HISTOLOGIC, IMMUNOHISTOCHEMICAL, AND ELECTRON MICROSCOPIC CHARACTERIZATION OF A MALIGNANT IRIDOPHOROMA IN A DWARF BEARDED DRAGON (POGONA HENRYLAWSONI)

Evaluation of Neoplasia, Treatments, and Survival in Lizard Species

Neoplasia has been reported in lizards, but more research is needed to accurately document the prevalence and prognosis of the various known neoplasms that affect lizards. This study reviewed medical records from an online database, the Exotic Species Cancer Research Alliance (ESCRA), and reviewed published literature to determine the prevalence of neoplasia, malignancy, metastasis, treatment strategies, and outcomes by species and sex. Records from 55 individual lizards, 20 different species, and 37 different tumors were identified. In the literature, 219 lizards, 59 species, and 86 unique tumors were identified from 72 published case reports. Potential signalment factors such as age, sex, and species were evaluated to see if they affected case outcome. Additional factors including neoplasia type, presence of metastasis, and types of pursued treatments were also evaluated. Statistical analysis was performed to determine whether a factor was significantly associated with animal death due to the identified neoplasia or with animal survival or death due to other causes (non-neoplastic outcomes). Komodo dragons and savannah monitors were more likely to die from neoplasia compared to other lizard species. Cases where the status of metastasis was unknown were significantly associated with death due to neoplasia. Having an unknown status of male versus female was significantly associated with non-neoplastic outcomes of death. Leukemia and islet cell carcinoma were significantly associated with death due to neoplastic causes. Chondrosarcoma, myxosarcoma, osteosarcoma, and squamous cell carcinoma were significantly associated with non-neoplastic outcomes of death. Surgery alone and radiation therapy alone each were significantly associated with non-neoplastic outcomes of death, while lizards not receiving treatment were significantly associated with death due to neoplasia. Benign neoplasia was significantly associated with non-neoplastic outcomes of death. These results will aid in the improved diagnosis and management of neoplasia in lizard species, as well as expanding our understanding of prognostic indicators of neoplasia in lizards.

Chromatophoromas in Reptiles

Chromatophoromas are neoplasms that arise from pigment cells of reptiles, amphibians, and fish. They include melanophoromas (melanomas), iridophoromas, and xanthophoromas. Most chromatophoromas develop spontaneously, but genetic and environmental factors may also play a role in their oncogenesis. The diagnosis is typically through histologic examination. Immunohistochemistry and electron microscopy can be helpful for diagnosing poorly differentiated and/or poorly pigmented neoplasms. Aggressive surgical excision is the current treatment of choice. This review describes the clinical presentation, gross appearance, diagnostic applications, clinical behavior, and treatment of chromatophoromas in reptiles.

Gross, histologic, and immunohistochemical characteristics of cutaneous chromatophoromas in captive bearded dragons

Chromatophoromas are neoplasms that develop from the dermal pigment-bearing and light-reflecting cells (chromatophores) in the skin of reptiles, fish, and amphibians. Seventeen cutaneous chromatophoromas were identified from 851 bearded dragon submissions (2%) to a private diagnostic laboratory in a 15-y period. No sex predilection was found. Ages ranged from 9 mo to 11 y. Chromatophoromas most commonly were single, raised, variably pigmented masses or pigmented scales on the trunk, and less commonly the extremities or head. Microscopically, iridophoromas, melanophoromas, mixed chromatophoromas, and nonpigmented chromatophoromas were identified. Neoplasms were often ulcerated and invaded deep into the subcutis and muscle. Most commonly, nuclear atypia was mild-to-moderate, and mitotic count was low. Six neoplasms had abundant, periodic acid-Schiff-positive, mucinous stroma. Histologic examination was often adequate to diagnose chromatophoromas in bearded dragons given that 11 of 17 had some degree of pigmentation, although it was often scant. IHC for S100 and PNL2 could be helpful to diagnose poorly pigmented neoplasms. No lymphatic invasion or metastases at the time of excision were noted in any of the cases. Follow-up data were available for 6 cases, with no reports of recurrence or neoplasia-related death. Two cases had elevated mitotic counts and nuclear pleomorphism, which has been associated with metastasis in other reports of bearded dragon chromatophoromas. In general, it appears that aggressive surgical excision is often curative, but monitoring may be warranted for cases in which tumors had high mitotic count and nuclear pleomorphism.

Genetics of white color and iridophoroma in "Lemon Frost" leopard geckos

The squamates (lizards and snakes) are close relatives of birds and mammals, with more than 10,000 described species that display extensive variation in a number of important biological traits, including coloration, venom production, and regeneration. Due to a lack of genomic tools, few genetic studies in squamates have been carried out. The leopard gecko, Eublepharis macularius, is a popular companion animal, and displays a variety of coloration patterns. We took advantage of a large breeding colony and used linkage analysis, synteny, and homozygosity mapping to investigate a spontaneous semi-dominant mutation, “Lemon Frost”, that produces white coloration and causes skin tumors (iridophoroma). We localized the mutation to a single locus which contains a strong candidate gene, SPINT1, a tumor suppressor implicated in human skin cutaneous melanoma (SKCM) and over-proliferation of epithelial cells in mice and zebrafish. Our work establishes the leopard gecko as a tractable genetic system and suggests that a tumor suppressor in melanocytes in humans can also suppress tumor development in iridophores in lizards.

