Giant-cell fibroblastoma: a case report emphasising the presence of hyperplastic subplasmalemmal linear densities in continuity with granular matrices in the extracellular space.

Abstract

The histological, immunohistochemical and ultrastructural features of a case of giant-cell fibroblastoma from the soft tissues of the chest wall in a 48-year-old female are described with special reference to the cell surface and matrix. Subplasmalemmal linear densities (SLDs) characterised cell surfaces, and exhibited excessive development of the dense external component: foci of identical dense material were present in the matrix. The nature of these dense foci, both the external component of the SLD and those free in the extracellular space, was investigated by light microscope immunostaining for fibronectin, laminin and collagen IV. All three proteins stained vessels. There was weaker but positive staining for tumour cell surfaces and matrix, consistent with the widely dispersed nature of the dense foci. Given their fine structural appearance, these dense foci can be referred to as granular matrices. Given also that the matrix protein immunostaining pattern is consistent with the distribution of these granular matrices as observed by electron microscopy, they may be provisionally interpreted as a kind of basement-membrane-related granular matrix. The presence of these proteins emphasises the point that, while giant-cell fibroblastoma fibroblasts lack a lamina, they nevertheless bear basement-membrane-related proteins organised, however, in a non-laminate fashion. The observations reinforce the need to qualify immunostaining results by ultrastructural investigation in order to understand the organisation of immuno-detected proteins and are discussed in terms of their diagnostic and possible biological significance.