A 60 year-old male with multiple peripheral lung nodules undergoes lung biopsy. A representative section is shown here.
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.
If you liked this case, and want to test yourself with other unknown cases, here are some to try:
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The findings in your picture actually look more consistent with papillary or micropapillary pattern of adenocarcinoma. Adenocarcinoma in situ is currently defined as a solitary lesion, so it doesn’t make sense that this gentleman has multiple lesions. I think that you are thinking of the old mucinous bronchioloalveolar carcinoma (which now is known as mucinous adenocarcinoma). That lesion is often multifocal.
Thanks for your comments! This is an older case that was previously diagnosed as bronchioloalveolar carcinoma. Now that the names have changed (it seems that most cases previously designated bronchioloalveolar carcinoma are being designated adenocarcinoma in situ) some of the other clinical findings may be changing as well.
I see your point about the slide showing some possible papillary structures and the possibility of mucin within the cells. Robbins 9 (the new Robbins) says that cases of adenocarcinoma in situ (the old bronchoalveolar carcinoma) may or may not have mucin present in the dysplastic cells. It is an area that will need some clarification as the terms seem to overlap in an muddy way. I would imagine that any adenocarcinoma in situ could be mutlifocal (DCIS in the breast, for example, may be multifocal) – so not sure that’s a good way to distinguish between adenocarcinoma in situ.
I would need to send this case to someone like you who knew more than I do about the emerging classification of these lesions!