Spontaneous squamous cell carcinomas in 13 baboons, a first report in a spider monkey, and a review of the non-human primate literature

Lingual neoplasia in nonhuman primates: Description of five cases and a literature review

BACKGROUND

Documentation of lingual tumors is scarce in nonhuman primates.

METHODS

Through a multi-institutional retrospective study we compile cases of primary and metastatic neoplasia in non-human primates.

RESULTS

We describe five cases of lingual neoplasia. Three cases are primary lingual tumors: chondro-osteoblastic lipoma in a howler monkey, squamous cell carcinoma, and fibroma in two baboons. We describe two cases of metastatic lymphoma in the tongue in rhesus macaques. A literature review of published lingual neoplasia in nonhuman primates is included in this manuscript.

CONCLUSION

Lingual neoplasia is seldom reported in non-human primates.

Oral cavity squamous cell carcinomas in zoo-managed Goeldi's monkeys (Callimico goeldii)

BACKGROUND

Oral cavity squamous cell carcinomas (OCSCCs) are relatively common in multiple non-human primate species but are poorly documented in Goeldi's monkeys.

METHODS

Four Goeldi's monkeys with OCSCC, from three zoological collections, underwent necropsy with cytology, histopathology, immunohistochemistry, and pan-herpesvirus PCR analysis.

RESULTS

All animals were euthanised and exhibited poor-to-emaciated body condition. Three OCSCCs arose from the maxillary oral mucosa and a single OCSCC was primarily mandibular, with bone invasion evident in three cases. Histologically, one OCSCC in situ was diagnosed, whilst the rest were typically invasive OCSCCs. Neoplastic cells were immunopositive for pancytokeratin and E-cadherin. All examined cases were negative for regional lymph node (RLN) and/or distant metastases, cyclooxygenase-2 (COX-2) immunoexpression, and panherpesvirus PCR expression.

CONCLUSIONS

OCSCCs in Goeldi's monkeys may be deeply invasive, but not readily metastatic. No herpesvirus-association or COX-2 expression was evident; the latter suggesting that NSAIDs are unlikely to be a viable chemotherapeutic treatment.

Gastrointestinal tract pathology of the owl monkey (Aotus spp.)

Owl monkeys are small nocturnal new world primates in the genus Aotus that are most used in biomedical research for malaria. Cardiomyopathy and nephropathy are well-described common diseases contributing to their morbidity and mortality; less is known about lesions affecting the gastrointestinal tract. Records from a 14-year period (2008-2022) at the Keeling Center for Comparative Medicine and Research were queried to identify instances of spontaneous gastrointestinal disease that directly contributed to the cause of death from the 235 adult owl monkeys submitted for necropsy. Of the 235, 10.6% (25/235) had gastrointestinal disease listed as a significant factor that contributed to morbidity and mortality. Diagnoses included candidiasis (3/25), gastric bloat (4/25), and intestinal incarceration and ischemia secondary (11/25), which included intussusception (4/25), mesenteric rent (3/25), strangulating lipoma (2/25), intestinal torsion (1/25), and an inguinal hernia (1/25). Intestinal adenocarcinomas affecting the jejunum (4/25) were the most common neoplasia diagnosis. Oral squamous cell carcinoma (1/25) and intestinal lymphoma (2/25) were also diagnosed. This report provides evidence of spontaneous lesions in the species that contribute to morbidity and mortality.

Causes of death in neotropical primates in Rio Grande do Sul State, Southern Brazil

BACKGROUND

Anthropogenic disturbances are the main threats to nonhuman primates conservation, and infectious diseases may also play a key role in primate population decline. This study aimed to determine the main causes of death in neotropical primates.

METHODS

A retrospective study of post-mortem examinations was conducted on 146 neotropical primates between January 2000 and December 2018.

RESULTS

Conclusive diagnoses were obtained in 68.5% of the cases, of which 59 corresponded to non-infectious causes and 41 to infectious diseases. Trauma was the main cause of death (54/100), with anthropogenic stressors caused by blunt force trauma injuries (collision with vehicles) and puncture wound injuries associated with interspecific aggression (dog predation) were the most common factors. Other causes of death included bacterial diseases (27%), followed by parasitic diseases (12%), neoplasms (2%), and viral diseases (2%).

