Case Number : Case 1392- 23 October Posted By: Guest

Thinking of ? Plexiform fibrohistiocytic tumor

Rhabdomyoma ?? rhabdomyomatous mesenchymal hamartoma ??

Infiltrative neoplasm with predominant fascicular pattern. Large round/ oval/ spindle cells with abundant brightly eosinophilic cytoplasm resembling rhabdomyoblasts with vesicular nuclei without significant atypia and mitotic figures. Sparse neutrophils are also seen. Young age and multiple lesions concentrated at one anatomic region are also typical of pseudomyogenic hemangioendothelioma, to IHC confirmation.

Good suggestion Romualdo :-)
Today I am learning from you :-)

Another great case from Arti who I am sure can give the answer in due course.

nice ,,, I liked Romualdo 's Idea

Romualdo's description and diagnosis is spot on! Pretty impressive that you can diagnose this (rather rare) entity on a few images, when it took me quite some time (and many immunos) to crack it, along with the help of my soft tissue colleagues.
Plexiform fibrohistiocytic tumour is very good differential, which we considered as well, however multinucleate cells were lacking and the immunos did not fit.
The clue to the diagnosis of pseudomyogenic haemangioendothlioma lies in the 'rhabdomyoblast like cells' (which also give its name), well demonstrated in the last 2 images.
Immunos confirmed the endothelial nature of the tumour (CD 31 and ERG positive). Desmin, myoD1, myogenin were negative. The tumor is expected to show diffuse cytokeratin positivity but this was disappointing in this case. We tried quite a few cytokeratins and there was only patchy positivity with AE1/3. There was no loss of INI1. The clinical presentation is typical with multicentric spread.
Thanks to Richard for sharing this case on dermpathpro and thank you all for you comments!