Clinical trial is a combined Phase I/II imaging, open label, single site study in patients with known or suspected carcinoma of the lung, breast, renal cell, pancreas or brain, and with gastrointestinal malignancies, neuroendocrine tumours, or lymphoma. One 18F-FLT PET scan will be performed in 10 Phase I patients, and pre-injection and post-imaging blood work and vital signs will be collected. Up to 5 18F-FLT PET scans will be performed in 170 Phase II patients.