Fibrous tumors

Chapter 20


Fibrous tumors



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Many additional entities are included in the on-line atlas of fibrous and soft tissue tumors that accompanies this book.



Dermatofibroma



All dermatofibromas demonstrate a proliferation of fibrohistiocytic cells. A curlicue pattern is typical. Another typical feature is that some areas of the tumor will be densely cellular, while others are sclerotic and hypocellular. The overlying epidermis is acanthotic and often demonstrates primitive follicular germs or sebaceous follicles. At the periphery of the tumor, collagen trapping (collagen balls) can be seen. The tumor may extend into the superficial fat in a lacy pattern.


When present, ringed lipidized siderophages are pathognomonic for dermatofibroma. These cells are like Touton giant cells with hemosiderin. They have central pink cytoplasm surrounded by a wreath of nuclei. There is both lipid and hemosiderin peripheral to the ring of nuclei.


Immunostaining can be helpful to separate cellular dermatofibromas from dermatofibrosarcoma protuberans. Large stellate cells within a dermatofibroma stain for factor XIIIa. The surrounding stroma will stain for CD34, but the central tumor is negative (except for endothelial cells).














Apr 26, 2016 | Posted by in Dermatology | Comments Off on Fibrous tumors
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