Neoplasia
12
Abstract
A neoplasm represents an altered process involving abnormal and uncontrolled growth of
cells that is usually detrimental to the host. Neoplasm are classified as benign or malignant
and named according to the features of differentiation recognised through histological
examination, thus reflecting the tissue of origin. Neoplasia can arise following exposure to
certain chemicals, heavy metals, ionizing radiation, chronic inflammation, ultraviolet radiation, certain viruses and pollution. The chapter covers a selection of reported neoplastic
conditions affecting fish although overall, many of the cause(s) have not been determined.
Keywords
Neoplasia Salmon Trout
A neoplasm is an altered process involving abnormal and
uncontrolled growth of cells that is usually detrimental to
the animal. They are named according to the features of
differentiation recognised through histological examination,
thus reflecting the tissue of origin. In this context, neoplasm
and tumour are interchangeable terms in current medical
usage. The abnormal cell type may continue to increase
even after the initiating mutagen is no longer present and
generally more than one mutation is necessary for oncogenesis. Neoplasia can arise following exposure to certain
chemicals, heavy metals, ionizing radiation, chronic inflammation, ultraviolet radiation, certain viruses and pollution.
They are classified as benign or malignant (i.e. to include
anaplasia, frequent mitotic figures and infiltration of
neutrophils), but overall many of the cause(s) have not been
determined. Examples of neoplasia representing a range of
tissue origins are discussed.
12.1 Papilloma
Atlantic salmon papillomatosis is an epidermal benign neoplasia on the skin and scales of salmon parr in their second
summer, but also occasionally of young adult fish (smolts
and grilse) which have adapted to sea water.
The growths appear as single or multiple with a smooth to
nodular texture, and range from white to brown or pink. Each
papilloma may vary from a few millimetres to complex
growths of up to 40 mm (Fig. 12.1). In heavily affected fish
more than half of the body surface may be covered. Histologically, it is a plaque-like proliferation of the epidermis
(Fig. 12.2). Each plaque is a stratified squamous epithelium
with supporting stroma, hyperplastic epidermal cells containing prominent nucleoli with numerous atypical mitotic
figures. There is usually little dermal involvement. The number of mucous cells is reduced and the basement membrane
absent or indistinct. The papilloma is relatively harmless to
the fish and eventually detaches allowing the skin to heal.
Electron microscopy studies of papillomas have indicated
that virions with herpesvirus morphology are sometimes
associated with the growth. Attempts to isolate this agent
in culture have failed and therefore, the cause (or possibly
causes) of papillomatosis remains unknown.
12.2 Chondroma
Single, firm, ovoid, white, smooth growths involving the
branchial cartilage have been reported in salmonids and
diagnosed as a benign cartilaginous neoplastic growth or
D.W. Bruno et al., A Colour Atlas of Salmonid Diseases,
DOI 10.1007/978-94-007-2010-7_12, # Springer Science+Business Media B.V. 2013
187
12
Abstract
A neoplasm represents an altered process involving abnormal and uncontrolled growth of
cells that is usually detrimental to the host. Neoplasm are classified as benign or malignant
and named according to the features of differentiation recognised through histological
examination, thus reflecting the tissue of origin. Neoplasia can arise following exposure to
certain chemicals, heavy metals, ionizing radiation, chronic inflammation, ultraviolet radiation, certain viruses and pollution. The chapter covers a selection of reported neoplastic
conditions affecting fish although overall, many of the cause(s) have not been determined.
Keywords
Neoplasia Salmon Trout
A neoplasm is an altered process involving abnormal and
uncontrolled growth of cells that is usually detrimental to
the animal. They are named according to the features of
differentiation recognised through histological examination,
thus reflecting the tissue of origin. In this context, neoplasm
and tumour are interchangeable terms in current medical
usage. The abnormal cell type may continue to increase
even after the initiating mutagen is no longer present and
generally more than one mutation is necessary for oncogenesis. Neoplasia can arise following exposure to certain
chemicals, heavy metals, ionizing radiation, chronic inflammation, ultraviolet radiation, certain viruses and pollution.
They are classified as benign or malignant (i.e. to include
anaplasia, frequent mitotic figures and infiltration of
neutrophils), but overall many of the cause(s) have not been
determined. Examples of neoplasia representing a range of
tissue origins are discussed.
12.1 Papilloma
Atlantic salmon papillomatosis is an epidermal benign neoplasia on the skin and scales of salmon parr in their second
summer, but also occasionally of young adult fish (smolts
and grilse) which have adapted to sea water.
The growths appear as single or multiple with a smooth to
nodular texture, and range from white to brown or pink. Each
papilloma may vary from a few millimetres to complex
growths of up to 40 mm (Fig. 12.1). In heavily affected fish
more than half of the body surface may be covered. Histologically, it is a plaque-like proliferation of the epidermis
(Fig. 12.2). Each plaque is a stratified squamous epithelium
with supporting stroma, hyperplastic epidermal cells containing prominent nucleoli with numerous atypical mitotic
figures. There is usually little dermal involvement. The number of mucous cells is reduced and the basement membrane
absent or indistinct. The papilloma is relatively harmless to
the fish and eventually detaches allowing the skin to heal.
Electron microscopy studies of papillomas have indicated
that virions with herpesvirus morphology are sometimes
associated with the growth. Attempts to isolate this agent
in culture have failed and therefore, the cause (or possibly
causes) of papillomatosis remains unknown.
12.2 Chondroma
Single, firm, ovoid, white, smooth growths involving the
branchial cartilage have been reported in salmonids and
diagnosed as a benign cartilaginous neoplastic growth or
D.W. Bruno et al., A Colour Atlas of Salmonid Diseases,
DOI 10.1007/978-94-007-2010-7_12, # Springer Science+Business Media B.V. 2013
187