Sherman Hemsley Died from Lung Cancer

Sherman Hemsley -- the actor famous for playing George Jefferson on "The Jeffersons" -- died as a result of a cancerous mass on his lung ... this according to the El Paso County Texas Medical Examiner.

According to the Postmortem Report, obtained by TMZ, the primary cause of death is listed as "superior vena cava syndrome" -- a complication resulting from a mass on Sherman's lung.

According to the report, Sherman had been advised to get chemo and radiation therapy before he succumbed to his illness. It's unclear if Sherman was a smoker.

TMZ broke the story ... Sherman was found dead last month in his El Paso, TX home at the age of 74.