Can you have malt lymphoma with no symptoms? what are the usual symptoms?

Yes you can: Malt lymphomas are typical indolent and asymptomatic. They can involve the lymph nodes or be infiltrating an organ. Symptoms, when present, are due to local compression causing swelling or local pain if the tumor has grown to a good sized mass.

Yes but unusual: Common sites of Mucosa Associated Lymphoid Tissue (MALTOMA) lymphoma include stomach, salivary gland, skin and those areas have usually antecedent inflammatory infectious background. In stomach, Helicobacter bacteria, in parotid autoimmune and in skin may be Lyme disease. Usual stomach symptoms include ulcer or gastritis, swelling of glands in face and bumps on skin.