CONCLUSIONS

Free-ranging primates were mostly affected by non-infectious causes, while captive primates were by infectious conditions.

Research Relevant Conditions and Pathology in Nonhuman Primates

Biomedical research involving animal models continues to provide important insights into disease pathogenesis and treatment of diseases that impact human health. In particular, nonhuman primates (NHPs) have been used extensively in translational research due to their phylogenetic proximity to humans and similarities to disease pathogenesis and treatment responses as assessed in clinical trials. Microscopic changes in tissues remain a significant endpoint in studies involving these models. Spontaneous, expected (ie, incidental or background) histopathologic changes are commonly encountered and influenced by species, genetic variations, age, and geographical origin of animals, including exposure to infectious or parasitic agents. Often, the background findings confound study-related changes, because numbers of NHPs used in research are limited by animal welfare and other considerations. Moreover, background findings in NHPs can be exacerbated by experimental conditions such as treatment with xenobiotics (eg, infectious morphological changes related to immunosuppressive therapy). This review and summary of research-relevant conditions and pathology in rhesus and cynomolgus macaques, baboons, African green monkeys, common marmosets, tamarins, and squirrel and owl monkeys aims to improve the interpretation and validity of NHP studies.

Urogenital Lesions in Nonhuman Primates at 2 National Primate Research Centers

Given their genetic and anatomic similarities to humans, nonhuman primates (NHPs) may serve as animal models for urogenital diseases of humans. The purpose of this study was to examine the frequency of spontaneous urogenital lesions occurring over a 30-year period at the Yerkes and Southwest National Primate Research Centers and to compare and contrast lesions occurring in Old World versus New World primates. Lesions occurring in the chimpanzee (Pan troglodytes), baboon (Papio spp.), rhesus macaque (Macaca mulatta), cynomolgus macaque (Macaca fascicularis), pig-tailed macaque (Macaca nemestrina), sooty mangabey (Cercocebus atys), common marmoset (Callithrix jacchus), cotton-top tamarin (Sanguinus oedipus), and squirrel monkey (Saimiri sciureus) are discussed. The most common lesions of the kidney were medullary amyloidosis, renal cysts, renal tubular degeneration, glomerulonephritis or glomerulopathy, nephritis, nephrocalcinosis, pyelonephritis, and hydronephrosis. Specific causes of renal tubular disease included pigmentary nephrosis and tubular lipidosis. Renal tumors, including renal adenoma and carcinoma, lymphoma, and nephroblastoma, were infrequent diagnoses in all species. Endometriosis was the most frequently diagnosed lesion of the female genital tract. Of the animals examined in this study, it was most frequent in Old World primates. Leiomyoma was the most common uterine tumor. Granulosa cell tumor was the most frequently observed neoplasm of the ovaries, followed by teratoma. Of animals included in the study, most ovarian tumors occurred in baboons. Neoplasms of the male reproductive tract included interstitial cell tumor, seminoma, penile squamous cell carcinoma, penile papilloma, and histiocytoma. In New World monkeys, renal lesions were reported more frequently than genital lesions.

The occurrence of cancer in vertebrates: a mini review

Neoplasia is a multilevel condition caused by irregularities over the genome, which can lead to a fatal result. To fully understand this phenomenon, an evolutionary challenge has risen during the last decades, away from human limits, driving the scientific quest into the wild life. The study of wild vertebrate populations in their natural habitats has shown that cancer is rather prominent. Thus, the diversity of vertebrates reported with some form of neoplasia is quite scattered through a variety of habitats. However, some species constitute exceptions by exhibiting cancer-protective features, driven by certain loci in their DNA. It is obvious that from an evolutionary standpoint, the incidence of cancer in different taxa is nowadays studied by seeking for patterns and their roots. The main purpose of the evolutionary approach is no other than to answer a fundamental question: Could cancer be ultimately regarded as another evolutionary force conducive to the formation or shaping-up of species?

Gingival histoplasmosis: An atypical presentation of African histoplasmosis in three baboons (Papio spp)

Gingival lesions as the sole manifestation of African histoplasmosis (Histoplasma capsulatum var. duboisii) have never been reported in baboons. Grossly, lesions can be indistinguishable from bacterial ulcerative gingivitis or gingival hyperplasia. Clinical outcomes of primary gingival histoplasmosis in baboons are unknown and may complicate colony management decisions.

