Lymph Drainage of the Mammary Glands in Female Cats

Abstract

The mammary gland is a common site of neoplasms in the female cat. All the malignant tumors metastasize to a lesser or a greater extent through the lymphatic system. However, the anatomical knowledge of this system is not sufficiently well known in cats to develop a reasoned model for the extirpation of these glands in case of malignant tumors. A study of the lymph drainage in 50 female cats was done by indirect injection in vivo of India ink inside the mammary parenchyma. After a waiting interval, mammary glands were extracted and the thoracic cavity opened. All the lymph nodes were examined after clearing. The success rate of the colorations of lymph nodes and lymph vessels was 91.8%. Out of the 100 observed mammary chains, the two intermediate mammary glands (T2, A1) may drain caudally to the superficial inguinal lymph center and/or cranially to the axillary lymph center. The T1 gland always drains exclusively cranially and A2 exclusively caudally. The two mammary glands (T1 and A1) often drain towards the sternal cranial lymph nodes, but 100% of the T2 drain towards it. This research assumes that the limit between the two directions of drainage can exist only between glands T2 and A1. The results obtained with the study of the 1st, 2nd, 3rd, and 4th mammary glands permit production of new and more complete data of functional significance that will eventually aid block dissection surgical technique in the removal of malignant tumors in cats. J. Morphol. 000: 000 – 000, 2005. © 2005 Wiley-Liss, Inc. to the inguinal region (Barone, 1996). Generally, the anterior pair of glands is affected and metastases frequently involve the regional lymph nodes and lungs (Hayden and Nielsen, 1971). Earliest surgical excision is the most effective therapy for any mammary tumor. In the cat, few surgical techniques are used in the treatment of mammary tumors (Hayes and Mooney, 1985). Surgical removal of all the glands on the affected side is a common method of treatment. Block dissection surgical techniques involve the removal of the affected mammary glands together with their lymphatic connections with other glands, the lymph nodes toward which these glands drain, and the other glands with which they are connected (Mann, 1984). The application of this technique is very limited in female cats due to the lack of sufficient data on the anatomy of the lymphatic system draining the glands. The few works, when available, are based on a very limited number of animals (Sugimura et al., 1956; Meier, 1989). For these reasons, we decided to investigate the lymphatic drainage and the lymphatic connections between mammary glands in cats, with the aim of developing a reasoned model for the extirpation of these glands in cases of malignant tumors.