Elise E. B. LaDouceur

Diagnosis and classification of ovarian epithelial neoplasms in guinea pigs ( Cavia porcellus ) are challenging due to inconsistent terminology and few available diagnostic criteria. This study evaluated 23 ovarian epithelial neoplasms in 15 guinea pigs with the objectives of (1) differentiating ovarian surface epithelial (OSE) neoplasms from rete ovarii neoplasms using immunohistochemistry, (2) describing salient histologic features, and (3) classifying neoplasms according to canine, human, and rodent classification schemes. PAX-8 immunohistochemistry separated immunoreactive rete neoplasms from nonreactive OSE neoplasms. OSE neoplasms ( n = 12) were well-differentiated and arose directly from the ovarian surface, rather than the primarily cortical location of OSE neoplasms in other species. Focal OSE neoplasms with papillary projections on a fibrous core or tubules within a fibrous stroma were classified as surface papilloma and surface adenoma, respectively. Generalized OSE neoplasms with tubules, papillae, and fibrous stroma were classified as surface borderline tumors. Neoplasms with invasion, 2–4 mitotic figures per 2.37 mm ² , and/or peritoneal implantation were classified as surface carcinoma. The only carcinoma with follow-up had resolution of clinical signs and no radiologic evidence of recurrence 6 months after ovariohysterectomy. Rete neoplasms ( n = 11) included rete cystadenomas and rete adenomas, and consisted of epithelial cells arranged in papillae and tubules within a rete tubule, with or without cysts, respectively. Further investigation is needed to correlate diagnoses with neoplasms’ biologic behavior. We propose using “surface” and “rete” in the diagnosis to denote location, rather than “papillary,” “cystic,” or “serous,” which are variably used in other ovarian neoplasia classification schemes, to standardize terminology.

Ulcerative dermatitis is common in captive cephalopods and often results from trauma to their delicate epidermis with subsequent infection by opportunistic pathogens. We report 3 cases of fatal ulcerative dermatitis caused by a rare pathogen in a cohort of captive, adult, north Pacific big eye octopuses ( Octopus californicus ). Abundant, 5 to 8 µm diameter, roughly spherical organisms, often located in pairs or clusters, were infiltrating the ulcers in all 3 cases. Ultrastructurally, the organisms possessed multilamellated to scaley cell walls and were surrounded by empty, irregularly ovoid, 1 μm diameter, membrane-bound structures consistent with an ectoplasmic net. These features are consistent with thraustochytrid, a marine saprophyte. Previous reports of pathogenic thraustochytrid infections in cephalopods are rare, suggesting this is an uncommon albeit serious infection in captive cephalopod populations.

There are no previous publications on diseases of Japanese isopods ( Bathynomus doederleinii ) or giant deep-sea isopods ( Bathynomus giganteus ). Halioticida noduliformans is a pathogenic oomycete that infects external tissues of abalone, mantis shrimp, and European lobsters, and has not been previously reported in isopods. The purpose of this study is to describe the clinical presentation, gross findings, and histologic lesions caused by H. noduliformans in B. doederleinii and B. giganteus kept in a public aquarium in California. Oomycetes caused inflammation and necrosis in the body wall, gills, hepatopancreas, eyes, and gut. Our study demonstrates that this pathogen occurs in a previously unreported geographic location and in previously unpublished hosts. H. noduliformans infected both external and internal viscera, the latter of which has not been previously reported in any host species. H. noduliformans has variable pathogenicity depending on the host species and was considered the cause of death in these isopods.

Papillomas, many of which are virally induced, are common proliferative cutaneous and mucocutaneous lesions in multiple species, exhibiting characteristic histologic cytopathic changes that distinguish them from nonviral squamous papillomas. A single case report of a novel papillomavirus, Ursus maritimus papillomavirus-type 1, in a polar bear has been reported without investigation into any association between this virus and papilloma formation. We identified papillomas in 3 polar bears. All 3 cases had pedunculated masses consistent with papillomas (i.e., proliferative epithelium forming papillary projections on a fibrovascular stalk); case 1 also exhibited koilocytosis (cytopathic change), consistent with a viral papilloma. Polymerase chain reaction (PCR) using primers that can amplify a diversity of papillomaviruses followed by amplicon sequencing yielded a novel papillomavirus sequence in case 1, which shared <70% nucleotide identity to any known papillomavirus type, indicative of a putatively novel papillomavirus. In situ hybridization (ISH) of case 1 demonstrated viral nucleic acid within proliferative cells and not within the adjacent normal skin, suggesting the virus was the causative agent of this papilloma. The squamous papillomas in cases 2 and 3 were negative for papillomavirus by both PCR and ISH. These findings support our hypothesis that cytopathic effect is associated with the presence of papillomavirus in polar bears, while the lack of histologic cytopathic change may predict nonviral pathogenesis. Further sequencing of the putatively novel viral genome will benefit research and conservation efforts of polar bears.

There are few reports describing spontaneous neoplasms in cynomolgus macaques, despite the frequent use of this species in laboratory research. This report describes cytologic, histologic, and immunohistochemical findings of a cutaneous to subcutaneous nerve sheath tumor located within the haired skin of the abdomen of a 2.5-y-old, intact, female, captive Mauritius cynomolgus macaque. The nerve sheath tumor was well demarcated, partially encapsulated, densely cellular, and extended from the subcutis to the most superficial dermis, abutting the epidermis. Neoplastic cells formed intersecting streams and had a high mitotic count (18 per 2.37 mm²). Due to the substantial morphologic overlap of this neoplasm with amelanotic melanoma, particularly the close association with the epidermis, immunohistochemistry was required for definitive diagnosis. Neoplastic cells were immunoreactive to vimentin, S-100, SOX10, laminin, collagen IV, and CD56, and negative for melan-A, tyrosinase, MITF, and HMB45. This immunohistochemical profile is diagnostic for nerve sheath tumor based on human and canine criteria and rules out amelanotic melanoma. Despite incomplete excision, the nerve sheath tumor had not grossly recurred after 1 mo, at which point the animal was euthanized for unrelated reasons. This report underscores the importance of using an immunohistochemical panel in cases of cutaneous and subcutaneous spindle cell neoplasms, as there is substantial morphologic and immunohistochemical overlap between nerve sheath tumors and melanocytic neoplasms due to their shared neuroectodermal origin. To our knowledge, this is the first report of a nerve sheath tumor in a cynomolgus macaque, and one of the few reports of spontaneous neoplasia in this species.