A 60 year-old male with multiple peripheral lung nodules undergoes lung biopsy. A representative section is shown here.

Unknown 20

What is the diagnosis?

A. Squamous cell carcinoma
B. Papillary adenocarcinoma
C. Adenocarcinoma in situ
D. Small cell carcinoma
E. Large cell carcinoma





(Scroll down for the answer)







The diagnosis in this case is adenocarcinoma in situ (which used to be called bronchioloalveolar carcinoma). This type of lung cancer usually occurs in the peripheral portions of the lung. It often takes the form of multiple, diffuse nodules which may give the appearance of a pneumonia-like consolidation on chest xray and even on gross examination.

Microscopically, the tumor cells grow along alveolar septae without invasion into surrounding tissue or blood vessels. As you might expect from the name, the prognosis is better for adenocarcinoma in situ than it is for other types of lung carcinoma, particularly in cases which present as a single nodule.

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