The Veterinary Journal

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1 Available online at The Veterinary Journal 175 (2008) The Veterinary Journal The buccal lymph node (lymphonodus buccalis) in dogs: Occurrence, anatomical location, histological characteristics and clinical implications Christophe R. Casteleyn a, *, Maartje van der Steen a, Jan Declercq b, Paul Simoens a a Department of Morphology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium b Department of Small Animal Medicine and Clinical Biology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium Accepted 28 January 2007 Abstract Three dogs were presented for clinical examination with bilateral buccal nodules which were identified as enlarged buccal lymph nodes. As little is known about this pathology, 150 dogs were examined by anatomical dissection for the presence of buccal lymph nodes. They were found in 13 dogs, occurring bilaterally in six dogs and unilaterally in seven dogs. Two buccal lymph nodes were bilobulated and one was double. The lymph nodes were always located dorsal to the zygomatic muscle and rostral to the masseter muscle in the region where the superior labial vein drains into the facial vein. Histology demonstrated a large amount of intranodal adipose tissue scattered throughout the lymphoid tissue. The canine buccal lymph node should not be confused with the accessory parotid or ventral buccal salivary gland and is clinically important as it can enlarge due to tumour metastasis or inflammation of the buccal region. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Anatomy; Buccal nodule; Dog; Histology; Lymphatic system 1. Introduction A 7-month-old Afghan hound, a 3.5-month-old Newfoundland pup and an 8-year-old Shar pei were presented for evaluation of bilateral nodular lesions in the buccal region (Figs. 1a, 1b and 1c). The nodules, which were not painful in any of the dogs, ranged from 1 to 2 cm in diameter and were diagnosed as enlarged buccal lymph nodes. In the Afghan Hound, clinical examination revealed no other abnormalities and the buccal lymph nodes spontaneously regressed. The Newfoundland pup had a subcutaneous abscess in the right upper lip. The Shar pei suffered from generalized peripheral lymphadenopathy and subsequently showed nodular lesions in the ears, the anal region and the perivulvar fold. Histopathological examination of * Corresponding author. Tel.: ; fax: address: Christophe.Casteleyn@Ugent.be (C.R. Casteleyn). skin biopsy specimens revealed cutaneous non-epitheliotropic lymphoma. The anatomical features and possible pathology of buccal lymph nodes are poorly documented. Rumph et al. (1980) described a clinical case of a 4-month-old male Labrador Retriever presented with masses rostroventral to each eye. The masses were periodically swollen, but seemed not to induce any disease. Based on this clinical case, the authors systematically looked for similar masses and found them in 15/171 examined Greyhounds. After histology, they concluded that the masses were lymph nodes which they named the facial lymph node. Shelton and Forsythe (1979) performed a similar study and found the lymph node, which they called the buccal lymph node (lymphonodus buccalis), in 22/250 dogs of various breeds, ages and sex. Both the studies of Shelton and Forsythe (1979) and Rumph et al. (1980) have been briefly reviewed by Evans (1993). Adams (1986) illustrated in a textbook drawing /$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi: /j.tvjl

2 380 C.R. Casteleyn et al. / The Veterinary Journal 175 (2008) in the literature and because of its possible clinical implications, a screening was performed to determine its prevalence, exact anatomical location and histological characteristics. 2. Materials and methods Fig. 1a. Bilateral enlargement of buccal lymph nodes (arrows) in an Afghan hound due to unknown aetiology. The buccal regions of 150 dogs of various breeds, age and sex, euthanased for reasons other than this study, were examined macroscopically (Table 1). Photographs of each presumed buccal lymph node were taken using a digital camera (Canon EOS 300D) and samples for histological analysis were fixed in 3.5% buffered formaldehyde for 1 week followed by paraffin wax embedding using a histokinette (Shandon Citadel 1000, Thermo Electron). Tissue sections (8 lm thick) were made, mounted on slides, stained with haematoxylin (Hematoxylin C.I , Merck) and eosin (Eosine yellow C.I , VWR International) and examined with a motorized microscope (Olympus BX 61) linked to a digital camera (Olympus DP 50). Fig. 1b. A 4-month-old Newfoundland pup with enlarged buccal lymph nodes caused by abscessation of the right upper lip (arrow). Fig. 1c. Bilaterally enlarged buccal lymph nodes (arrows) in a Shar pei suffering from a cutaneous non-epitheliotropic lymphoma. an anonymous but apparently similar lymph node located rostral to the angle of confluence of the facial and the superior labial veins. The buccal lymph node has been described in various other species including humans, primates, rabbits, guinea pigs, rats and camels (Barone et al., 1950; Spira, 1962; Grassé, 1972; Grau, 1974; Barone, 1996). Since the presence of the canine buccal lymph node is rarely documented Table 1 Occurrence of the buccal lymph node in 150 dogs of various breeds Breed Number of dogs examined Unilateral presence of buccal lymph node American Staffordshire Terrier Basset Hound Beagle Belgian Malinois Belgian Tervuren Berner Sennen Boerboel Border Collie Bouvier des Flandres Boxer Bull Terrier Collie Dalmatian Doberman Pincher Dogue de Bordeaux English Bulldog Flat Coated Retriever German Pointer German Shepherd Dog Giant Schnauzer Golden Retriever Great Dane Groenendaler Irish Setter Jack Russell Terrier Keeshond Labrador Retriever Maltese Mongrel Napolitan Mastiff Newfoundland Pekingese Rottweiler Saint Bernard Shar pei Siberian Husky Standard Poodle Weimaraner Total Bilateral presence of buccal lymph node

