Mammary Gland Neoplasia in the Cow - Veterinary Pathology

508 POVEY/OSBORNE
More centrally there were noticeably fewer giant cells, and those present had
fewer nuclei. The cell type was more typically spindle shaped and there was a
definite tendency for streaming and whorling patterns to be formed (Fig. 4, 5).
Mitotic figures were more frequent.
At the edge of the central cavity with blood clots and tissue debris there
was disruption of vessel walls with haemorrhage. In other vessels there were
thrombi with numerous white cells many of which were eosinophils.
The more nearly normal udder was a recently active gland beginning to involute.
Adjacent to the tumour, although well separated by collagenous tissue,
there was pressure collapse of the acini. There were some foci of plasma cells,
neutrophils, and eosinophils in the interstitium.
The tumour was negative for alkaline phosphatase when stained by GOMORI’S
modified method, whereas apparently normal udders gave a positive reaction.
Myoepithelial cells are particularly rich in this enzyme13.
The tumour’s cell type and its pattern of growth, particularly as seen in the
deeper parts with the collagenous and reticulin networks, were considered typical
of a fibroblastic neoplasm. In view of its cellularity, and peripherally more disorganised
structure, with the numerous giant cells, it was classified as a fibrosarcoma
rather than a fibroma, although there was no evidence of any metastasis in the
supramammary lymph nodes, or elsewhere.
The possibility of the lesion being basically an infective granuloma was considered,
but neither bacterium, yeast, nor fungus, was found in the histological
sections.
Discussion
KENNY27, in a complete account of a primary adenocarcinoma of a bovine
udder, considered the rarity of neoplasia of the mammary gland in the cow difficult
to explain, ‘especially when one considers the demands which are made on this
organ by present-day intensive methods of milk production, its proneness to
chronic mastitis, and the fact that the dairy cow, unlike the majority of bovines is
as a rule allowed to live well beyond what is described as the ‘cancer age”. ANDER-
SON and JARRETT~ suggested, however, that as in women lactation is known to
protect against mammary neoplasia, the almost constant lactation in cows may
afford similar protection. FIDLER, ABT, and BRODEY’S postulated that excessive progesterone
stimulation with recurrent milk retention be the key to the high incidence
of mammary neoplasia in the bitch. RENK~~ described how cysts of various
sizes could be found in the glandular tissue in cases of chronic bovine mastitis,
which he likened to ‘mastopathia cystica’ in man. In 1 case he described such change
proceeding to neoplasia in the form of a papillary cyst-adenoma. ROTHENBACHERS6
suspected that some cases which were diagnosed as chronic bovine mastitis may
have been neoplastic in nature.
Pure fibrosarcoma of the mammary gland, in the dog at least, is much less
common than mixed or glandular tumours. Thus SMITH and JONES.~~ in their compilation
of tumours from various surveys included 934 canine mammary tumours
of which only 19 were fibromata or fibrosarcomata. In the cow, as far as we are
aware, apart from intercanalicular fibromatad1 and cisternal fibrous polyps25, there
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