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Malignant sweat gland tumours
are a rare and heterogeneous group of tumours. Because of their rarity
, their definition and categorization is difficult.
These are primary
cutaneous malignant tumours which show glandular/ductal formation that
is presumed to reflect differentiation toward eccrine or apocrine
ducts and/or glands.
Most benign sweat
gland tumours have a malignant counterpart (Eg. Malignant eccrine
poroma, malignant mixed tumour, hidradenocarcinoma).
An accurate
diagnosis depends on the identification of the residual benign
component.
A small number of malignant
sweat gland tumours do not have a benign counterpart and their
identification rests on recognition of distinctive histological
features (i.e Aggressive Digital Papillary Adenocarcinoma).
Diagnosis:
-
To make a diagnosis of sweat gland
carcinoma one should first establish that the tumour shows sweat
gland differentiation.
- Sweat gland
differentiation is recognized by identification of extracellular
ductal or intracytoplasmic lumen formation. This can be highlighted by
their diastase-resistant PAS, EMA and CEA positivity. Demonstration of
S100 protein may be useful pointer to sweat gland differentiation.
-
Distinction of some
types of sweat gland carcinoma from metastatic adenocarcinoma is not
possible on morphological grounds.
Immunohistochemistry except for a few cases (prostate and thyroid) does
not allow distinction between a primary malignant adnexal tumour and a
metastatic tumour. Malignant sweat gland tumour are often positive for
oestrogen and progesterone receptors and these markers are therefore
of limited usage in differential diagnosis.
-
Diagnosis of malignancy is based on a combination of histological
findings which include infiltrative growth pattern, cytological atypia,
mitotic count, necrosis and vascular and perineural invasion. Diagnosis of malignancy
should not be made
based on a single histological finding as benign tumours have frequent mitotic figures and
focal cytological atypia which is often degenerative in nature.
Classification
of malignant sweat gland tumours is necessary because:
-Different
types of tumour have different natural history and clinical behaviour.
Low grade - Locally
aggressive, but little risk of metastases.
Intermediate grade
- Locally aggressive, increasing risk of metastases.
High grade
- High risk of metastases
-Some
cases may be clearly
distinguished histologically from metastatic tumours, whereas others
cannot. |
