ADENOSQUAMOUS CARCINOMA OF THE LUNG - RADIOLOGIC APPEARANCE

OBJECTIVE. To our knowledge, the imaging features of pulmonary adenosq uamous carcinoma, a form of bronchogenic carcinoma with a greater prop ensity for metastases at the time of diagnosis and a poorer prognosis than other forms of bronchogenic carcinoma, have not been reported, Ac cordingly, we studied the radiologic appearance of this tumor to descr ibe the findings and discern if there are features that distinguish it from other bronchogenic carcinomas. MATERIALS AND METHODS. Clinical a nd radiologic features of 30 cases of adenosquamous carcinoma were rev iewed. Chest radiographs were available in all cases and CT scans were available in 23. In cases without CT scans, planar tomograms were rev iewed in five cases and MR images were reviewed in one. Tumors were de fined by location, morphology, and TNM classification. RESULTS. The tu mors measured 0.6-6.5 cm in diameter (mean, 2.8 cm) on CT scans or che st radiographs. One tumor not seen even in retrospect on CT scans or c hest radiographs was found at autopsy. Twenty-five tumors were solid a nd four were cavitary, Five tumors were central and 25 were peripheral , including one tumor of the superior sulcus of the lung and the tumor not seen at imaging. Tumor margins were poorly defined in 19 and spic ulated in 10. Four large masses had heterogeneous attenuation on CT sc ans; one had punctate calcification. Fifty-three percent of tumors wer e peripheral nodules 1-3 cm in diameter, Results of fine-needle aspira tion of 18 masses indicated malignant tumors in 16 cases, but adenosqu amous carcinoma in only two. Evidence of previous lung injury, includi ng tumor in or next to scar, pneumoconiosis, radiation fibrosis, and i nterstitial fibrosis, was found on CT scans, chest radiographs, and/or pathology in half the patients. CONCLUSION. The radiologic findings o f adenosquamous lung carcinoma are a spectrum, typically a peripheral solitary nodule, less commonly a central hilar mass or tumor of the su perior sulcus. Scar or fibrosis within the lungs suggests that adenosq uamous carcinoma, just as adenocarcinoma, may arise in scarred lung pa renchyma.