Chromatophoromas in a pine snake

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.

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.

Cutaneous Chromatophoromas in Captive Snakes

Chromatophoromas are neoplasms arising from pigment-bearing cells (chromatophores) of the dermis. While isolated cases have been reported in the literature, the prevalence and biological behavior of chromatophoromas in snakes are unknown. Forty-two chromatophoromas were identified among 4663 submissions (0.9%) to a private diagnostic laboratory in a 16-year period. The most commonly affected snakes were colubrids (23 cases, 55%) and vipers (8 cases, 19%). The San Francisco garter snake was the most commonly affected species (6 cases; 14% of all affected snake species and 3.7% of all garter snake submissions). No sex predilection was found. The age of 28 snakes ranged from 5 to 27 years. Single cutaneous chromatophoromas were most commonly observed and presented as pigmented cutaneous masses or plaques along any body segment. Euthanasia or death due to progressive neoplastic disease or metastasis was reported in 8 (19%) and 4 (10%) cases, respectively. The survival time of 4 animals ranged from 4 to 36 months. Microscopically, xanthophoromas, iridophoromas, melanocytic neoplasms, and mixed chromatophoromas were identified, with melanocytic neoplasms being most common. Microscopic examination alone was generally sufficient for the diagnosis of chromatophoroma, but immunohistochemistry for S-100 and PNL-2 may be helpful for diagnosing poorly pigmented cases. Moderate to marked nuclear atypia appears to be consistently present in cutaneous chromatophoromas with a high risk of metastasis, while mitotic count, lymphatic invasion, the level of infiltration, and the degree of pigmentation or ulceration were not reliable predictors of metastasis.

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

A dwarf bearded dragon (Pogona henrylawsoni) was presented with a white subcutaneous mandibular mass and multiple nodules in the oral mucosa, heart, liver, kidney, intestine, and visceral fat. Histologically, the tumor consisted of densely packed spindle-shaped cells with brow intracytoplasmic pigment that exhibited white-blue birefringence with polarized light. Immunohistochemical staining was negative for S-100 and weakly positive with melan A. Electron microscopic examination revealed cytoplasmic irregular and oblong empty spaces, laminated and often arranged into short stacks, compatible with reflecting platelet profiles typically seen in iridophores. However, in unstained ultrathin sections, electron-dense crystalline material was present, which filled the empty spaces described for stained sections before. Based on histology, immunohistochemistry, and biologic behavior, a malignant iridophoroma was diagnosed. To the authors' knowledge, iridophoromas in lizards have rarely been characterized by using electronic microscopy. Moreover, this is the first description of an iridophoroma in a dwarf bearded dragon.

Melanophoromas and iridophoromas in reptiles

Chromatophoromas are tumours of pigment-producing cells of the skin and are rarely reported in reptiles. These tumours are subclassified on the basis of the type of pigment. The present study characterizes chromatophoromas arising in 26 reptiles, including six snakes, 19 lizards and a tortoise. These include the first reports of melanophoromas in a yellow anaconda (Eunectes notaeus), pigmy rattlesnake (Sistrurus spp.), southern water snake (Nerodia fasciata), veiled chameleon (Chamaeleo calyptratus) and leopard gecko (Eublepharis macularius); the first reports of benign iridophoromas in a savannah monitor (Varanus exanthematicus), veiled chameleon and bearded dragon (Pogona vitticeps); and the first description of a malignant iridophoroma in a bearded dragon. Additionally, in three bearded dragons a 'mucinous' type of melanophoroma is described for the first time. Chromatophoromas generally arose from the skin of the body and head and ranged in size from 0.2 to 2.0cm in diameter. In six cases the animals were humanely destroyed immediately after diagnosis. Three further animals were humanely destroyed following recurrence of their tumour. Six of these nine reptiles had visceral metastases. Grossly, melanophoromas (n=20) were grey or black, while iridophoromas (n=6) were white in colour. Microscopically, most of the tumours were composed of spindle cells with varying pigmentation and 0-2 mitoses per 10 high power fields. Six of the 20 melanophoromas were classified as malignant due to the presence of intravascular tumour cells, visceral metastases, high pleomorphism and/or mitotic figures. Five of the six iridophoromas were classified as benign and the one malignant tumour was defined by the presence of intravascular tumour cells and visceral metastases. Immunohistochemically, melan A and S100 were coexpressed by all of the chromatophoromas.

Diagnosis and clinical management of multiple chromatophoromas in an eastern yellowbelly racer (Coluber constrictor flaviventris)

A wild-caught subadult eastern yellowbelly racer (Coluber constrictor flaviventris) presented with three raised, circumscribed, freely moveable subcutaneous masses over the dorsal and right epaxial musculature. Microscopic examination and special staining of surgically excised masses were diagnostic for chromatophoroma. No metastases were apparent on whole-body plain film radiographs and computed tomography. Additional excisional biopsies of previously affected sites performed 13 wk later demonstrated normal skin and subcutis. The snake recovered uneventfully and continued to do well 18 mo later. Surgical excision of chromatophoromas remains the treatment of choice in snakes. Subcutaneous masses in snakes should be thoroughly investigated.

Reptile neoplasia: a retrospective study of case submissions to a specialty diagnostic service

This retrospective study appears to be the largest publication to date regarding the prevalence of neoplasia in reptiles. As in previous publications, neoplasia is most common in snakes, followed by lizards, chelonians, and crocodilians. Several interesting trends were documented in this study, some of which appear to be previously unidentified, and some that support the findings of previous publications.