AIMS: This study was undertaken to compare the histopathological, immunohistochemical and ultrastructural features of the so-called giant multi nucleate cells in cutaneous collagenomas: giant-cell collagenoma and solitary sclerotic fibroma. METHODS AND RESULTS: We studied four collagenomas: one giant-cell collagenoma and three solitary sclerotic fibromas. All the cases showed an indolent clinical presentation and were histologically constituted by a well-demarcated dome-shaped proliferation of coarse collagen bundles with a varying number of interspersed giant multinucleate cells and stellate mononuclear cells. The immunohistochemical study on paraffin sections revealed that neoplastic cells in both collagenomas were vimentin and CD34-positive, whereas FXIIIa was only expressed in solitary sclerotic fibromas. In regard to the so-called giant multinucleate cells, we have ultrastructurally found that these cells were 'real' multinucleate cells in giant-cell collagenoma, whereas in solitary sclerotic fibromas they consisted of closely packed aggregates of individual stellate mononuclear cells. Moreover, perinuclear cisternae focally containing finely textured material of moderate density were unexpectedly found in giant cells of giant-cell collagenoma, a finding which was not observed in solitary sclerotic fibromas. Additionally, a characteristic cell-cell interaction between tumour cells and mast cells was encountered in all collagenomas. CONCLUSIONS: This study supports a distinctive immunohistochemical and overall ultrastructural profile of giant multinucleate cells in giant-cell collagenoma and solitary sclerotic fibroma, which suggests a different pattern of differentiation for these two related cutaneous lesions.
AIMS: This study was undertaken to compare the histopathological, immunohistochemical and ultrastructural features of the so-called giant multi nucleate cells in cutaneous collagenomas: giant-cell collagenoma and solitary sclerotic fibroma. METHODS AND RESULTS: We studied four collagenomas: one giant-cell collagenoma and three solitary sclerotic fibromas. All the cases showed an indolent clinical presentation and were histologically constituted by a well-demarcated dome-shaped proliferation of coarse collagen bundles with a varying number of interspersed giant multinucleate cells and stellate mononuclear cells. The immunohistochemical study on paraffin sections revealed that neoplastic cells in both collagenomas were vimentin and CD34-positive, whereas FXIIIa was only expressed in solitary sclerotic fibromas. In regard to the so-called giant multinucleate cells, we have ultrastructurally found that these cells were 'real' multinucleate cells in giant-cell collagenoma, whereas in solitary sclerotic fibromas they consisted of closely packed aggregates of individual stellate mononuclear cells. Moreover, perinuclear cisternae focally containing finely textured material of moderate density were unexpectedly found in giant cells of giant-cell collagenoma, a finding which was not observed in solitary sclerotic fibromas. Additionally, a characteristic cell-cell interaction between tumour cells and mast cells was encountered in all collagenomas. CONCLUSIONS: This study supports a distinctive immunohistochemical and overall ultrastructural profile of giant multinucleate cells in giant-cell collagenoma and solitary sclerotic fibroma, which suggests a different pattern of differentiation for these two related cutaneous lesions.