Mass density can be encountered in lung cancer, benign tumors, sarcoma, lymphoma, Wegener's and blastomycosis and tuberculoma.

Radiological criteria for a mass lesion are chest lateral and  PA views.

Note  in a gross cut section a mass which is well demarcated from the adjacent normal lung. Malignant tumors have infiltrating edges, while benign tumors are rounded and well circumscribed.