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Targetoid hemosiderotic
hemangioma is a distinctive cutaneous vascular tumour
which was described in 1988.
The histologically descriptive
term 'hobnail hemangioma' was proposed to designate these lesions.
The commonly proposed
etiology is trauma to a preexisting hemangioma. This lesion has also been
reported in pregnancy and in a father and son. Hormones may
potentiate these tumours. Some authors have suggested a lymphatic origin
for hobnail hemangiomas.
Age:
Usually presents as a single
lesion in young and middle aged individuals .
Site:
The common locations include the lower limb (particularly the thigh) and
the trunk, including the shoulder area. Other less common sites are the
head , gingiva, and the tongue
Clinical presentation:
The lesion may present
as angiomatous / pigmented, nontargetoid, flat, or exophytic lesion.
The tumour size usually ranges from 0.2 to 3cm in diameter.
Some of the tumours have a distinctive targetoid appearance
characterized by
small violaceous papule at the center surrounded by a pale area and an ecchymotic
or brown ring which expands and later disappears. The central papule
persists.
Microscopic features:
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This poorly
circumscribed vascular lesion consists of a biphasic pattern.
Superficial component :
Dilated thin walled vessels lined by plump
endothelial (hobnail) cells. Fibrin thrombi are seen within some superficial
vessels. Some vessels show endoluminal stromal papillae
formation. There is no endothelial multilayering or tufting.
Deeper component:
The vascular spaces are
smaller, slit-like and angulated in the deeper dermis. The endothelial
cells lining these vessels are less conspicuous. The vessels have a
collagen-dissecting, pseudoangiosarcomatous pattern and infiltrated
into the dermis and subcutis.
There is extravasation of red blood cells and hemosiderin pigments in
the surrounding stroma.
Cytologic atypia is
usually minimal or absent. There is no mitotic activity.
Immunohistochemistry:
There is variable reactivity of endothelial cells with CD31, CD34,
Factor VIII-related antigen
&
Ulex europaeus agglutinin-1. Smooth muscle actin-positive pericytes
are observed focally around some of the abnormal vascular spaces.
Differential Diagnosis:
Skin changes following radiation therapy ;
Dabska's tumour ;
Retiform
hemangioendothelioma ;
patch stage Kaposi's sarcoma ;
well- differentiated angiosarcoma.
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