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Other Names: Avian Melanomas
Melanoma is a type of skin cancer. Melanomas are less commonly reported in birds, but have been documented in a variety of avian species, including chickens. Melanomas in birds, except for a few affecting the eye, are almost always malignant.
Melanoma tumors can vary from flattened macule-like areas of pigmentation, to distinct masses that multifocally replace visceral organs. In the reported cases of melanoma in chickens, the most common areas for tumors to develop are the facial region, including the beak and eyelids.
Case 1: Malignant melanoma in a Pigeon. A 12-year-old male pigeon was reported to have a small lesion on the lower beak, which was diagnosed as malignant melanoma. After surgery to remove it, the general condition of the bird worsened and the bird died. Post mortem examination revealed gross, black-colored lesions in the liver, kidney, spleen, and femur bone marrow. Lesions were not found in the adrenals. Histopathologically, the neoplastic cells had a large amount of melanin pigment and showed severe anisokaryosis and prominent nucleoli. Mitotic activity was infrequent but varied considerably where it was observed. Ref Primary tumor site: beakSites of Metastases: liver, kidney, spleen, and femur bone marrow
Case 2: Malignant melanoma in a Penguin. A 20-year-old female macaroni penguin with a large black mass of the beak was examined pathologically. At necropsy, the mass was solid, irregular and black color, and had invaded the upper jaw and the oral cavity. Metastasis of the tumor to the thoracic subcutaneous tissue was also observed. Histopathologically, epithelioid or spindle tumor cells with many intracytoplasmic black pigments and eosinophilic abundant cytoplasm showed a solid, invasive proliferation pattern. Tumor cells were positive for S-100 and PCNA and negative for Desmin and Pan-cytokeratin by an immunohistochemical analysis. Electron microscopically, intracytoplasmic melanin granules and melanosomes were observed. Ref Primary tumor site: beak
Sites of Metastases: Adrenal gland
Case 3: Malignant melanoma in a Cockatoo. A 24-year-old female umbrella cockatoo was examined because of a subcutaneous swelling of the left shoulder. Radiographs of the left wing revealed boney proliferation of the left proximal humerus. At surgery, an unencapsulated infiltrative nonpigmented mass within the subcutaneous tissue and skeletal muscle was identified overlying the left humerus. The mass was surgically excised and submitted for histologic examination; however, the cockatoo died after excision. Histologically, the mass was composed of nests and sheets of pleomorphic neoplastic cells with a high mitotic index and extensive necrosis. Rare neoplastic cells contained fine brown cytoplasmic granules that stained black with Fontana-Masson, confirming the presence of melanin pigment. The histomorphologic diagnosis was consistent with an anaplastic malignant melanoma of subcutaneous tissues. Ref Primary tumor site: wingSites of Metastases: none
Case 4: Malignant melanoma in a Mandarin duck. A biopsy was taken from a mass on the dorsal surface of the bill of an adult female mandarin duck was diagnosed as a malignant melanoma by light microscopy. Two months later, the tumor had enlarged considerably; the duck developed severe dyspnea and was euthanatized. At necropsy, there were metastases to lymphoid tissues in the lower regions of the neck. Ref Primary tumor site: beakSites of Metastases: lymphoid tissues in the neck
Case 5: Malignant melanoma in a Budgie. A 3-year-old male budgerigar was presented for weakness and had a 0.5 cm mass located on the left patagium. Ref Primary tumor site: patagiumSites of Metastases: none
Case 6: Malignant melanoma in a Parrot. A male thick-billed parrot was diagnosed with a malignant melanoma of the mandibular beak (gnathotheca). Surgical excision was impossible because of the location of the lesion; a combination of radiation therapy and oral antitumor drugs were used to treat the neoplasm. A whole-body computed tomographic scan showed evidence of metastasis in the lungs; the bird, therefore, was considered to have stage IV disease. Throughout the treatment period, the bird showed no clinical evidence of systemic disease. The bird was given 20 treatments of localized radiation therapy of 2.5 Gray (Gy) for a cumulative dose of 50 Gy. The bird was also treated with piroxicam and cimetidine orally from the time of diagnosis, throughout radiation therapy, and until its death. By the completion of radiation therapy, the initial lesion had decreased considerably in size. The bird survived 2.5 months after radiation therapy was completed but died of complications related to metastatic disease. Necropsy results revealed métastases throughout the body, including lesions in the lungs and liver. The radiation therapy did produce tumor response in the form of a reduction in size of the visible tumor. Ref Primary tumor site: beakSites of Metastases: lungs
