T staging the partial ground glass nodule
Distinguishing adenocarcinoma in situ from invasive adenocarcinoma has been a topic of discussion within the lung pathology community since the mid-1990’s (1). The fundamental observation at that time was that certain histologic features of small lung adenocarcinomas predicted metastatic potential. Some small peripheral adenocarcinomas completely retain an essentially normal alveolar architecture with no evidence for stromal modification. These tumors have no metastatic potential and are relatively easily recognized as adenocarcinoma in situ. Tumors with this pure form are relatively rare. Others small carcinomas, the commonest group, show at least some obvious desmoplastic fibroblastic response, have clearly established metastatic potential and are readily recognized as invasive adenocarcinomas. The third and most problematic group are those small lung adenocarcinomas associated with bland fibroelastotic stroma that expands alveoli but whose histology is otherwise similar to normal un...