This case report suggests that the attenuation of factor XIII may induce stromal instability leading to the formation of blood-filled spaces in aneurysmal fibrous histiocytoma.
May link factor XIII attenuation to stromal instability in aneurysmal fibrous histiocytoma; hypothesis-generating case observation requiring validation.
A 39-year-old woman visited us because of a subcutaneous induration on her forehead of 7 months' duration. The tumor was tender, firm, and colored blue-black. Microscopically, the tumor was composed of fibroblastic and histiocytic cells showing no atypicality. In some part intra- or extracellular haemosiderin was diffusely seen. There were some blood-filled spaces of varying size without endothelial lining. From these findings, this case was diagnosed as aneurysmal fibrous histiocytoma (AFH), a variant form of dermatofibroma. Immunohistochemical analysis showed that factor XIIIa-positive histiocytic cells were distributed in the area without haemosiderin, but such cells were absent in the area with its deposition. Furthermore, the cells near the blood-filled space showed transition from factor XIIIa-positive to -negative, suggesting that the stromal instability induced by the attenuation of factor XIII may lead the formation of the blood-filled spaces in AFH.
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Inui et al. (2002) studied this question.
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