Left inguinal lymphadenopathy as the solitary metastatic presentation of primitive neuroectodermal tumor of unknown origin

Primitive neuroectodermal tumor (PNET)/ewing′s sarcoma is a rare neural crest tumor of central nervous system, thoracopulmonary regions, pelvis, and lower extremities. Visceral involvement by PNET is a rare phenomenon, with kidney being the most commonly involved organ. We report a 35-year-old Asian female presenting with left inguinal swelling, with computed tomography scan evidence of conglomerate lymph nodal mass in the left external iliac and inguinal region. A clinico-radiological diagnosis of lymphoproliferative disorder was made. She subsequently underwent excision biopsy. Histopathology of the biopsy specimen revealed completely effaced lymph nodal architecture, which was replaced by a tumor composed of nests of small, round, blue cells. On immunohistochemistry, the tumor cells were positive for CD99 and negative for CD3, CD20, leucocyte common antigen, epithelial membrane antigen, cytokeratin, desmin, vimentin, synaptophysin, and chromogranin A. Extensive search regarding any possible different site of involvement by the tumor was negative. The clinical presentation and histological, cytological, and immunohistochemical pattern, lead to the diagnosis of metastatic PNET of the left external iliac and inguinal lymph node with unknown primary origin. To the best of our knowledge, it is the first ever reported case of inguinal lymphadenopathy as the solitary metastatic presentation of PNET of unknown origin.