The squamates (lizards and snakes) comprise a diverse group of reptiles, with more than 10,000 described species that display extensive variation in a number of important biological traits, including coloration. In this manuscript, we used quantitative genetics and genomics to map the mutation underlying white coloration in the Lemon Frost morph of the common leopard gecko, Eublepharis macularius. Lemon Frost geckos have increased white body coloration with brightened yellow and orange areas. This morph also displays a high incidence of iridophoroma, a tumor of white-colored cells. We obtained phenotype information and DNA samples from geckos in a large breeding colony and used genome sequencing and genetic linkage analysis to localize the Lemon Frost mutation to a single locus. This locus contains a strong candidate gene, SPINT1, a tumor suppressor implicated in human skin cutaneous melanoma. Together with other recent advances, our work brings reptiles into the modern genetics era.

Cutaneous Chromatophoromas in Four Species of Australian Elapid Snake

This report documents the clinicopathological features of cutaneous chromatophoromas in four wild-caught, captive Australian elapid snakes: a strap-snouted brown snake (Pseudonaja aspidoryncha), a tiger snake (Notechis scutatus), an Eastern brown snake (Pseudonaja textilis) and a Mengden's brown snake (Pseudonaja mengdeni). All tumours were subclassified as melanophoromas, with three assessed as malignant on the basis of invasive growth or presence of intracoelomic metastases. The chromatophoromas were single or multiple, black or orange pigmented, cutaneous, sometimes ulcerated, plaques or nodules. Microscopically, the neoplastic cells were often spindle shaped with low or variable pigmentation. Neoplastic cells in one tumour were notable for their pleomorphic round cell morphology and high mitotic rate. One snake with late-stage metastasis survived for over 5 years. There are few reports of chromatophoromas in elapid snakes and, to our knowledge, this is the first report of these tumours in Australian elapid snakes.

Iridophoroma associated with the Lemon Frost colour morph of the leopard gecko (Eublepharis macularius)

The Lemon Frost is a new colour morph of the leopard gecko, which emerged in ca. 2015 as a result of selective breeding and spontaneous mutation. According to multiple breeders observation of Lemon Frost inbreeding with wild-type leopard geckos, Lemon Frost seems to be a codominant trait. Additionally breeders observed another, presumably associated trait - tumour-like skin lesions. Three private-owned Lemon Frost morph leopard geckos with tumour-like skin lesions were admitted to our clinic for examination, which included histopathology, X-ray and ultrasonography. The histopathological investigation of the biopsies indicated malignant iridophoroma; however, no changes were observed in diagnostic imaging. This research is the first report of clinical and histopathological findings of iridophoroma in leopard geckos.

Cutaneous iridophoroma in a Green iguana ‬‬‬‬‬‬‬‬‬‬‬‬‬(Iguana iguana)‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬

An 11-year-old intact male Green iguana (Iguana iguana) was referred for treatment of a probable iridophoroma based on previous cytopathology. A periocular mass was present near the right medial canthus. Computed tomography did not show any sign of metastasis. Clinicopathologic abnormalities included lymphopenia and hyperproteinemia. Cytologic and histologic evaluations of the mass were consistent with iridophoroma. Complete surgical excision of the mass was not possible without removal of the orbit due to local tissue involvement. Recovery and suture removal were unremarkable. Adjunctive radiation therapy was recommended, but not performed. A year later, the surgical site had healed well. To our knowledge, this is the first reported chromatophoroma cytopathology in a Green iguana. Chromatophoromas should be included in the differential diagnoses of pigmented skin tumors in reptiles. Early surgical excision is useful to limit local tissue destruction and metastatic potential.

Oncology of Reptiles: Diseases, Diagnosis, and Treatment

Based on necropsy review, neoplasia in reptiles has a comparable frequency to that of mammals and birds. Reptile neoplasia is now more frequently diagnosed in clinical practice based on increased use of advanced diagnostic techniques and improvements in reptilian husbandry allowing greater longevity of these species. This article reviews the current literature on neoplasia in reptiles, and focuses on advanced diagnostics and therapeutic options for reptilian patientssuffering neoplastic disease. Although most applied clinical reptile oncology is translated from dog and cat oncology, considerations specific to reptilian patients commonly encountered in clinical practice (turtles, tortoises, snakes, and lizards) are presented.

Anatomy and Disorders of the Oral Cavity of Reptiles and Amphibians

A wide variety of disorders may be seen affecting the reptile and amphibian oral cavity. Owners can easily miss problems until they are at an advanced stage because of the difficulty of examining the oral cavity at home. Because many problems are secondary to an inappropriate environment or diet and may be related to systemic disease, a full history and clinical examination is always required. Treatment of oral disorders also requires a holistic approach including correction of any predisposing factors in order for long-term successful resolution of the problem.