There are a growing number of malignancies with characteristic molecular abnormalities that can help us make an initial diagnosis, that affect prognosis and/or can predict whether specific treatments will be efficacious. So most of the molecular evaluation that is done for clinical purposes is very targeted (i.e. FISH or PCR to find expected gene rearrangements, PCR for mutations status of specific genes/loci, immunohistochemistry to look for change in expression of protein products). Larger genome-wide studies with aCGH/SNP arrays or next gen sequencing techniques are certainly being done for research purposes (often looking for new biomarkers which could be targeted with small molecule inhibitors, among other things), but using that sort of broad evaluation hasn't been integrated into day to day clinical practice yet.
In response to your second question, yes, we certainly review other tests in making diagnoses. We regularly review imaging/endoscopic findings, operative and other clinical notes, other lab values, etc. It is very helpful, and in some instances completely necessary, to integrate clinical and pathologic findings in order to make a specific diagnosis.