Background: The cytologic features of melanotic neuroectodermal tumor of infancy (MNTI) have been described in rare cases only, and these reports have been based solely on direct smears obtained from aspirated tumor material or from touch preparations of resected tumors.
Case: We report, to our knowledge, the first documented case of an epididymal MNTI diagnosed from aspirated hydrocele fluid processed using the ThinPrep system (Cytyc Corp., Boxborough, Massachusetts, U.S.A.).
Conclusion: Based on a 15 year retrospective review of scrotal fluids submitted for cytologic evaluation to our laboratory, MNTI represented the sole neoplasm that was represented in the fluid and could be specifically diagnosed. Compared to the direct smear evaluation in our case and other published reports, the ThinPrep method enables the recognition of both neuroblast-like cells and larger melanin-containing epithelial cells in scrotal fluid, thereby aiding in the specific diagnosis of MNTI and minimizing the risk of misdiagnosing this tumor as a more aggressive neoplasm.