Angiomatous spindle cell lipoma: Report of three cases with immunohistochemical and ultrastructural study and reappraisal of former 'pseudoangiomatous' variant.

Pseudoangiomatous spindle cell lipoma (PASCL) is a rare variant of spindle cell lipoma that is composed of spindle fibroblast-like cells and mature adipose cells, and that is further characterized by intratumoral branching spaces regarded originally to be non-vascular (hence the adjective 'pseudoangiomatous'). Reported herein are three cases of this tumor, with literature review of all six cases described previously. PASCL appears to have clinical features (age, sex, location, prognosis) similar to those of conventional spindle cell lipoma (SCL). Immunohistochemically, the spindle cells in all of the present cases were positive for CD34, as in conventional SCL. All lesions had at least mild positivity for sex steroid hormone receptors. The cells lining intratumoral dilated and branching spaces typical of this variant were strongly positive for lymphatic endothelial marker D2-40 in all cases, and for vascular markers CD31 and F-VIII in one case. Ultrastructural study confirmed the endothelial nature of these cells. The results indicate that pseudoangiomatous SCL is truly angiomatous and should be termed as such. It could represent a sex steroid hormone-dependent lesion.