Can a pituitary gland tumor misdiagnosed with depression?

pituitary tumor. Any tumor or lesion in brain may develop symptoms of depression. It is not a misdiagnosis, if your doctor just found you have depression. It should be a incomplete diagnosis. Depression is just a common symptom, not a exact etiology.
Sometimes. A pituitary tumor may lead to severe weakness with depression. But you will be fine a tumor of this kind is treatable and most often curable.