Acinic cell carcinoma of the lung ("Fechner tumor"). A clinicopathologic, immunohistochemical, and ultrastructural study of five cases.

The clinical, pathological, immunohistochemical, and ultrastructural features in five cases of primary acinic cell carcinoma of the lung are presented. The patients' ages ranged from 44 to 75 years (mean, 56); four were women and one a man. The lesions were discovered incidentally on routine chest x-ray and ranged from 1.2 to 4 cm in greatest diameter. Three tumors were located in the right middle lobe, one in the right upper lobe, and one in the left upper lobe. In three cases, the lesions presented as asymptomatic subpleural nodules in proximity to secondary bronchi, one case presented as an endobronchial tumor that led to obstructive symptoms, and one case as a well-circumscribed deep parenchymal nodule. Histologically, the tumors were composed of clear cells with abundant granular cytoplasm growing as solid sheets with focal acinar, microcystic, and papillocystic areas. Immunohistochemical stains showed strong positivity of the tumor cells for low-molecular-weight cytokeratins and epithelial membrane antigen (EMA). Focal weak cytoplasmic positivity was observed in three cases with alpha-1-antichymotrypsin and in one case with amylase. Stains for vimentin, S-100 protein, chromogranin, and lysozyme were negative in all cases examined. Electron microscopy performed in four cases showed abundant zymogen-type cytoplasmic granules of variable electron density characteristic of acinar-type secretory cells. All patients were treated by lobectomy alone. Follow-up of 3 to 10 years in four cases revealed that all patients were alive and well, with no evidence of recurrence or metastases. Because of their relatively indolent behavior and favorable prognosis, primary acinic cell carcinoma of the lung must be distinguished from other primary and metastatic clear cell tumors of the lung.