Recent diagnosis w/autoimmune disease & skin biopsy result: urticaria or mast cell disease. shouldn't biopsy give more definitive diagnosis?

Biopsy: Pathologists describe the type of cells they see and suggest a compatible diagnosis but cannot give a definitive dianosis themselves. You may have urticarial vasculitis. Mastocytosis will need to be ruled out based on the pathology findings too.

Hard to tell: Mast cells are the cells that release histamine in the body. This is what happens in urticaria, so one will see mast cells in biopsies of urticarial (hive-like) lesions. Mast cells can also be found in increased numbers in people with mastocytosis. Thus the biopsies may be similar. As stated by my colleague, the clinical history can be key to the diagnosis. Talk with your doc.