Pathology of Lipomatous Hemangiopericytoma
(Fat forming solitary fibrous tumor)
hemangiopericytoma, a rare soft tissue tumour with unpredictable biologic
behavior, was reported in 1995 by Nielsen et al.
The tumour shows clinical, pathologic, immunohistochemical, and ultrastructural features of a solitary fibrous tumour and probably represent, in most cases, a fat-containing variant of solitary fibrous tumour.
Usually occurs in middle-aged patients. (mean age 54 years)
The locations included the sinonasal area, orbit , neck, mediastinum, epicardium, soft tissue of the shoulder and the retroperitoneum, right iliac fossa ,upper and lower extremity.
The tumour usually ranges in size from 4 to 10 cm in greatest diameter.
Macroscopically, it is a solid mass with a tan to yellow cut surface.
The tumour has a relatively sharp border and is composed of a variable admixture of benign lipomatous and hemangiopericytomatous components.
The hemangiopericytomatous component included oval to round cells surrounding a sinusoidal and staghorn vasculature often with perivascular hyalinization.
Mature fat varied in amount but usually occupied approximately one quarter to three quarters of the area of tumour.
The mitotic activity usually ranged from 1 to 3 mitoses per 10 high-power fields (HPF).
In one case, many multivacuolated adipocytes of variable size with characteristic nuclear scalloping (lipoblast-like cells) are present.
The tumour stained with antibodies to vimentin and not to alpha-smooth-muscle actin, muscle-specific actin, desmin, S-100 protein, glial fibrillary acidic protein, epithelial membrane antigen or keratin.
Differential diagnosis :
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