Lines of cell differentiation in solitary fibrous tumor: an ultrastructural and immunohistochemical study of 10 cases.

BACKGROUND

Solitary fibrous tumor (SFT) is a rare ubiquitous mesenchymal neoplasm of probable fibroblastic type with a prominent hemangiopericytoma-like vascular pattern. Since their initial description as arising from the pleura, SFTs have been reported in many extraserosal sites. It is now accepted that this neoplasm is derived from mesenchymal cells but its histogenesis is still not known.

METHODS

The authors gathered clinical data on 10 patients with SFT. Tissue microarrays were constructed to perform inmunohistochemical tests and we reviewed hematoxilin-eosin-stained slides. Electron-microscopically collected samples were fixed with formalin or Karnovsky reactive and embedded in epoxy resin.

RESULTS

The histopathological review showed varying degrees of cell density and mitotic activity, which correlated with clinical behavior. Immunohistochemically most tumors stained positively for vimentin, CD99, and CD34. Ultrastructural study showed some degree of myofibroblastic differentiation in all cases and focal smooth muscle features. In addition, 9 cases showed perivascular undifferentiated cells.

CONCLUSION

SFT is an uncommon neoplasm with different histological patterns and clinical behavior. The authors hypothesize that the perivascular undifferentiated cells that most cases showed might correspond to a quiescent stage of adult stem mesenchymal cell and could be the target of the molecular aberrations implied in its pathogenesis.