Primary peripheral neuroectodermal tumor (PNET) of the adrenal gland: a rare entity

Purpose: Ewing Sarcoma/Primitive Neuroectodermal Tumor (ES/PNET) is a malignant small round cell tumor belonging to the Ewing Sarcoma Family of Tumors. It occurs more commonly in children and young adults. Its localization in the adrenal gland is extremely rare. We reviewed 35 cases of ES/PNET of the adrenal gland reported in the literature and presented our case. Methods: Data were collected by searching for ES/PNET and adrenal gland key words on Google Scholar and PubMed in March 2018, including a case diagnosed in our department. We analyzed all reviewed cases for diagnosis, surgical and systemic therapy and outcome. Results: To date 24 articles presenting cases of ES/PNET of the adrenal gland are reported in the literature. We included in our review 35 cases previously described and one new case. Histologically all cases consisted of sheets of small round cells. Immunohistochemistry was also performed in all cases. Most cases stained positive for CD99 and negative for lymphocytic markers. Markers of epithelial differentiation displayed variable results. In all cases tested, characteristic translocations were displayed supporting the diagnosis. All patients but four were treated surgically and the majority received adjuvant therapy. Only very few cases received neoadjuvant chemotherapy. Conclusions: Primary ES/PNET of the adrenal gland is a rare tumor, showing specific morphological, immunohistochemical and cytogenetic characteristics. Treatment consists of surgery, chemotherapy and radiotherapy. Further investigations paired with long term follow-up are necessary to define prognosis for this rare entity.