TRICHOBLASTOMA HAVING SEBACEOUS DIFFERENTIATION
Primitive follicular epithelial elements, combined
with minimal specialized follicular stroma, are found within a single
nodule that is sharply delimited by a pseudocapsule. These are the
features of a trichoblastoma as described by Headington and discussed
in the context of another case.
This type of benign tumor may be restricted to the dermis, may be restricted to the subcutis, or may involve both locations. The degree of follicular differentiation varies from case to case. The epithelial elements in this example do not form subunits composed of multiple follicular elements arranged in recognizable follicular architecture. This lack of 'trichoepitheliomatous' subunits could lead to a mistaken diagnosis of basal cell carcinoma.
Sebaceous differentiation is very uncommon in this uncommon tumor.
This type of benign tumor may be restricted to the dermis, may be restricted to the subcutis, or may involve both locations. The degree of follicular differentiation varies from case to case. The epithelial elements in this example do not form subunits composed of multiple follicular elements arranged in recognizable follicular architecture. This lack of 'trichoepitheliomatous' subunits could lead to a mistaken diagnosis of basal cell carcinoma.
Sebaceous differentiation is very uncommon in this uncommon tumor.
This subcutaneous tumor was easily shelled out of a
lower extremity of an adult. It measured 27 millimeters in greatest
dimension.
David Bolick provided the glass slide for this case.
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David Bolick provided the glass slide for this case.
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| Direct scan that includes most of the tumor. It is sharply circumscribed and composed of lobules of basaloid cells. |
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| This shows the interface of
the tumor and the adjacent connective tissue. The collagenous tumor
stroma in this area forms a pseudocapsule. Some of the nests of
primordial epithelium are associated with collagenous stroma and others
are associated with loose connective tissue containing scattered
fibroblasts. |
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| This shows a retiform pattern
of thin strands of basaloid cells separated by loose connective tissue
that contains scattered fibroblasts. There is occasional condensation
of the stroma against the epithelium. This is interpreted as primitive
follicular differentiation. |
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| The strands of basaloid cells
are broader in this picture, and there is decreased cytoplasmic density
centrally within some of these strands. However, this is not diagnostic
for sebaceous differentiation or outer root sheath differentiation. |
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| There are areas of
unequivocal sebaceous differentiation. The stroma in this area is
denser and more collagenous than that seen in the other pictures. |
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| Higher power view showing sebaceous differentiation. |
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