Bulbourethral Gland Cysts in Three Mice.

Diseases of bulbourethral glands have rarely been reported in mice. The present report describes bulbourethral gland cysts in three male mice: a.1yearold DBA/2J mouse (case 1), a 10monthold nude mouse (case 2), and a 4.5monthold chimeric mouse (case 3). Round to oval fluctuant nodules were observed on their dorsal perineum. The nodules in cases 1 and 2 were pale, pink to tan, soft, and glistening; in case 3, the mass was purple-red and soft. All nodules were located subcutaneously between the bulbospongiosus and ischiocavernous muscles, with a deep connection to the urethra. The nodules were 13 mm (case 1), 6 mm (case 2), and 8 mm (case 3) in diameter. The cut surface of the nodules was cystic; the lumina were filled with clear gelatinous or viscous (cases 1 and 2) or thin blood-tinged fluid (case 3). The nodules comprised irregular cysts and acini that were lined by a single layer of cuboidal, pyramidal to tall columnar epithelial cells with little stroma. Bulbourethral gland cysts should be included as differential diagnoses for perineal nodules or swellings in mice.