Thanks for visiting HCM.
Inhomogenous opacity on chest x-ray in an elderly heavy smoker must be considered a malignant or cancerous mass unless proved otherwise by investigations. Other possibilities can be tuberculosis
, bacterial infections, collapse etc. Pleural based triangular opacity can be pleural effusion
i.e is collection of pleural fluid between the two pleural layers, plural thickening, pleural spread of cancer etc.
can be asymptomatic till it is widely spread...
I think you must go for computed tomography
scan of thorax (CT Thorax) of your father to get cleared about the nature of the lesion and if it is suggestive of cancerous then in the same sitting CT guided biopsy can be taken and subjected to histopathological examination for confirmation. Similarly pleural fluid can be aspirated and sent for routine microscopy, adenosine de-aminase, acid fast bacilli, culture and sensitivity. Further treatment will be guided by laboratory reports.
Consult a pulmonologist
for thorough evaluation and treatment...
Best wishes for your father's health.