Salivary gland neoplasms in non-human primates: A case series and brief literature review

BACKGROUND

Salivary gland neoplasms are rare in non-human primates.

METHODS

Thirty-five years of pathology records were reviewed at the Southwest (SNPRC) and Yerkes (YNPRC) National Primate Research Centers. An in-depth literature search for salivary gland neoplasms in non-human primates was performed.

RESULTS

Seventeen salivary gland neoplasms (nine from SNPRC and YNPRC, eight from published literature) were identified. There were seven malignant, nine benign, and one of undetermined behavior identified in eight rhesus macaques, six baboons, a chimpanzee, a bonnet macaque, and a moustached tamarin. Parotid gland was the most frequent origin (n = 7), followed by mandibular (n = 4) or minor salivary glands (n = 2). Two animals with salivary gland adenoma had a history of prior radiation exposure.

CONCLUSIONS

Parotid glands are the most common origin for salivary gland neoplasms. Salivary gland neoplasms should be considered in the differential diagnoses of head and neck masses in non-human primates.

Multicentric cutaneous keratoacanthomas in a free-living marmoset (Callithrix sp.)

Cutaneous neoplasia is common in non-human primates. We describe the gross and microscopic features of multicentric cutaneous keratoacanthomas in a free-living marmoset (Callithrix sp.). Immunohistochemistry for human papillomavirus and herpes simplex virus type I and simplex virus type II was negative. Keratoacanthomas should be included in the differential diagnosis for cutaneous masses in non-human primates.

ORONASAL SQUAMOUS CELL CARCINOMAS IN FRANÇOIS' LANGURS (TRACHYPITHECUS FRANCOISI)

Squamous cell carcinomas (SCCs) are common oronasal tumors in nonhuman primates. In this study, 11 cases of oronasal SCC in François' langurs ( Trachypithecus francoisi ) are described. Five initial cases were discovered on review of the North American François' langur studbook, with a potential familial pattern observed. The studbook was used to identify related individuals, and records were requested for review. Six additional cases were documented, and samples from all cases were submitted for microscopic review, as well as polymerase chain reaction (PCR), immunohistochemistry (IHC), and in situ hybridization (ISH), for generic papillomaviruses and PCR for herpesviruses because either virus may cause SCC in humans and other nonhuman primates. Affected langurs commonly presented with facial swelling or ocular discharge but frequently did not have clinical signs, and carcinomas were diagnosed during routine examinations. Carcinomas were located in the oral or nasal cavities affecting the oral mucosa, tongue, hard palate, or oropharynx. Histologically, SCCs comprised anastomosing cords and nests of neoplastic epithelial cells that differentiated synchronously and asynchronously from peripheral basal type cells to central squamous-type cells and were occasionally oriented around accumulations of necrotic cell debris. Nuclear pleomorphism, anisokaryosis, prominent nucleoli, occasional mitoses, and a scirrhous response were common features. All animals tested negative for both viruses, except two langurs that were positive for generic papillomavirus by PCR, but no papillomavirus was detected by either IHC or ISH. In most cases, affected animals died within 5 mo of diagnosis.

On the apparent rarity of epithelial cancers in captive chimpanzees

Malignant neoplasms arising from epithelial cells are called carcinomas. Such cancers are diagnosed in about one in three humans in 'developed' countries, with the most common sites affected being lung, breast, prostate, colon, ovary and pancreas. By contrast, carcinomas are said to be rare in captive chimpanzees, which share more than 99% protein sequence homology with humans (and possibly in other related 'great apes'-bonobos, gorillas and orangutans). Simple ascertainment bias is an unlikely explanation, as these nonhuman hominids are recipients of excellent veterinary care in research facilities and zoos, and are typically subjected to necropsies when they die. In keeping with this notion, benign tumours and cancers that are less common in humans are well documented in this population. In this brief overview, we discuss other possible explanations for the reported rarity of carcinomas in our closest evolutionary cousins, including inadequacy of numbers surveyed, differences in life expectancy, diet, genetic susceptibility, immune responses or their microbiomes, and other potential environmental factors. We conclude that while relative carcinoma risk is a likely difference between humans and chimpanzees (and possibly other 'great apes'), a more systematic survey of available data is required for validation of this claim.

