MELANOCYTOMA IN A COW

Introduction In cattle, melanomas are rare and constitutes 1 to 6% of all tumors. Melanomas are neoplastic processes usually observed in the skin. They may be congenital or acquired, in the latter case however in young animals. Darkly colored cattle may be at risk; neither cutaneous site nor gender predilection has been appare nt. Methods A 3 and half-year old Holstein cow was presented due to a mass hanging on the right lateral/dorsal region that had been observed for one year. In this time it increased in si ze. A paravertebral anaesthesia with 2% Lidocaine was performed before the total surgical extirpation of the tumor. Tissue samples of the tumour were fixed in 10% buffered formalin, embedded in paraffin wax, sectioned at 4 μm and stained with hematoxylin and eosin (H&E) for histopathologi cal examination. Results At the gross pathology the extirpated tumour was a 32 x 32 x 16 cm and the total weight was 10.5 kg. Cut section of the neoplasm was bright and blackish and it had a compact consistency with scattered areas of fine white streaks. The hystological sections revealed a normal epidermis with focal slight hyperkeratosis while in the dermis, within an extensive, dense an pinkish collagenous matrix, there were many rounded to polygonal cells, sometimes fusiform, full of dark-brownish and granular pigments (melanin) within the cytoplasm and poorly visible nuclei. The cells were often arranged around small blood vessels. In other fields it was possible to observe elongated and fusiform cell, arranged in whorls. Numerous cells of other fields showed totally lack of melanin granules. Anisocytosis and anisokaryosis were moderate. Mitotic activity was low with 1 mitosis per 10 high-power fields. Conclusions On the base of the clinical, intra-operative and histological data, the diagnosis of melanocytoma was made. The term melanocytoma encompasses the benign forms of melanocytic neoplasms, whereas the term melanoma is used for the malignant forms (Goldschmidt et al., 1998; Marcato et al., 2015). The described tumour was considered benign on the base of the following findings: no other metastatic masses were clinically founded, the extirpated tumour did not infiltrate the upper epidermis and surrounding tissues, mitotic activity was very low and there was no evidence of lymphovascular invasion. In the case described, the surgical extirpation of the benign tumor was complete. Unfortunately, after some months the cow died due to unknown reasons and was discarded without undergoing any post-mortem diagnosis. Therefore it was not possible to share the complete positive outcome of other scientific reports (Pravettoni et al., 2003; Scanzani e Bellotti, 1990; Miller et al., 1995).