3 C.R. Casteleyn et al. / The Veterinary Journal 175 (2008) For reference, samples were also taken from the mandibular and parotid lymph nodes and from the parotid, accessory parotid and ventral buccal salivary glands. 3. Results 3.1. Prevalence and macroscopic characteristics In 2/150 examined dogs, the buccal lymph nodes were enlarged causing a swelling which could be palpated through the skin. After dissection, the buccal lymph nodes were found in 13 dogs (i.e. 9% of all examined dogs). The lymph nodes were bilaterally present in six dogs and unilaterally in seven dogs, more specifically four times on the left side and three times on the right side of the head (Table 1). Two out of the total number of 19 observed buccal lymph nodes were bilobulated and one was double. The lymph nodes were always located dorsal to the zygomatic muscle and rostral to the masseter muscle in the region where the superior labial vein drains into the facial vein (Fig. 2). The buccal lymph node was located rostral to the facial vein in seven cases: once dorsal to the superior labial vein in the angle of confluence of the facial and superior labial veins, once medial to the superior labial vein (Fig. 3), four times directly ventral to the angle of confluence of the facial and superior labial veins (Fig. 4a), and once more caudal to the angle of confluence. In one case the lymph node was located medial to the facial vein where the superior labial vein joined the facial vein. In the other 11 cases, the lymph node was located caudodorsal to the facial vein: four times directly caudal to the angle of confluence of the facial and superior labial veins, and seven times ventral and distinctly caudal to the angle of confluence (Fig. 2). The distance between the angle of confluence and the buccal lymph node varied from 2 to 10 mm. The variable position of the observed canine buccal lymph nodes is illustrated in Fig. 4b. The size of the buccal lymph nodes was variable with the long rostrocaudal axis ranging from 5 to 24 mm, the short dorsoventral axis from 3 to 14 mm, and the thickness from 1 to 5 mm. Fig. 3. Bilobulated buccal lymph node (arrows) located medial to the superior labial vein. Notice the position of the buccal lymph node at the level of the fourth premolar (P4) in the right upper jaw of a German Shepherd Dog. Fig. 4a. Drawing of the canine head showing a buccal lymph node located directly ventral to the angle of confluence of the facial and superior labial veins. Some landmarks of the buccal area are additionally represented: ln. buccalis (1), lnn. mandibulares (2), ln. parotideus (3), gl. parotis (4), gl. parotis accessoria (5), gl. mandibularis (6), m. zygomaticus (7), m. masseter (8), m. buccinator (9), m. orbicularis oris (10), v. jugularis externa (11), v. maxillaris (12), v. facialis (13), v. labialis inferior (14), v. labialis superior (15), v. lateralis nasi (16). Fig. 2. Localisation of the buccal lymph node (arrow) in a Doberman Pincher in relation to the facial (1) and superior labial (2) veins and the zygomatic (3) and masseter (4) muscles. Fig. 4b. Compilation drawing of the canine head showing the variability of the buccal lymph nodes which are located nearby (black dots) or medial to (white dots) the facial or superior labial vein.