Malignant Neoplasia of the Sex Skin in 2 Chimpanzees (Pan troglodytes)

This report describes 2 cases of spontaneous malignant neoplasia within the sex skin of aged female chimpanzees. In both cases, the initial presentation resembled nonhealing traumatic wounds to the sex skin, with different degrees of infection, ulceration, and tissue necrosis. Histopathology of the lesions confirmed the diagnosis of squamous cell carcinoma in one case and of adenocarcinoma with metastasis in the other. Advanced age and previous trauma likely contributed to the development of the neoplasias in both cases; long-term sun exposure may also have contributed to the development of the squamous cell carcinoma. To our knowledge, these 2 cases represent the first reports of sex skin neoplasia in chimpanzees.

Oral squamous cell carcinoma in a pigtailed macaque (Macaca nemestrina)

An adult, gravid, female pigtailed macaque (Macaca nemestrina) presented for facial swelling centered on the left mandible that was approximately 5 cm wide. Differential diagnoses included infectious, inflammatory, and neoplastic origins. Definitive antemortem diagnosis was not possible, and the macaque's condition worsened despite supportive care. Necropsy findings included a mandibular mass that was locally invasive and expansile, encompassing approximately 80% of the left mandibular bone. The mass replaced portions of the soft palate, hard palate, sinuses, ear canal, and the caudal-rostral calvarium and masseter muscle. Histologically, the mass was a neoplasm that was poorly circumscribed, unencapsulated, and infiltrative invading regional bone and soft tissue. The mass consisted of polygonal squamous epithelial cells with intercellular bridging that breached the epithelial basement membrane and formed invasive nests, cords, and trabeculae. The mitotic rate averaged 3 per 400× field of view, with occasional bizarre mitotic figures. Epithelial cells often exhibited dyskeratosis, and the nests often contained compact lamellated keratin (keratin pearls). The neoplasm was positive via immunohistochemistry for pancytokeratin, variably positive for S100, and negative for vimentin, smooth muscle actin, and desmin. The gross, histologic, and immunohistochemical findings were consistent with an aggressive oral squamous cell carcinoma. The neoplasm was negative via PCR for papilloma virus. In general, neoplasia in macaques is rare. Although squamous cell carcinomas are one of the most common oral neoplasia in many species, to our knowledge this case represents the first reported oral squamous cell carcinoma in a pigtailed macaque.

Mortality in captive baboons (Papio spp.): a-23-year study

BACKGROUND

We report the causes of mortality for 4350 captive baboons that died or were euthanized due to natural causes during a 23 year period at the Southwest National Primate Research Center.

METHODS

Necropsy records were retrieved and reviewed to determine a primary cause of death or indication for euthanasia. Data was evaluated for morphological diagnosis, organ system, and etiology.

RESULTS

The 20 most common morphologic diagnoses accounted for 76% of the cases, including stillborn (10.8%); colitis (8.6%); hemorrhage (8.4%); ulcer (5.2%); seizures (4.7%); pneumonia (4.2%); inanition (4.1%); dermatitis (3.8%); spondylosis (3.3%); and amyloidosis (3.0%). The digestive system was most frequently involved (21.3%), followed by the urogenital (20.3%), cardiovascular (12.2%), and multisystem disease (10.3%). An etiology was not identified in approximately one-third of cases. The most common etiologies were trauma (14.8%), degenerative (9.5%), viral (8.7%), and neoplastic/proliferative (7.0%).

CONCLUSION

This information should be useful for individuals working with baboons.

Spontaneous and experimental malignancies in non-human primates

Contrary to earlier established opinion that tumors in monkeys are found rarely, now the large material confirms that monkey tumors are frequent phenomenon. Tumor incidence clearly increases with age. Frequencies of benign and malignant tumors of various locations and histogenesis are slightly different. Tumors of hematopoietic system are the most frequent. Sporadic cases and enzootic outbreaks of lymphomas are described for different kinds of monkeys, including apes, and probably are caused by viruses. Two viruses were isolated by us from sick monkeys - the retrovirus C-type STLV-1 and the herpes virus papio HVP. Inoculation of virus cultures into monkeys and rabbits induces neoplasms. Monkey neoplasms can be induced by exposure to various chemical agents, and by oncogenic and non-oncogenic viruses. There is no strict species specificity of tumor viruses. The role of polyoma viruses in neoplasms etiology is discussed.

