribs, most often in the 3rd intercostal space.

The lymph node is covered only by the skin and the M. cutaneous trunci (Figure 13: m), although in rare cases, it is located on the medial side of the M. latissimus dorsi.

Afferent drainage

The accessory axillary lymph node drains the lymph vessels of the skin on the lateral and ventral thoracic wall and on the caudal aspect of the lateral and medial side of the humerus and olecranon, the lymph vessels from the M. cutaneous trunci, the M. pectoralis profundus, and from the mammary gland. If the accessory axillary lymph node is absent, the afferent vessels from the aforementioned structures drain directly to the axillary lymph node, providing evidence that the accessory axillary lymph node is associated with the axillary lymph node. This is in contrast to Merzdorf [24], who named this lymph node the cubital lymph node. Based on its location, the accessory axillary lymph node in dogs may be compared to the infraspinous lymph node in cattle, although the lymph node in cattle has a completely different drainage region than the lymph node in dogs.

Efferent drainage

The efferent vessels from the accessory axillary lymph node merge to form 2 to 3 vessels (Figure 16: e, e’), which form anastomoses among themselves, and drain into the axillary lymph node.

Clinical Notes

Ventral radiograph of the thoracic region of a dog showing the location of the axillary and accessory axillary lymph nodes using contrast.
Contrast uptake in the left axillary (white arrowhead) and accessory axillary (black arrowhead) lymph nodes on a ventrodorsal radiograph of the cranial thorax in a healthy dog. Image credit: Dr. Monique Mayer, Western College of Veterinary Medicine, University of Saskatchewan (used under CC BY-NC).


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The Lymphatic System of the Dog Copyright © 2021 by Hermann Baum is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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