Unless you are calling an apothecium a mushroom I wouldn't worry. Some apothecium are harmless some are bad. The first negative one that comes to mind is the fruiting body of Sclerotinia Sclerotiorum.
There are some ectomycorrhizas that form fruiting bodies. A good book to have around if your interested in mycorrhiza is pictured here:
There are some ectomycorrhizas that form fruiting bodies. A good book to have around if your interested in mycorrhiza is pictured here: