Page 586 - The Veterinary Laboratory and Field Manual 3rd Edition

Necropsy guidelines 523

male dogs in which chronic androgen stimulation
results in hyperplasia of the gland which gradu-
ally narrows and occludes the urethra resulting
in dysuria (see Figure A2.9). While hyperplasia
is reversible in some cases it can be viewed as a
pre-neoplastic process increasing the chance of
neoplastic transformation in a tissue.
Hyperplasia must be differentiated from neo-
plasia. This may require putting the lesion into
context with other features of the case or require
histopathology.

neoplasia

Neoplasia results from irreversible alteration in
mechanisms controlling the cell cycle and cell
division. Neoplasia can be benign character-
ized by localized, expansile growth or malignant
associated with invasive growth, metastasis, Figure A2.10 Liver, sheep. Chronic fasciolia-
and other paraneoplastic effects. Benign neo- sis (Fasciola hepatica). F. hepatica is a liver fluke
plasia is usually associated with the formation commonly associated with acute and chronic liver
of a mass within an organ or tissue and will be disease in small ruminants. Acute disease mani-
circumscribed or encapsulated. Dependent on fests as sudden death as a result of overwhelming
location mass effect of a benign growth can be hepatocellular necrosis caused by large number of
associated with clinical signs. Peripheral nerve larval flukes migrating through the parenchyma.
sheath tumour for example will often be associ- Chronic fascioliasis occurs are a result of chronic
ated with neuropathy. Malignant neoplasia will cholangiohepatitis as a result of the presence of
grossly appear infiltrative and is often associated adult flukes within bile ducts. In this image, a tangle
with areas of central necrosis as a result of rapid of adult flukes can be seen within the lumen of a
growth leading to ischaemia. large bile duct at the hilus. The left lobe is atrophic,
fibrotic bile ducts are visible from the cut section
and the right lobe is hypertrophied. This appearance
atrophy is characteristic but it is unclear why the left lobe is
preferentially affected. In addition, the hilar lymph
Atrophy is the reduction in size of an organ or nodes are enlarged as a result of chronic antigenic
tissue as a result of reduction in size or num- stimulation. See also Plate 49. Photo courtesy of Mr
ber of component cells. This occurs as a result R. Irvine, University of Glasgow, UK.
of withdrawal of trophic factors which may
include blood supply, innervation, or hormonal
stimulation. As with hyperplasia this may be after chronic disuse or denervation. Pathological
physiological, as in atrophy of hyperplastic atrophy is often seen as a sequelae to chronic
mammary tissue at the end of lactation or be inflammation (Figure A2.10).
pathological as may occur in skeletal muscle

Vet Lab.indb 523 26/03/2019 10:26