A 67-yr-old man visited with a lung mass that had been detected incidentally on chest roentgenogram taken during the national insurance screening program. The chest PA and left lateral films revealed an approximately 4-cm sized well-defined mass at the left lower lobe (). Computed tomography showed a mass with a smooth margin and the tumor had well enhanced linear opacity inside of the contrast enhancement. The mass was not connected to the pleurae, chest walls, or other adjacent organs ().
(A, B) An approximately 4 cm round solitary mass is shown at the left lower lung field on posterior-anterior and left lateral chest roentgenograms. (C) The chest CT scan showing a heterogeneously contrast-enhancing mass lesion in the left lung.
The origin of the mass and metastasis was verified by examining the whole body bone scan, PET/CT scan with 2-[18F] fluoro-2-deoxy-D-glucose (FDG), and brain magnetic resonance imaging (MRI). On bone scan, there were no active skeletal lesions. Neither the kidney nor soft tissue showed any abnormal uptake. The FDG-PET scan revealed intense and homogenous hypermetabolic activity with a metabolic defect at the left lower lobe of the lung. The 1-hr maximum standardized uptake value (SUV) was 6.22. Except for the lung lesion, there was no abnormal hypermetabolic lesions or metabolic defects. Therefore we confirmed the lung was the primary focus of the mass, and there were no distant metastases.
A percutaneous needle biopsy was performed with 19 G thru cut needle under fluoroscopic guidance. Hematoxylin and eosin (H-E) staining showed a solidly packed round cell pattern with a striking uniformity. The individual cells had a small round to ovoid nucleus with a distinctly unclear membrane, fine powdery chromatin, and one or two minute nucleoli. The cytoplasm was ill-defined, scanty, and pale stained (). Some of the cells had irregularly vacuolated cytoplasm secondary to glycogen deposition, which was positive for Periodic Acid Schiff (PAS) stain (). The tumor cells showed a strong membranous MIC-2 immunoreactivity ().
Fig. 2 (A) Light microscopy of the tumor shows uniformly solidly packed round cells with a distinct unclear membrane (H&E, ×400). (B) Irregularly vacuolated cytoplasm secondary to glycogen deposition (PAS, ×400). (C) Strong membranous (more ...)
The other markers including cytokeratin (CK), small cell lung cancer (SCLC), chromogranin, CK7, CK19, and thyroid transcription factor 1 (TTF-1) were all negative. Vimentin, synaptophysin, and p63 stained focally, and more than 90% of the cells were positive for Ki-67 labeling. All the pathological findings were compatible with a ES/PNET of primary pulmonary origin.
After pathological diagnosis, surgical resection of the left lower lobe of the lung was done. Serial sections of the lung showed that the cut surface had a well demarcated round whitish soft mass, which had extensive tumoral necrosis. The mass was not connected to the bronchi or vessels. It was 5 cm apart from the nearest bronchial resection margin and 0.5 cm from the nearest visceral pleura (). Using the tissue obtained after surgical resection, fluorescence in situ hybridization (FISH) was performed using the LSI® Ewing sarcoma breakpoint region 1 (EWSR1) 22q12 Dual Color Break Apart Rearrangement Probe and revealed EWSR1 22q12 rearrangement in 82% (164 out of 200 cells) ().
Well demarcated whitish soft tissue mass having extensive tumoral necrosis inside.
Fluorescence in situ hybridization revealed EWSR1 22q12 rearrangement detected by using LSI® EWSR1 (22q12) Dual Color Break-Apart Rearrangement probe.
Ultimately, the diagnosis was established to be a 4-cm sized ES/PNET arising primarily from the lung with no regional invasion to the bronchi, visceral, or parietal pleurae. In addition, there was no perihilar lymph node invasion (all 4 of 4) or distant metastasis. After surgery, the patient was administered with combination chemotherapy with vincristin, actinomycin, and cyclophosphamide.