Mixed Thymoma in a Young Cynomolgus Monkey (Macaca fascicularis)

A mass with a diameter of 1.5 cm was found in the thymus of a 4-year and 3-month-old male cynomolgus monkey. Microscopically, the mass consisted of two different patterns of proliferation, dense or fascicular proliferation of elongated spindle cells in a sporadic storiform pattern and dense proliferation of thymic cortex-like lymphoid cells in which the multifocal pale nests resembling the thymic medulla were distributed. In these pale nests, large dendriform cells sometimes forming Hassall’s corpuscles were present. The proliferating spindle cells were positive for cytokeratin. The lymphoid cells in the mass were positive for CD3. We concluded that the mass consisted of the neoplastic thymic epithelium with thymocytes proliferation containing medullary differentiation. The mass was diagnosed as a mixed thymoma according to the WHO classification of thymomas in humans. Mixed thymoma is characterized as a mixture of two types of proliferative lesions, spindle-shaped epithelial proliferation and a lymphocyte predominant lesion with or without medullary differentiation. To the best of our knowledge, this is the first report concerning thymoma in monkeys

Histopathology of Incidental Findings in Cynomolgus Monkeys (Macaca Fascicularis) Used in Toxicity Studies

The purpose of our publication is to widely communicate pictures of spontaneous findings occurring in cynomolgus monkeys. Focal lymphoplasmacytic infiltration is commonly seen in the general organs. The frequency and severity of these lesions may be influenced by the administration of drugs with an effect on the immune system. Lymphoplasmacytic infiltration in the lamina propria of the stomach is also frequently seen in cynomolgus monkeys, and it is caused mainly by a Helicobacter pylori infection. Various degrees of brown pigments are observed in various organs, and it is possible to distinguish the material of the pigments by its morphological features and site. A focal/segmental glomerular lesion is occasionally seen in a section of the kidney, and the minimal lesion has no influence on the urinalysis. We showed the common glomerular lesions in HE-stained sections, as well as in PAM- or PAS-stained sections, for understanding the details. Young and pubertal monkeys are usually used in toxicity studies; therefore, understanding various maturation stages of the genital system is important. In particular, the female genital system needs to be understood in the morphology, because their cyclic changes are different from other laboratory animals. Thus, we present the normal features of the cyclic changes of the female genital organs. Furthermore, we provide more information on spontaneous findings in cynomolgus monkeys for exact diagnoses in toxicity studies

The connections of the inferior colliculus and the organization of the brainstem auditory system in the greater horseshoe bat (Rhinolophus ferrumequinum)

The connections of the inferior colliculus, the mammalian midbrain auditory center, were determined in the greater horseshoe bat (Rhinolophus ferrumequinum), using the horseradish peroxidase method. In order to localize the auditory centers of this bat, brains were investigated with the aid of cell and fiber-stained material. The results show that most auditory centers are highly developed in this echolocating bat. However, the organization of the central auditory system does not generally differ from the mammalian scheme. This holds also for the organization of the superior olivary complex where a well-developed medial superior olivary nucleus was found. In addition to the ventral and dorsal nuclei of the lateral lemniscus a third well-developed nucleus has been defined which projects ipsilaterally to the inferior colliculus and which was called the intermediate nucleus of the lateral leminiscus. All nuclei of the central auditory pathway project ipsi-, contra-, or bilaterally to the central nucleus of the inferior colliculus with the exception of the medial nucleus of the trapezoid body and the medial geniculate body. The tonotopic organization of these projections and their possible functions are discussed in context with neurophysiological investigations

Malignant Mesothelioma in the Thoracic Cavity of a Crj:CD(SD) Rat Characterized by Round Hyalinous Stroma

Spontaneous malignant mesothelioma was found in a 104-week-old male Crj:CD(SD) rat. The tumor was scattered on the surface of the lung, heart, mediastinal pleura and thoracic wall and metastasized to the alveolar septa. Histopathologically, small flattened or cuboidal tumor cells proliferated with stroma, formed almost normal papillary structures and reacted positively to colloidal iron stain and immunohistochemical staining for mesothelin. Round hyalinous stromata were pronounced, which is a characteristic feature, and the possible reason for this is as follows; at first, a small amount of collagen fibers was formed in the center of the clusters of several tumor cells, and then the cell clusters expanded like balloons with an increase in the collagen fibers