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Histopathology Image1 of Adrenal Phaeochromocytoma
Histopathology Image2 of Adrenal Phaeochromocytoma
Paragangliomas are of two types, sympathetic and parasympathetic,
depending on the type of paraganglion in which they arise.
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Extraadrenal Paraganglioma
The term phaeochromocytoma is reserved for tumors arising in the adrenal
medulla. These tumours are usually fairly easy to diagnose. However,
several areas are the subject of debate, including the identification of
malignant potential, the diagnosis of medullary hyperplasia, and the
recognition of composite tumors. Some histologic features can cause
problems in differential diagnosis. Paragangliomas may have spindle cell
morphology or contain pigment, requiring distinction from mesenchymal
tumors and melanoma, respectively. Extensive degenerative change in
pheochromocytomas may mimic adrenal cortical tumours.
In a typical adrenal phaeochromocytoma there is a packeted arrangement of short spindle cells
surrounded by vascular stroma.
Immunohistochemistry would show two cells
type -sustentacular cells and chief cells.
Electron
microscopy shows dense core neurosecretory granules. In these, noradrenaline gives a characteristic appearance of eccentrically-placed dense
cores looking like a fried egg.
The incidence of
malignancy in adrenal phaeochromocytoma has been reported as 1-14% but it
is probably truly nearer the 1% end of range due to selective reporting of
malignant cases and the inclusion in some series of extra-adrenal cases
which are widely recognized as having a higher incidence of malignancy.
Short of the
documentation of metastases, prediction of malignancy is notoriously
difficult.
General features
more likely to be associated with malignancy include large tumor size
(average 759g versus 157g for benign tumours).
Most malignant
examples are functionally active and there is a male predominance.
Histological
features more likely to be associated with malignancy include : composition
of small cells, extensive confluent necrosis, spindle cell formation (one
study only), extensive local or vascular invasion, high mitotic count
more than 3 per 30 hpf, coarse nodularity and the absence of hyaline globules and
of cells with ganglion-like features.
In one statistical
model (Linnoila et al. 1990):
- 71% of malignant paragangliomas had 2 or 3
of the features - extra-adrenal location, coarse nodularity, confluent necrosis and
absence of hyaline globules, while
- 89% of benign ones had one or none of
these features .There was a
greater than 95% probability that more than 70% of the tumors could be
correctly classified.
Special techniques
have limited value in predicting malignancy.
There is
diminished expression of neuropeptides. DNA flow cytometry suggests some
evidence that DNA aneuploid tumours are more likely to be malignant.
p53 mutations have
been found in both benign and malignant phaeochromocytomas.
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