| This
slow growing locally aggressive adnexal tumour was first reported by
Goldstein et al, in 1982. This tumour shows both eccrine and
pilar differentiation. However, it has been recently regarded as an apocrine tumour.
Clinical presentation:
The tumour usually
presents as skin coloured indurated plaque or nodule.
Site:
The lesion occurs
usually on the upper lip or elsewhere on the face. This lesion may
also occur in the axilla, extremities, genital skin, trunk and scalp.
Microscopic
features: Low power view:
Image1 ; Image2 ;
Image3
. High power view:
Image4; Image5 ;
Image6
;Image7
.
CASE LINK:
Microscopically this infiltrating tumour involves the dermis, subcutis
and may also extend into the underlying muscle.
The superficial part is composed of numerous keratinous cysts.
Solid islands and strands of basaloid and squamous cells alternate
with the cysts. These cells may show ductal differentiation. Focal
microcalcification, clear cell changes, prominent lumina and
arborizing tubules may be present.
In the mid dermis, the basaloid strand and ducts are prominent but the
keratinous cysts are diminished in number. Focally sebaceous and
follicular differentiation may be seen.
The deeper component has a schirrous appearance and shows smaller
nests and strands of cells in a dense hyalinized stroma.The epithelial
elements are diminished to small clusters of 2 or 3 cells.
Cytologically the tumour cells are of uniform size. Mitotic figures
are rarely seen.
Prominent glandular component may be present (known as sclerosing
sweat duct carcinoma or malignant syringoma).
Immunohistochemistry:EMA positive cells:
Immunohistochemically the luminal cells express CEA. The tumour cells
also stain for EMA and various cytokeratins (particularly CK7). Some
S100 positive cells are present, but the stroma is CD34 negative. (D/D:In Desmoplastic trichoepithelioma the stroma
may be CD34 positive). Low level of Ki 67 indicates low proliferative
index.
Differential
Diagnosis:
Desmoplastic
trichoepithelioma,
morpheic basal cell carcinoma,
metastatic breast carcinoma,
syringoma,
papillary eccrine
adenoma.
Desmoplastic trichoepithelioma and syringoma do not show evidence of
aggressive growth pattern and perineural spread. It is not possible to
give a definitive diagnosis in shave or superficial punch biopsies.
In morpheic basal cell carcinoma there is no lumen formation or
zonation of the tumour.
Mohs micrograph surgery is the current treatment of choice.
Local recurrence occurs in 50% cases. This is less likely if excision
margins are free of tumour in the initial biopsy.
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