ABSTRACT
Neuroendocrine neoplasms represent a heterogeneous group of rare tumors, more frequently arising from gastroenteropancreatic tract and lungs. At the time of diagnosis, 20% of cases are metastatic, and 10% of cases are considered as cancer of unknown primary origin. Several immunohistochemical markers are routinely used to confirm the neuroendocrine differentiation, first among all Synaptophysin and Chromogranin-A; on the other hand, different immunohistochemical markers are used to establish primary anatomical site, as TTF1, CDX2, Islet-1 and Calcitonin, but no marker is available in order to distinguish among different sites of the digestive tract. DOG1 (discovered on GIST-1) is a gene normally expressed in interstitial cells of Cajal and, in routine practice, DOG1 immunostaining is used in diagnosis of GIST (gastrointestinal stromal tumor). DOG1 expression has been described in several neoplasms other than GIST, both in mesenchymal and epithelial neoplasms. In the present study, DOG1 immunostaining has been performed in a large cohort of neuroendocrine neoplasms, including neuroendocrine tumors and neuroendocrine carcinomas, in order to evaluate frequency, intensity and pattern of expression in different anatomical site and in different tumor grade. DOG1 expression was detected in a large percentage of neuroendocrine tumors, with statistically significant association between DOG1 expression and gastrointestinal tract neuroendocrine tumors. As a consequence, DOG1 could be included in marker panel for the identification of primary site in neuroendocrine metastases of unknown primary origin; moreover, these results recommend careful evaluation of DOG1 expression in gastrointestinal neoplasms, in particular in differential diagnosis between epithelioid GIST and neuroendocrine tumors.
ABSTRACT
Merkel cell carcinoma (MCC) is a skin cancer of neuroendocrine origin that occurs most often in sun-exposed areas. In the general population, it is a disease of older adults, with only 5% of cases occurring below the age of 50 years. Immunosuppression is the significant risk factor for the development of MCC and recently it was suggested that individuals with HIV have a relative risk of 13.4 to developed MCC in comparison with the general population. We report a case of MCC in an HIV-infected patient and we review nine patients with HIV with MCC. Our patient was a 54-year-old man who came to our attention without a known HIV diagnosis. He was apparently in good health and had no risk factor for HIV, but by the atypical site of the lesion and by the relative young age of the patient we suspected a case of immunosuppression and for this reason we did HIV test that had a positive result. The patient was treated with surgery and chemotherapy but died as a result of liver metastases 25 months after his tumor was diagnosed.
