Perivascular epithelioid cell tumors (PEComas) are unusual mesenchymal neoplasms composed of histologically and immunohistochemically distinct perivascular epithelioid cells (PECs). Although PEComas have the potential to behave in a malignant fashion, malignant PEComas arising from the retroperitoneum are extremely rare. A 68-year-old woman presented with a painful palpable mass in her left upper abdomen. Computed tomography of the abdomen showed a 9 cm sized heterogeneous mass in left para-aortic space and multiple hypervascular nodules in the liver. 18F-fludeoxyglucose-PET/CT showed multifocal hypermetabolic lesions in retroperitoneum, liver, and skeletal bones. Percutaneous needle biopsies were done on the retroperitoneal and hepatic mass. Both specimens were positive for human melanoma black-45 (HMB-45) on histological and immunohistochemical staining which was compatible with PEComas. Herein, we report a rare case of retroperitoneal PEComa with multiple metastases involving liver and bone at initial diagnosis that exhibited aggressive behavior and resulted in a devastating prognosis.
Aged ; Bone Neoplasms/pathology/radiography/secondary ; Female ; Fluorodeoxyglucose F18 ; Humans ; Liver Neoplasms/pathology/radiography/secondary ; Perivascular Epithelioid Cell Neoplasms/*diagnosis/pathology ; Positron-Emission Tomography ; Tomography, X-Ray Computed

Clear cell tumor of the lung is a rare and very unusual benign pulmonary tumor. As clear cell tumor of the lung contains abundant cytoplasmic glycogen, this tumor is called "sugar tumor". We report a case of sugar tumor in a 64-yr-old man presenting as a round pulmonary nodule. On dynamic computed tomography (CT) scans, the solitary pulmonary nodule showed early wash-in enhancement with an early washout pattern like a lung malignancy. The patient underwent wedge resection for the tumor. Pathologic examination, including immunohistochemical studies, revealed that the nodule was a benign clear cell tumor, so-called "sugar tumor". Because only a small number of cases have been reported previously, clinical aspects, radiological characteristics on dynamic contrast-enhanced CT, and differential diagnosis of the tumor are not well established. Herein we present a clear cell tumor of the lung and discuss the clinical, radiological, and pathological features of the tumor.
Antigens, Neoplasm/metabolism ; Diagnosis, Differential ; Humans ; Lung/radiography/surgery ; Lung Neoplasms/diagnosis/pathology/*radiography ; Male ; Middle Aged ; Neoplasm Proteins/metabolism ; Perivascular Epithelioid Cell Neoplasms/diagnosis/pathology/*radiography ; Solitary Pulmonary Nodule/diagnosis/pathology/*radiography ; *Tomography, X-Ray Computed