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Tumours of the
Adrenal Medulla |
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Tumours of the adrenal medulla may produce
excess adrenaline/noradrenaline
or their breakdown products.
The two principal types of tumour of the adrenal medulla are phaeochromocytomas
(occurring in adults)
and neuroblastomas (occurring in children).
PHAEOCHROMOCYTOMA
Phaeochromocytoma is a tumour of the adrenaline- and noradrenaline-
(epinephrine- and
norepinephrine-) secreting cells of the adrenal medulla.
It produces high levels of both hormones and their breakdown products, vanyl
mandelic acid
(VMA) and homovanillic acid (HVA), both of which are excreted in the urine and
can be
estimated as a diagnostic test.
The excessive amine production produces hypertension that is often initially
paroxysmal
and associated with severe headaches.
Phaeochromocytoma is one of the causes of surgically treatable systemic
hypertension.
The tumour is usually spherical and less than 5 cm in diameter. It has a pale,
creamy cut surface that changes to dark brown almost instantly when exposed to
air, due to
oxygenation of tumour pigments. Despite the fact that the tumour is usually
small and
non-metastatic, it is a hazardous condition with high peri-operative mortality.
Bilateral tumours are more commonly seen in patients with the relevant MEN
syndrome
Phaeochromocytoma may rarely occur in extra-adrenal sympathetic tissue, mainly
in the retroperitoneal
area alongside the abdominal aorta (organ of Zuckerkandl).
NEUROBLASTOMA
Neuroblastoma of the adrenal medulla is an important malignant tumour in
children
Tumours arise from the adrenal medulla and from the sympathetic
ganglia of the autonomic nervous system.
It is one of the group of peripheral primitive neuroectodermal tumours (PNETs).
Most tumours
occur in children under the age of 3 years, the majority occurring in children
under
the age of one year.
Macroscopically, tumours range from small nodules to enormous masses.
Tumours frequently involve bone marrow, and neuroblastoma often presents with
bone metastasis.
Histologically, tumours are composed of mitotically active small primitive
neuroblastic
cells which exhibit variable degrees of neuronal maturation.
Some tumours contain areas of mature ganglion cells in addition to neuroblastic
areas,
in which case they are called ganglioneuroblastomas.
Prognosis in neuroblastoma is highly dependent on the age of onset of disease,
with survival rates at two years as follows: neonates (70%), cases aged under
one year (30%),
cases aged between one and two years (20%), and cases aged over two years (5%).
Tumour stage also has an important bearing on prognosis. Staging is based on
whether
tumour is confined to the adrenal, on whether it crosses the midline, on
evidence of lymph
node involvement and on evidence of bloodstream spread. An important stage of
neuroblastoma
is defined as stage 4S, in which there is a localized primary tumour with
metastasis
to skin and liver, with minimal marrow involvement; this is confined to children
under the age of
1 year. Paradoxically, stage 4S is associated with a very good prognosis and
spontanous
regression of tumour with little or no treatment.
The natural history of untreated neuroblastoma is for local and metastatic
spread resulting
in death. With treatment, many tumours show partial or complete response to
therapy. |
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