Malignant hypomelanotic melanoma of mules. A histologic, immunohistochemical and ultrastructural study of a case with unknown primary site and widespread metastases.
An unusual case of malignant hypomelanotic melanoma occurred in a 15-year-old gray mantle mule with unknown primary site and widespread metastatic growth is described. An ante-mortem examination, the presence of subcutaneous nodules was noted; histologically they are constituted by spindle or polygonal-shaped tumour cells with rare black granules in the cytoplasm; the immunohistochemical procedures showed a large expression of S-100, vimentin and HMB-45 antibodies, suggesting thus a diagnosis of malignant melanoma. Ultrastructural findings, obtained on formalin-fixed paraffin-embedded material, showed characteristic melanosomes and irregular fibrillary centers in nuclei of neoplastic cells. At post-mortem examination, other nodular mostly melanotic lesions were appreciable in lungs, kidneys, brain, liver, pancreas, spleen, lymph nodes and muscles. The importance of immunohistochemical and ultrastructural findings for the differential diagnosis of this neoplasm is emphasized.
Giuffré
G
G
Dipartimento di Patologia Umana, Università di Messina, Italy.
Muscarella
A
A
Muscarà
M
M
Todaro
P
P
Tuccari
G
G
D000818:Animals; D018397:Equidae; D005260:Female; D008545:Melanoma / Q000473:pathology / Q000556:secondary / Q000662:veterinary*; D009382:Neoplasms, Unknown Primary / Q000473:pathology / Q000662:veterinary*; D012983:Soft Tissue Neoplasms / Q000473:pathology / Q000662:veterinary*