These tumours have been
divided into 2 groups : Ocular & Extraocular.
Sebaceous carcinoma is an aggressive tumour with both local recurrence
and distant metastasis.
It has been noted
that this lesion commonly occurs in the Asian population. Sebaceous
carcinoma is rarely associated with Muir-Torre syndrome.
Ocular sebaceous
carcinoma is more common. Ocular cases may mimic chalazion. The
tumour arises from the glands in the periocular region (Meibomian
glands, Glands of Zeis).
Extraocular
sebaceous carcinoma is usually noted in the head and neck area.
Grossly, the tumour
presents as nodules, papules and plaques.
Microscopic features:
Image 1
;
Image2
;
Image3
;
Image4
.
Image link
Histology reveals irregular lobular growth pattern composed of
sebaceous and undifferentiated cells .
These cells show variation in the shape and size of nuclei.
The undifferentiated cells show eosinophilic cytoplasm with fine lipid
globules.
Some large lobules show areas of atypical keratinizing cells. There is
pagetoid spread of malignant cells in the conjunctival epithelium or
epidermis of the skin of the lid. (D/D-
Extramammary Paget's disease).
This is rarely seen in extraocular sebaceous carcinoma.
The pagetoid cells contain no mucopolysaccharides but stain positively
for fat with oil red O .
[NOTE:
Identification of pagetoid growth pattern in biopsy material is
essential to recognize the presence of an underlying sebaceous
carcinoma. ]
Special stains:
To highlight the presence of tumour cells with sebaceous
differentiation one would require special histochemical techniques,
such as oil red O(Image),
Sudan IV stains on fresh tissue and EMA immunostains on paraffin
embedded tissue.
Differential diagnosis:
Squamous cell
carcinoma ; Basal cell carcinoma with sebaceous differentiation.
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