Mammary Gland Neoplasia in the Cow - Veterinary Pathology

506 POVEY/~SBORNE
The periphery of the tumour was well demarcated dorsally by dense collagenous
tissue of the deep abdominal fascia in which was incorporated a thin strip
of striated muscle and ventro-laterally by thin but fairly dense collagenous septa
from normal glandular tissue. The neoplastic tissue was densely cellular, with the
typical cell rather ellipsoid, averaging 20 by 15 ,LA, with a central round or oval
nucleus with sharp nuclear membrane, stippling of chromatin, and a variable
number of small nucleoli (Fig. 1). The cytoplasm was eosinophilic and tended to
be drawn out into stellate strands, linking up with the cytoplasmic processes of
neighbouring cells. Mitotic figures were few in number (averaging 1 per 10 fields
at 320 x magnification). A striking feature was the large number of multinucleate
giant cells with up to 30 nuclei, sometimes very hyperchromatic, which tended to
be conglomerated towards the centre of the cell rather than around its periphery.
Approximately 20% of these multinucleate cells were vacuolated (Fig. 2, 3). Unfortunately
no fat stain was carried out and these vacuoles could not be identified
further. However, some vacuoles contained well-stained material suggesting a
possible phagocytic property of at least some of the giant cells. The tumour was
moderately vascular, with some of the venules invaded by tumour cells. Its stroma
was of fine collagen in a pericellular arrangement. Reticulin-staining revealed a
meshwork of argyrophilic fibres surrounding each cell (Fig. 3).
Fig. 3. Peripheral area of tumour. Giant cells, some vacuolated, have many densely
staining nuclei, and are surrounded by a meshwork of argyrophil fibres.
Gomori’s reticulin stain.
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