DISCUSSION: PNET are rare tumors occurring in the posterior sulcus or chest wall. Usually painful, these invasive thoracic tumors may develop on and invade chest wall, lung, or mediastinum1. The pathological differentials of lung PNET include small cell carcinoma and other small round-cell tumors, such as malignant lymphoma, Langerhans’cell histiocytosis, rhabdomyosarcoma, and synovial sarcoma with the characteristic pathology of nests of small cells and Homer-Wright pseudo-rosettes with an acidophilic positivity of neurofibrillar elements2. Our patient's biopsy showed infiltration with round and spindle shaped tumor cells. However, CK, Thyroid transcription factor (TTF1), P63, CALRETININ, HBME1 markers were negative on IHC. Further, Vimentin and CD-99, S100 and NSE were positive, with Ki-67 positivity of 70%; clinching the diagnosis of malignant neuro endocrine tumor3. As PET was negative for distant metastasis, the diagnosis of primary pleural PNET was considered.