部位は頭皮の皮下で、境界明瞭な結節状の腫瘍性病変です。 紡錘形の腫瘍細胞の束状増殖と、スリット状の血管腔形成がみられること から血管性腫瘍を考えました。

I follow the context in the BBS.The previous accessment about this challenge let me learn a lot. Another possibility come to me is "epitheloid hemangiendothelioma". I used to review the spindle cell hemagioendothelioma (recently revised as spindle cell hemangioma due to benign clinical course) which had carvernous-like vascular space in the tumor's mainpart. This challenge does not reveal the pattern. But I still appreciate the possibility of intravascular fasciitis. In conclusion: 1. intravascular fasciitis >2. epitheloid HE >3. myofibroma (biphasic pattern?)

Because of its round conture outlined by fibrous tissues and extensive red cell spillage within the tumor, it seems to be a rare intravascular variant of nodular fasciitis. Spindle cell hemangioma appears unlikely, because of the lack of malformed cavernous blood vessels and collapsed vasculature consisting of plump endothelial cells and interposed pericytic spindle cells. Alternatively, it may be possble that the vascular tumor occupied a malformed cavernous vascular space. Kaposiform HE and Kaposi sarcoma, though their histology partially resembles the present case, do not fit in its noninvasive round shape and subcutaneous location. The presence of vacuolar cells and poor luminal formation may suggest epithelioid HE, but the tumor cells are spindled and there is no myxohyaline stroma. Perivascular myoma including myopericytoma and myofibroma is difficult to realize as neither perithelial arrangement nor biphasic differentiation is recognized, Instead, cellular vascular leiomyoma remains in consideration. Special staining is required for differentiation.