Case 7: Malignant melanoma in a Penguin. A 20-year-old, female African grey parrot was examined because of ataxia and weakness. Radiographs were unremarkable, and results of a complete blood cell count revealed leukocytosis and heterophilia. Because of poor response to therapy with meloxicam, doxycycline, and enrofloxacin; deteriorating condition; and poor prognosis, the parrot was euthanized. Postmortem examination revealed 2 dark red nodules in the liver. No grossly visible mass was observed in the syrinx. Histologic examination of the liver and syrinx revealed similar foci of round, oval, and polygonal cells exhibiting severe pleomorphism, with poorly demarcated cytoplasmic borders and moderate amounts of eosinophilic cytoplasm containing brown to black granules (melanin). The mitotic index was 15. The presence of melanin pigment is consistent with a diagnosis of melanoma at both sites. The multifocal distribution and intravascular invasion indicate metastasis; however, the site of origin was unknown Ref Primary tumor site: syrinxSites of Metastases: none
Case 8: Malignant melanoma in a Zebra finch. A 3 year old adult male zebra finch developed a large darkly pigmented tumor in the coelom, extended from the apex of the heart to the cloaca. It was adherent to the intestines and the ventriculus. Dark small masses (likely metastases) were observed in the lungs. Cytologically, the neoplasm consisted mainly of round to oval cells with brown or pale blue to blue-brown pigment. Lesser numbers of cells were stellate to dendritic with abundant amounts of brown pigment granules or were markedly pleomorphic with variable amounts of pigment. Histologically, the tumor consisted of dense sheets and aggregates of infiltrative melanocytes that were negative for S 100 and Melan A. A few cells were consistent with “signet ring” melanocytes. Melanocytes examined by electron microscopy contained typical structures, mainly premelanosomes and melanosomes, of this cell type. Ref Primary tumor site: coelomSites of Metastases: lungs
Case 9: Malignant melanoma in a Duck. An adult male Muscovy Pekin duck cross had a primary malignant uveal melanoma with periocular extension involving the left eye. The periocular mass displaced the globe 1.5 cm laterally. Thoracic metastasis of the ocular neoplasm infiltrated the pectoral muscles, rib cage, and cranial lung lobe on the left side, causing diminished voluntary motion of the left wing. The left orbit was exenterated, but tumor regrowth was evident within 2 weeks. Ref Primary tumor site: eyeSites of Metastases: pectoral muscles, rib cage, lungs
Case 10: Malignant melanoma in a Seagull. A common seagull was found near the southern coast of Italy by the veterinarians of the local wild animal rescue center. Physical examination of the bird revealed an ulcerated mass involving a majority of the oral cavity; the mass did not allow for normal feeding. After the bird died necropsy was performed and the mass was histologically and immunohistochemically examined. The morphology and the immunoreactivity for Melan-A and S-100 antigens led to a diagnosis of malignant melanoma. Ref Primary tumor site: oral cavitySites of Metastases: none
Case 11: Malignant melanoma in a Parrot. A 20-year-old, female African grey parrot was examined because of ataxia and weakness. Radiographs were unremarkable, and results of a complete blood cell count revealed leukocytosis and heterophilia. Because of poor response to therapy with meloxicam, doxycycline, and enrofloxacin; deteriorating condition; and poor prognosis, the parrot was euthanatized. Postmortem examination revealed 2 dark red nodules in the liver. No grossly visible mass was observed in the syrinx. Histologic examination of the liver and syrinx revealed similar foci of round, oval, and polygonal cells exhibiting severe pleomorphism, with poorly demarcated cytoplasmic borders and moderate amounts of eosinophilic cytoplasm containing brown to black granules (melanin). The mitotic index was 15. The presence of melanin pigment is consistent with a diagnosis of melanoma at both sites. The multifocal distribution and intravascular invasion indicate metastasis; however, the site of origin was unknown. Ref Primary tumor site: syrinxSites of Metastases: liver