<s>[INST] HI Doctor, If there is malignancy in the lingual space and tongue and now there is malignant effusion in that area and into the neck, would that area be defined as pleural effusion/pleural tissue? If so, is this indicitive of the Cancer having spread to the Lung? [/INST] Thanks for your question on Chat Doctor. Malignancy of lingual and tongue is mostly squamous cell origin. And it is spread by blood. So practically affect any organ of the body. So pleural metastases can be seen in such malignant lesion. And lungs and pleura are considered different organs in cancer spread.  So malignant pleural effusion does not always suggest lung involvement.  It may or may not involve lung tissue. So one needs CT THORAX to diagnose lung metastases. </s>