P36.01 Primary Acinic Cell Carcinoma of Bronchial Ground Origin: A Case Report

Abstract

Primary acinic cell carcinoma of the lung is an extremely rare disease. Also known as Fechner’s tumor, this condition was first reported by Fechner et al. in 1972. The accurate diagnosis of primary pulmonary acinic cell carcinoma is difficult and relies on comprehensive evaluation of clinical, histological and immunohistochemical features. A 49-year-old male patient was referred to our hospital because of an abnormal infiltration shadow in the left lower lung field detected on a chest radiograph during a medical check-up. Chest computed tomography revealed a nodal mass shadow 10mm in size, in segment 8 of the left lower lobe. Bronchoscopic examination revealed a polypoid tumor at B8. Transbronchial biopsy was performed and the tumor was diagnosed as a bronchial gland adenoma. The patient underwent video-assisted thoracic segmentectomy to achieve complete resection of the tumor. Macroscopically, the tumor was a solitary mass measuring 14×10×8 mm in size with substantial cut surface and showed no intraparenchimal growth. Histopathological examination revealed a polypoid projection in the bronchial space. Adeno-type cancer cells with monomorphous nuclei invade the bronchial wall tissue in association with tubule or acinus-like space formation. The cytoplasm of the tumor cells is plump and eosinophilic with granularity or clear. No direct invasion into the lung parenchyma was observed. Immunohistochemical staining revealed that the tumor cells were positive for PAS, lactoferrin, and HMG-45MI. The features are consistent with acinic cell carcinoma of bronchial gland origin. Electron microscopy showed that the acinus-forming tumor cell possess well-developed mitochondria and round-surfaced endoplasmic reticulum, in association with active luminal secretion. Rounded, electron-dense secretory exocrine granules, ranging from 150 to 340 nm in size, are noted mainly in the apical cytoplasm. Fat vacuoles are noted in some tumor cells. Microvillous intracytoplasmic lumina are occasionally noted. Bundles of intermediate filaments and desmosomal attachments are also seen. These features are consistent with acinar cell nature of the cells. Fourteen years since the surgical resection, no apparent recurrence or metastasis has been detected. We experienced an extremely rare case of primary bronchial acinic cell carcinoma diagnosed based on clinical information, histopathological features, immunogistopathological staining profile, and electron microscopy features. The limited number of reports on this type of tumor have revealed that the outcome after surgical resection is favorable due to its low-grade malignant potential. Likewise in this case, the patient remained free of recurrence for over 14 years after surgery.