Atypical carcinoid of the lung: radiographic features.

Atypical carcinoid of the lung is a neuroendocrine neoplasm with cellular and clinical features intermediate between those of typical carcinoid and small cell undifferentiated carcinoma of the lung. These neoplasms exhibit a wide range of histologic appearances and are misdiagnosed in up to 50% of cases. The clinical records and radiographs of 32 patients with this diagnosis from the University of Virginia Medical Center and Wake Forest University Medical Center were reviewed. Sixteen of these cases had been misdiagnosed pathologically. While the most frequent radiographic finding was a round or avoid lobulated peripheral mass, other appearances included thin-walled cavities, poorly defined nonsegmental infiltrates, and mediastinal masses. Fifty percent of the patients in this study have died from their tumor, with a mean survival of 15.5 months. This contrasts with both typical carcinoid and small cell undifferentiated carcinoma, in which patients develop fatal metastatic disease in 5% and nearly 100%, respectively. Proper categorization of typical carcinoid, atypical carcinoid, and small cell undifferentiated carcinoma is necessary to determine appropriate therapy, prognosis, and reporting of end results.