Lung Abscess: This is often the first consideration for a thick-walled cavity in the lung due to its common presentation as a fluid-filled cavity with an irregular, thick wall, typically resulting from an infection.

Squamous Cell Carcinoma: A common type of lung cancer that can present as a thick-walled cavity, especially if the tumor has outgrown its blood supply and undergone central necrosis.
Tuberculosis (TB): Can cause cavitation, especially in the upper lobes of the lungs, with thick walls due to chronic infection and inflammation.
Pneumonia with Cavitation: Certain types of pneumonia, such as Staphylococcus aureus or Klebsiella pneumoniae, can lead to cavitation with thick walls due to the aggressive nature of the infection.

Pulmonary Embolism with Infarction: Although less common, a pulmonary embolism can lead to infarction of lung tissue, which may cavitate and present with a thick wall. Missing this diagnosis could be fatal.
Fungal Infections (e.g., Aspergilloma): In immunocompromised patients, fungal infections can cause cavitation and must be considered to provide appropriate treatment.
Septic Emboli: These can result from bacterial endocarditis or other sources of bacteremia and can lead to multiple cavities with varying wall thicknesses.

Pulmonary Langerhans Cell Histiocytosis: A rare disease that can cause cystic and nodular changes in the lung, including cavitation.
Rheumatoid Nodules: In patients with rheumatoid arthritis, lung nodules can form and occasionally cavitate, presenting with thick walls.
Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A form of vasculitis that can affect the lungs and cause cavitation, although this is less common.