4 382 C.R. Casteleyn et al. / The Veterinary Journal 175 (2008) Histological characteristics The typical lymph node architecture was not always easily recognisable in histological sections of the canine buccal lymph nodes (Figs. 5a and 5b). However, all lymph nodes were encapsulated by connective tissue composed of collagen and fibroblasts with trabeculae radiating into the node. Smooth muscle cells, capillaries and adipose tissue could frequently be observed in the trabeculae. In 11 buccal lymph nodes, a cortical and medullary layer could be distinguished. The cortex was largely filled by diffuse lymphatic tissue and with primary and secondary lymph follicles. Subcapsular sinuses were detected at the periphery of the cortex, just underneath the capsule. The medulla was composed of medullary cords and sinuses. In all canine buccal lymph nodes, varying amounts of adipose cells were distributed throughout the lymphoid tissue. In contrast, the reference samples from the mandibular and parotid lymph nodes contained only few adipose cells which were mainly located in the trabeculae Reference samples Fig. 5a. Histological section of a canine buccal lymph node encapsulated by a capsule of dense connective tissue (C) sending trabeculae (T) into the lymph node. The lymph node is composed of primary (I) and secondary (II) lymph follicles. A limited amount of adipose tissue (A) and erythrocytes (E) are scattered throughout the lymphoid tissue (Haematoxylin-eosin staining). Fig. 5b. Histological section of a canine buccal lymph node containing large clusters of adipose tissue (A) and a very limited amount of lymphoid tissue (L). The lymph node is encapsulated by a capsule of connective tissue (C) sending trabeculae into the lymph node (T) (Haematoxylineosin staining). Both the parotid gland and the accessory parotid gland, which was usually present in close association to the parotid duct, were composed of serous glandular tissue. In contrast, the mandibular and buccal salivary glands consisted of sero-mucous acini. In one case, a presumed canine buccal lymph node was identified as a ventral buccal salivary gland by means of histology. Reference samples taken from mandibular and parotid lymph nodes revealed the typical architecture of a lymph node, consisting of a capsule and trabeculae, the cortex containing subcapsular sinuses and primary and secondary lymph follicles, and the medulla containing medullary cords and sinuses. 4. Discussion With regard to nomenclature, the lymph node in the buccal region has for many years been called ln. facialis in guinea pigs (Spira, 1962) and dogs (Rumph et al., 1980). On the other hand, authors such as Shelton and Forsythe (1979) use the term ln. buccalis. This nomenclature confusion has recently been resolved by the International Committee on Veterinary Gross Anatomical Nomenclature by officially recognizing the term ln. buccalis belonging to the Lymphocentrum mandibulare (Nomina Anatomica Veterinaria, 2005). The present study revealed that the buccal lymph node is only present in a minority of dogs. The observed prevalence of 9% is in accordance with the findings of Shelton and Forsythe (1979) and Rumph et al. (1980). Any conclusion about breed distribution should be made with reservations but our data suggest that the buccal lymph node is mainly present in larger purebred dogs as no buccal lymph node was found in small or medium breeds or in the 41 mongrels examined in this study. The buccal lymph node is not only inconsistently found in dogs, but also in guinea pigs (Barone et al., 1950), primates and camels (Spira, 1962; Grau, 1974). In contrast, it is always present in humans and rabbits (Barone et al., 1950; Spira, 1962; Grau, 1974; Barone, 1996). The canine buccal lymph node is always located rostral to the masseter muscle and lateral to the buccinator muscle, but its relation to the facial vein is variable. All canine buccal lymph nodes observed by Shelton and Forsythe (1979) and Rumph et al. (1980) were located directly dorsal, ventral or rostral to the angle of confluence of the facial and superior labial veins. In addition to both studies, we have also observed two buccal lymph nodes which were located medial to these veins. Because of its localisation, the buccal lymph node could be confused with the accessory parotid or ventral buccal salivary gland. However, the identity of any presumed buccal lymph node can easily be determined histologically. Few data are available concerning the drainage area of the canine buccal lymph node. Afferent lymph from facial structures, including the nose, upper lip and buccal region, drains into the buccal lymph nodes, and the efferent lymphatics discharge into the mandibular lymph nodes (Shelton and Forsythe, 1979). The drainage area of the canine buccal lymph node can be determined by injecting inert parti-

5 C.R. Casteleyn et al. / The Veterinary Journal 175 (2008) cles such as Chinese ink or Prussian blue (Barone, 1996) into the connective tissue of various head regions of living dogs. The particles will then be captured by macrophages which will enter the lymphatics and drain to the associated lymph nodes which will subsequently become stained. This experiment would require a large number of animals because of the low prevalence of the canine buccal lymph node. Our findings would suggest that a minimum of 10 dogs of preferably large and pure breeds would be needed. 5. Conclusion The canine buccal lymph node is clinically important as it can enlarge due to tumour metastasis or inflammation of the buccal region. In some diseased patients, however, the swelling may remain idiopathic. Although the buccal lymph node is only present in a minority of dogs, clinicians should be aware of its existence when dealing with nodular buccal swelling in practice. Acknowledgements The authors are grateful to L. De Bels, B. De Pauw, L. Standaert and P. Vervaet for excellent technical assistance. References Adams, D.R., Canine Anatomy. first ed. Iowa State University Press, Ames, pp Barone, R., Anatomie comparée des mammifères domestiques, Tome cinquième, Angiologie. Editions Vigot, Paris, pp , Barone, R., Bertrand, M., Desenclos, R., Recherches anatomiques sur les ganglions lymphatiques des petits rongeurs de laboratoire. Revue de Médecine Vétérinaire 101, Evans, H.E., Miller s Anatomy of the Dog. third ed. W.B. Saunders Company, Philadelphia, London, p Grassé, P.-P., Traité de Zoölogie, Tome XVI, fascicule IV. Masson Editeurs, Paris, pp Grau, H., Vergleichende Darstellung des Lymphgefäßsystems der Säugetiere. Verlag Paul Parey, Berlin und Hamburg, pp Nomina Anatomica Veterinaria, th ed., World Association of Veterinary Anatomists, Hamburg, Columbia, Ghent, Sapporo, p. 109, (accessed ). Rumph, P.F., Garrett, P.D., Gray, B.W., Facial lymph nodes in dogs. Journal of the American Veterinary Medical Association 176, Shelton, M.E., Forsythe, W.B., Buccal lymph node in the dog. American Journal of Veterinary Research 40, Spira, A., Die Lymphknotengruppen (Lymphocentra) bei den Säugern ein Homologisierungsversuch. Anatomischer Anzeiger 111,