Collar button lesions are seen in which of the following?
Carcinoids may arise centrally or may be peripheral. On gross examination, the central tumors grow as finger-like or spherical polypoid masses that commonly project into the lumen of the bronchus and are usually covered by an intact mucosa. Most are confined to the main stem bronchi. Others, however, produce little intraluminal mass but instead penetrate the bronchial wall to fan out in the peribronchial tissue, producing the so-called collar-button lesion Ref: Robbins 8th edition Chapter 15.
Carcinoids
Adenocarcinoma
Squamous cell carcinoma
None of the above