Many symptoms of LAM are similar to those of more common lung diseases such as asthma and for this reason patients may have symptoms for a long period before LAM is diagnosed correctly. Symptoms, X-rays and breathing (lung function) tests may suggest LAM but the diagnosis is usually confirmed by a CT scan (a detailed X-ray scan) of the lungs and sometimes with a lung biopsy. In a patient with LAM the CT scan usually shows typical cysts throughout the lungs. A lung biopsy may be performed in some cases where the doctor feels more information is needed to ensure that the diagnosis is correct. This is usually carried out through a fairly small incision in the chest under a general anesthetic. In LAM the biopsy will show the typical cysts and smooth muscle cells. The kidney tumours are also seen best on a CT scan although they can also be seen with ultrasound.