Necrosis is uncommon in adenocarcinomas, however, large tumors may show central necrosis and cavitation. Most adenocarcinomas are between 2 and 5 cm at the time of resection. Over half of patients who present with adenocarcinoma are detected by an asymptomatic nodule on a routine chest radiograph. The cut surface is often white to pale gray with black anthracotic pigment and glistens if mucin is present. Desmoplastic reactions are often associated with adenocarcinomas and give the tumor a firm fibrous consistency.
Adenocarcinomas tend to be well circumscribed and contain central necrotic cores.
Less commonly they from cavitary lesions. Adenocarcinomas are also associated with subpleural scars due to a variety of causes, including old infarcts, healed pneumonitis or granulomas, or trauma. However, others have suggested different groupings. Demonstration of mucin is essential when differentiating the solid variant from a large cell carcinoma of the lung, which by definition stains negatively for mucin. Adenocarcinomas are also subclassified based upon their degree of differentiation into well, moderate and poorly differentiated forms.