Cysts of branchial arch origin in the thymus of the Beagle

Abstract

Examination of thymus glands from Beagles used in routine toxicological experiments revealed an age‐related increase in the incidence and size of cysts of branchial origin in the groups: 28–30 months, 16–18 months, 10–12 months, 6–8 months. The cysts varied in size and in the distribution of the cell types constituting the epithelium. Histochemical examination of cyst contents revealed mucosubstances that were considered similar to those of normal respiratory mucins in man. SUMMARY The incidence of small cysts of branchial arch origin in the thymus of beagles was seen to increase with age. The increase is considered to be greater than that attributable to the regression of surrounding thymic tissue alone. Reference is made to a clinical case in which cystic distension of the thymus was present. Résumé. L'examen de thymus de chiens Beagle utilisés en expériences courantes de toxicologie a fait ressortir un accroissement proportionnel à l'âge dans la fréquence et la dimension des kystes d'origine branchiale, dans les groups de 28–30 mois, 16–18 mois, 10–12 mois, 6–8 mois. Les kystes présentaient des variations de grosseur, ainsi que dans la répartition des cellules type constituant l'épithélium. L'analyse histochimique du contenu des kystes a révélé des mucosubstances considtétés similaires à celles des mucosités normales du système respiratoire de l'homme. Zusammenfassung. Prüfung der Thymusdrüsen von Hirschhunden in normalen toxikologischen Versuchen zeigte mit dem Alter zusammenhängende Steigerung im Auftreten und in der Größe von Zysten mit Kiemenurspxung in den Gruppen 28–30 Monate, 16–18 Monate, 10–12 Monate, und 6–8 Monate. In der Größe der Zysten und in der Verteilung der das Epithelgewebe bildenden Zellentypen waren Schwankungen festzustellen. Histochemische Untersuchung der Zysteninhalte ergab Schleimsubstanzen, die ähnlich den normalen Mucinen in den Atmungswegen des Menschen erschienen.

Transformation of a thymic branchial cyst to a carcinoma with pulmonary metastasis in a dog

“…There are few veterinary reports concerning thymic branchial cysts (Newman 1971, Liu and others 1983, Day 1997). To the authors’ knowledge, neoplastic transformation and metastasis of a thymic branchial cyst have not been reported in the veterinary or human being literature.…”

Thymic structure and function in aging dogs

“…If these structures were true branchial remnants we should ea^ect the incidence of cysts to be equal in the young and the aged and the Aequency of occurrence to be much lower than that found in this and other studies (Oksanen, 1968;Watney, 1882;White, 1942;Newman, 1971).…”

“…Ihe hi^ incidence of thymic cysts in adult dogs, and their paucity in normal young dogs, argues against the interpretation of these structures as branchial remnants (Qksanen, 1968;Watney, 1882;White, 1942;Newman, 1971;Bodey et al, 1987). Other authors have interpreted thymic <^sts as derivatives of degenerating thymic corpuscles (Watney, 1882;Hammar, 1921 As noted Toy Qksanen (1968), White (1942), and Newman (1971) the incidence of thymic cysts ag^pears to be related to increasing age.…”

“…With hiatochfitnical techniques, Oksanen (1968) and Newman (1971) found the lumined contents of thymic cysts to ccntedn neutral and acidic mucins, and complex sulphated 'mucosubstanoes'; the cyst epithelia stained positively for six different enzymes (Oksanen, 1968).…”

“…Ihere is a positive correlation between aging and cyst incidence in the dog (White, 1942;Bargmann, 1943;Newman, 1971). Oksanen (1968) found the incidence of thymic cysts to be only partly dependent on age in dogs;…”