Lipomatous hemangiopericytoma is a rare mesenchymal
tumor showing areas of
lipid-containing cells admixed with a spindle-cell component. Like other
hemangiopericytomas, it shows a similar vascular pattern to
solitary fibrous tumor and, partly for this reason, it and other
hemangiopericytomas have been subsumed into
solitary fibrous tumor. The present study provides a comprehensive documentation of a single case of pulmonary
lipomatous hemangiopericytoma of the lung, the first to be described at this site, and compares it with
solitary fibrous tumor, in terms of clinical, histological, immunohistochemical, ultrastructural, and cytogenetic findings. Apart from the
lipid-laden-cell component, pulmonary
lipomatous hemangiopericytoma and
solitary fibrous tumor were similar histologically. Bcl-2 was positive in both. CD34 was minimally expressed in pulmonary
lipomatous hemangiopericytoma, which possessed some non-descriptive intercellular junctions, a feature shared by
solitary fibrous tumor, which was CD34 positive. However, one of the latter was rich in gap junctions, a feature consistent with strong
connexin (Cx) 43 staining and the existence, hitherto unappreciated, of a CD34/
Cx43-positive
tumor cell network. In pulmonary
lipomatous hemangiopericytoma, chromosomal deletions of 43-44, X, -Y were found. In
solitary fibrous tumor, 46, XY, del(13)(q?) abnormalities and abnormalities involving chromosome 10 were frequently observed. These similarities and differences are discussed in the context of the currently favored diagnostic fusion of
hemangiopericytoma and
solitary fibrous tumor.