Carcinoid : Gross
About two-thirds of lung carcinoids are located centrally near major airways such as main stem or lobar bronchi. The remaining one-third are peripheral, not associated with a bronchus, and may be asymptomatic. Peripheral tumors are more likely to be atypical carcinoids and often show spindle cell pattern. Centrally located tumors may cause obstructive pneumonia, abscesses, and bronchiectasis. Rare cases present with paraneoplastic manifestations such as Cushing syndrome, acromegaly, and Carcinoid syndrome. Grossly, carcinoids are usually well-circumscribed (as seen here), round to oval masses filling up the bronchial lumen. They may be sessile or pedunculated. An endobronchial component is seen in about half of typical carcinoids and one-third of atypical carcinoids. The overlying bronchial mucosa is usually intact. They may infiltrate the bronchial wall and extend into the surrounding lung parenchyma. The cut-surface is yellow-gray and may show fibrous septa.