Case Number : Case 3066 - 07 April 2022 Posted By: Saleem Taibjee

Looks like cutaneous mastocytosis. special stain/IHC confirmation + work up to exclude systemic mastocytosis suggested.

Telangiectasia macularis eruptiva perstans

Yeahhh!  Totally Agree. Found this case very difficult, but last pictures show nice spindle mast cells...

Well, what can I say - you guys are so impressive. You made short work of a difficult case. I did not disclose this in the original clinical information provided, but mastocytosis was suggested in the differential diagnosis. The difficulty in this case is increased because there is spongiosis in the overlying epidermis which could lead one towards the wrong diagnosis. (such as when I first looked at the slides blind of the clinical, as is my practice). However, when I then saw the clinical differential diagnosis on the request form, I took another look at the slide, and I could then appreciate the mast cells. Of course, the accompanying eosinophils are also a clue. I think we can call this 'eczematised' mastocytosis.

Immunohistochemistry for CD117 shown below is confirmatory.