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The necropsy (Time 6) examination of a dog with metastatic amelanotic melanoma in thoracic cavity. A-Multiple whitish and firm masses interspersed with reddish and soft areas adhered to parietal pleura occupying 80% of the lung parenchyma. B-Mass of cartilaginous tissue with few spindle and epithelioid neoplastic cells (H&E).
Source publication
Background: Melanomas are typically malignant neoplasms commonly observed in the oral cavity of dogs. The classical presentation of melanomas with characteristic melanin pigmentation is easy to diagnose; however, in some cases, the lack of melanin production in the amelanotic oral tumors cause a delay in establishing the precocious diagnosis and co...
Contexts in source publication
Context 1
... imaging after thoracentesis displayed radiopacity in the left cranial thorax. The necropsy revealed an intense hydrothorax and multiple whitish and firm masses interspersed with reddish and soft areas, ranging from 3 to 10 cm in diameter, and occupying 80% of the lung parenchyma ( Figure 6A). The microscopic evaluation demonstrated many masses of cartilaginous tissue with few spindle and epithelioid neoplastic cells at the periphery of the parenchyma ( Figure 6B). ...
Context 2
... necropsy revealed an intense hydrothorax and multiple whitish and firm masses interspersed with reddish and soft areas, ranging from 3 to 10 cm in diameter, and occupying 80% of the lung parenchyma ( Figure 6A). The microscopic evaluation demonstrated many masses of cartilaginous tissue with few spindle and epithelioid neoplastic cells at the periphery of the parenchyma ( Figure 6B). Melan-A positive cells were found around and inside some cartilage cells. ...
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Research on melanogenesis, its regulation in health and disease, and the discovery of new molecules with pigmenting and depigmenting activities use different models. Here we standardize a protocol based on previous ones using primary human melanocytes and keratinocytes in co-cultures, in which melanogenesis was induced under mild conditions by the...
Citations
A 9-year-old intact male Brazilian Mastiff dog with a 1-year history of progressive severe swelling in all four limbs and significant locomotory difficulty was euthanized due to unresponsiveness to medical management. Macroscopically, the distal phalanx of the 5th digit of the left hindlimb was replaced by a cutaneous, non-ulcerated, 3.0 cm diameter, multilobulated, black, firm nodule. The cortical bones of the appendicular skeleton were thickened and partially effaced by infiltrative coalescing nodules (0.1–1.0 cm diameter). The lungs, heart, pleura, mesentery, adrenal glands and kidneys were infiltrated by similar nodules (0.5–3.5 cm diameter). Histological evaluation of the masses revealed a non-encapsulated malignant neoplasm composed of spindloid to polygonal cells that contained variable amounts of intracytoplasmic melanin and were arranged in haphazardly interlacing streams and bundles supported by scant fibrovascular stroma with myxoid and chondroid matrix formation. Neoplastic cells had intense cytoplasmic labeling for S100 and 10% had moderate cytoplasmic immunoreactivity for Melan-A. To the authors’ knowledge, this is the first description of a canine metastatic digital chondrogenic melanocytic tumour with strongly suggestive chondroid differentiation of neoplastic melanocytes.
