If you have a case like this and are in doubt about sclerosing rhabdo versus alveolar, just do the RT-PCR for t(1;13) and t(2;13) (the characteristic translocations of alveolar rhabdo). Alveolar has a fairly poor prognosis. Sclerosing is relatively new and I am not sure if we really understand the prognosis well based on the limited number of described cases.

I have also interpreted that case as alv. rhabdo., but actually it does have a microalveolar pattern, and not large alveolar areas. Great information. Thanks for sharing.

Viral, Yes, it does have a microalveolar pattern. See my comment below for further explanation.

at first impression seems to Alveolar RMS

Thanks for the complement :) and waiting for your new collection.

This tumor actually has a "microalveolar" pattern...that is, small alveolar structures, as opposed to the large alveolar areas and intervening fibrous septa containing blood vessels that characterize alveolar rhabdomyosarcoma (I don't have a scanned slide uploaded yet. Here is a pic from google to show you: http://www.pedorthpath.com/alveolar_rhabdomyosarcoma_histo_1.jpg). When sclerosing rhabdomyosarcoma was first described (my mentor, Sharon Weiss, was one of the first to describe it, along with Andrew Folpe), some investigators thought it might actually be related to alveolar rhabdomyosarcoma. However, subsequent studies have shown that sclerosing rhabdo is NOT positive for the 1:13 and 2:13 translocations that define alveolar rhabdo (to my knowledge, at least). Some actually think sclerosing rhabdo may be a subtype of embryonal, but that has not been proven yet. Sadiq, I am really glad you have been working so hard at looking at my cases. Keep up the great work, and you will be a soft tissue pathologist in no time!

Thanks for sharing you interesting cases. I notice that about 30-40% of the tumor in this slide shows an alveolar pattern of growth. So why you favor the diagnosis of sclerosing vs alveolar variant of rhabdomyosarcoma? Thanks again