Alveolar adenoma is a rare lung neoplasm and few cases have been reported in literature. Such lesions are considered as benign neoplasm and no recurrences have been described. These neoplasms are usually located peripherally in the lung and their PET activities are unknown.
We report the first case of alveolar adenoma positive on PET scan, deeply located in left lower lobe.
Case presentation
A 54-year-old, non-smoker woman presented to her primary care physician for chronic, non-productive cough and mild dyspnoea. Her past medical history included partial gastrectomy for gastric ulcer, colecystectomy, dyslipidemia and gastric reflux disease. She also reported a previous occupational exposure to benzene.
Clinical examination was unremarkable and pulmonary function was normal. The chest X-ray and the subsequent enhanced chest computed tomography (CT) scan revealed the presence of a well-circumscribed, ovular, smooth edged, dense pulmonary lesion in the left inferior hilum (Figure 1). The diameter of the nodule was approximately 18 mm, with no contrast enhancement. No other significant abnormalities were detected, in particular there was neither pleural effusion nor mediastinal adenopathy. The patient underwent a fluorine-18-fluorodeoxyglucose Positron Emission Tomography (PET) scan, revealing minor uptake in the left lower lobe nodule with a Standardized Uptake Value of 1.06. The brain and the abdomen CT scans were negative for metastatic localizations.
In order to exclude a malignancy, a fibreoptic bronchoscopy with bronchial washing and a percutaneous CT-guided fine needle aspiration biopsy were performed. Both the examinations resulted negative for malignant disease.
Notwithstanding the negative results of the cytological investigations, the PET finding and the contiguity to the hilar structures convinced the authors to remove the pulmonary nodule. Therefore, a minimally invasive muscle-sparing lateral thoracotomy was performed in order to biopsy the pulmonary lesion. The intraoperative histological examination by frozen section suggested a cystic, well-delineated lesion without sign of malignant disease; however, the finding had to be confirmed by the definitive histology obtained by paraffin block.
Considering the nodule localization (inseparable from the inferior pulmonary vein) and the intraoperative histological finding, we decided for a left lower lobectomy. The surgical procedure and the postoperative course were uneventful. The patient has been discharged 5 days after the operation in good clinical condition; after one year, she is in good health and the chest CT scan doesn't reveal any sign of recurrence.
The resected lung segment contained a well-defined yellowish, round mass, with a diameter of approximately 2 cm, with a tight adhesion to the wall of the adjacent left inferior vein.
Histologically, the mass was well demarcated (Figure 2a) and composed of a network of cystic spaces lined with simple epithelial cuboidal type II pneumocytes cells without atypia that contain stroma ranging from thin inconspicuous strands of connective tissue to broad spectrum of spindle cells sometimes in a myxoid matrix (Figure 2b). Neither mitotic figures nor necrosis were detectable. The immunohistochemical profile in the epithelial component was positive for thyroid transcription factor (TTF-1) (Figure 2c) and negative for myogenin, surfactant and cytokeratins. The mesenchimal spindle cells components were unreactive for CD34, CD68 and desmin. The proliferative activity was assessed by Ki-67 and was unremarkable in both cell types.
Due to the morphological apparence and immunohistochemical findings of the lesion the final diagnosis was alveolar adenoma of the lung.