MELANOTIC NEUROECTODERMAL TUMOR OF INFANCY - AN IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL-STUDY

Two cases of melanotic neuro-ectodermal tumour of infancy (MNTI)-a rar e neoplasm arising in the first year of life-are reported, with the re sults of immunohistochemical and ultrastructural examination, The tumo urs consisted of a biphasic cell population in a fibrous stroma, The s mall, darkly staining cells comprising the first population stained po sitively for synaptophysin, showing them to be neuroblasts, and the la rge epithelioid cells comprising the second cell population stained po sitively with the antibodies HMB-45 and NKI-Beteb, showing them to be melanocytes. Ultrastructural examination of the second case confirmed the biphasic nature of the tumour cells, with secretory granules and n eurofilaments in the neuroblastic population, and melanosomes in the e pithelioid population, These results add to the evidence supporting th e neural crest origin of MNTI and confirm its formation from two disti nct cell lines, Both cases have responded to local excision, with no r ecurrence more than a year after initial treatment.