Minute Pulmonary Meningothelial-Like Nodules Simulating Hematogenous Lung Metastasis: A Case Report
A 52-year-old man was referred to our clinic for an 11.3 mm nodule in the left lower lobe discovered on a chest CT scan. We found eleven small nodules of various sizes in both lungs, but there was no definite lymph node enlargement in the mediastinum or either hilum (). The patient had complained of a persistent cough and mild dyspnea for several months. He had a history of secondary erythrocytosis, and was a current smoker with a history of 30 pack-years. He had no family history of cancer. His secondary erythrocytosis was mild, and he did not take any medication for it. His hemoglobin level was 18.2 g/dL, and the rest of the laboratory data revealed no abnormal results.\nInitially, we decided to perform a biopsy, and consulted with the chest radiologist to perform a transthoracic needle aspiration using CT scan guidance. The pathologic report showed a few clusters of atypical cells that were suspicious for malignancy. However, cells acquired during needle aspiration were scant, so we could not make a definite diagnosis. For further evaluation, we carried out a positron emission tomography (PET) scan, esophagogastricduodenoscopy (EGD), and colonoscopy. There was no evidence of malignancy on the EGD or colonoscopy. The PET images showed multiple lung nodules scattered in both lungs. The largest one was 11.3 mm in the left lower lobe and did not have any discernible fludeoxyglucose uptake (). We could not rule out the possibility of hematogenous lung metastasis from an unknown primary lesion.\nFor pathologic confirmation, video-assisted thoracoscopic surgery (VATS) was performed while excising a lung parenchyma sample of 3.5×1×0.6 cm. Analysis revealed a relatively well-circumscribed gray-white solid mass, measuring 1.1 cm in diameter. Microscopically, the surgical lung biopsy specimen showed an interstitial proliferation of cytologically bland oval to blunted spindle cells. The cells enveloped the small blood vessels, and seemed to form whorls with dispersed nuclear chromatin (). Immunohistochemical analysis was performed, and the sample was positive for epithelial membrane antigen (EMA), vimentin, CD56, and progesterone. Cytokeratin, thyroid transcription factor-1, and CD34 were negative. Finally, the diagnosis of MPMNs was established, and there was no evidence of malignancy. On the second postoperative day, the patient was discharged without any complications. Currently, he is being followed-up with at our hospital and is doing well.