Meeting report: Spontaneous lesions and diseases in wild, captive-bred, and zoo-housed nonhuman primates and in nonhuman primate species used in drug safety studies

The combination of loss of habitat, human population encroachment, and increased demand of select nonhuman primates for biomedical research has significantly affected populations. There remains a need for knowledge and expertise in understanding background findings as related to the age, source, strain, and disease status of nonhuman primates. In particular, for safety/biomedical studies, a broader understanding and documentation of lesions would help clarify background from drug-related findings. A workshop and a minisymposium on spontaneous lesions and diseases in nonhuman primates were sponsored by the concurrent Annual Meetings of the American College of Veterinary Pathologists and the American Society for Veterinary Clinical Pathology held December 3-4, 2011, in Nashville, Tennessee. The first session had presentations from Drs Lowenstine and Montali, pathologists with extensive experience in wild and zoo populations of nonhuman primates, which was followed by presentations of 20 unique case reports of rare or newly observed spontaneous lesions in nonhuman primates (see online files for access to digital whole-slide images corresponding to each case report at http://www.scanscope.com/ACVP%20Slide%20Seminars/2011/Primate%20Pathology/view.apml). The minisymposium was composed of 5 nonhuman-primate researchers (Drs Bradley, Cline, Sasseville, Miller, Hutto) who concentrated on background and spontaneous lesions in nonhuman primates used in drug safety studies. Cynomolgus and rhesus macaques were emphasized, with some material presented on common marmosets. Congenital, acquired, inflammatory, and neoplastic changes were highlighed with a focus on clinical, macroscopic, and histopathologic findings that could confound the interpretation of drug safety studies.

Novel genital alphapapillomaviruses in baboons (Papio hamadryas anubis) with cervical dysplasia

Genital Alphapapillomavirus (αPV) infections are one of the most common sexually transmitted human infections worldwide. Women infected with the highly oncogenic genital human papillomavirus (HPV) types 16 and 18 are at high risk for development of cervical cancer. Related oncogenic αPVs exist in rhesus and cynomolgus macaques. Here the authors identified 3 novel genital αPV types (PhPV1, PhPV2, PhPV3) by PCR in cervical samples from 6 of 15 (40%) wild-caught female Kenyan olive baboons (Papio hamadryas anubis). Eleven baboons had koilocytes in the cervix and vagina. Three baboons had dysplastic proliferative changes consistent with cervical squamous intraepithelial neoplasia (CIN). In 2 baboons with PCR-confirmed PhPV1, 1 had moderate (CIN2, n = 1) and 1 had low-grade (CIN1, n = 1) dysplasia. In 2 baboons with PCR-confirmed PhPV2, 1 had low-grade (CIN1, n = 1) dysplasia and the other had only koilocytes. Two baboons with PCR-confirmed PhPV3 had koilocytes only. PhPV1 and PhPV2 were closely related to oncogenic macaque and human αPVs. These findings suggest that αPV-infected baboons may be useful animal models for the pathogenesis, treatment, and prophylaxis of genital αPV neoplasia. Additionally, this discovery suggests that genital αPVs with oncogenic potential may infect a wider spectrum of non-human primate species than previously thought.

Natural pathology of the Baboon (Papio spp.)

BACKGROUND

Baboons are useful animal models for biomedical research, but the natural pathology of the baboon is not as well defined as other non-human primates.

METHODS

A computer search for all morphologic diagnoses from baboon necropsies at the Southwest National Primate Research Center was performed and included all the natural deaths and animals euthanized for natural causes.

RESULTS

A total of 10,883 macroscopic or microscopic morphologic diagnoses in 4297 baboons were documented and are presented by total incidence, relative incidence by sex and age-group, and mean age of occurrence. The most common diagnoses in descending order of occurrence were hemorrhage, stillborn, amyloidosis, colitis, spondylosis, and pneumonia. The systems with the most diagnoses were the digestive, urogenital, musculoskeletal, and respiratory.

CONCLUSION

This extensive evaluation of the natural pathology of the baboon should be an invaluable biomedical research resource.