19 research outputs found
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
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