Unohistochemical positivity for CD99, NSE, synaptophysine, and Rosiglitazone chromogranine A are very useful in differential diagnosis. Furthermore, the presence of Homer-Wright rosettes are typical for neuroblastomas, which are also positive for NSE, synaptophysine, and chromogranine A, but negative for CD99. LCA positivity supports the diagnosis of lymphoma, but T cell lymphoblastic lymphoma may be negative for LCA and positive for CD99 and CD3. Small-cell carcinoma is almost always positive for cytokeratin, while rhabdomyosarcoma is positive for desmin, actin, myoglobulin, and monophasicShi et al. Diagnostic Pathology 2013, 8:51 http://www.diagnosticpathology.org/content/8/1/Page 4 ofsynovial sarcoma is positive for CD99, cytokeratin , EMA. The desmoplastic small round cell tumor is characterized by sharply circumscribed nests or clusters of small, undifferentiated cells surrounded by a desmoplastic stroma, and show positivity for cytokeratin and desmin, but negativity for CD99. Therefore, the phenotypes observed in our case, i.e., positive expression of CD99, vimentin, NSE, and synaptophysin, and negative expression of cytokeratins, CD3, desmin, and LCA, are highly suggestive of a pulmonary PNET [3,9-11]. Despite the patient's history of pulmonary PNET and imaging findings that were consistent with primary pancreatic cancer, we initially suspected primary serous cystic pancreatic neoplasm because metastasis of a PNET to the pancreas had never been previously reported. However, the patient's histological findings indicated no transition had occurred from the pancreas to the neoplastic tissue. In addition, there were no clinical signs of chronic pancreatitis in the surrounding parenchyma. Considering the expression of CD99, NSE, and synaptophysine, as well as the primary pulmonary PNET, we believed the findings strongly supported a diagnosis of metastatic pancreatic PNET. According to the literature, there have only been nine reported cases of PNET originating from the lung without pleural or chest wall involvement [9,12-17]. Ages of the reported patients have ranged between 8 to 67 years, with a mean age of 33 years. There is a slight male predominance, with the male:female ratio being 5:4. Five of the cases originated from the left lung and four from the right. Despite treatment with various combinations of surgery, chemotherapy, and radiation therapy, the survival rate in the previous reports was poor; typically, the two-year survival rate after operation is 33.3 . Of the nine reported cases, seven were followed-up; four were alive without disease at eight months, 16 months, 22 months and two years after surgery, and three had died at three months, two years, and two years after operation due to local recurrence or widespread metastatic disease. Furthermore, the predominating metastatic sites are the lungs, adrenal glands, and ovaries. In our case, no adjunct radiation or chemotherapy was given after the initial surgery, due to patient refusal. However, recurrence was detected at sixteen months after the first resection and appeared as a metastasis to the pancreas. The patient underwent the second radical surgical resection of the metastatic tumor. Adjunct radiation or PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/17139194 chemotherapy again refused by the patient after the second surgery. To date, no evidence of tumor recurrence or metastasis has emerged. The patient has survived 32 months after the second surgery. The long-term survival of the patient may have been a result of the two radical surg.