Assessment of SOX10 expression in 437 canine neoplasms of different embryologic origins.

Several members of the SRY-related HMG-box (SOX) protein family are implicated in tumorigenesis, metastasis, and regulation of the tumor microenvironment. SOX10, which is involved in neural crest cell migration and differentiation, has long been recognized a sensitive and specific immunohistochemical (IHC) marker in the diagnosis of melanoma in humans. However, expression of SOX10 in other tumor types has infrequently been evaluated in humans until recently and has not been thoroughly investigated in the dog. Our aim was to characterize the expression of SOX10 in canine neoplasms to objectively assess its value as a diagnostic IHC marker. Immunohistochemistry for SOX10 was performed on 437 archived, formalin-fixed paraffin-embedded tissues from representative canine neoplasms of ectodermal (15 tumor types), mesodermal (13 tumor types), endodermal (8 tumor types), and mixed/unknown (7 tumor types) embryologic origin. Oral and cutaneous tumors of melanocytic origin were used as positive controls. Intense SOX10 immunolabeling was observed in most tumors of ectodermal origin, including consistent expression in mammary carcinomas, and gliomas. Embryonal and hair follicle neoplasms inconsistently exhibited strong nuclear immunolabeling. Oral fibrosarcomas and undifferentiated oral sarcomas both inconsistently exhibited moderate to strong nuclear immunolabeling. Neoplasms of mesodermal and endodermal origin lacked immunolabeling. Salivary carcinomas, representing an unknown/mixed embryologic origin, were strongly labeled. SOX10 expression is not limited to melanomas, but is expressed by canine tumors of diverse tissues and embryologic derivation. Importantly, expression of SOX10 by a subset of oral sarcomas impairs its value as a marker for spindle cell oral melanomas.

Spontaneous Pituitary Neoplasm in Two Female Geriatric Southern Giant Pouched Rats (Cricetomys ansorgei).

Southern giant pouched rats (Cricetomys ansorgei) are a small muroid species native to the sub-Saharan Africa. Their exceptionally developed olfactory system, trainability, and relatively small size makes them useful working animals for various applications in humanitarian work. At our institution, a breeding colony of Southern giant pouched rats is maintained to study their physiology and utility as scent detectors. This case report describes the occurrence of spontaneous pituitary neoplasms with distinct clinical presentations in 2 geriatric (approximately 7.5 y old) wild-caught female Southern giant pouched rats. The first pouched rat displayed vestibular deficits, including left-sided head tilt, ataxia, disorientation, and circling. MRI revealed a large, focal heterogeneous mass arising from the pituitary fossa. The second pouched rat presented with polyuria, polydipsia, and hyperglycemia but no neurologic signs. Examination after euthanasia revealed a prolactin (PRL)-expressing pituitary carcinoma and adenoma in the first and second pouched rat, respectively, associated with mammary hyperplasia in both animals. This is the first report of spontaneous PRL-producing pituitary tumors in Southern giant pouched rats.