[Melanotic neuroectodermal tumor in a newborn]. / Melanoticheskaia neiroéktodermal'naia opukhol' u novorozhdennogo.

The tumor consists of two types of cells: small with abundant processes cells capable of dividing and probably being neuroblasts, and the big melanocytes forming bands and glandular-like structures. Tumor cells (mainly melanocytes) express pancytokeratins, S-100 protein, neuron-specific enolase, synaptophysin and melanin antigen. These data are the additional indication that melanotic neuroectodermal tumor is the derivative of the neural crest.

Melanotic neuroectodermal tumour of infancy: an immunohistochemical and ultrastructural study.

Two cases of melanotic neuro-ectodermal tumour of infancy (MNTI)--a rare neoplasm arising in the first year of life--are reported, with the results of immunohistochemical and ultrastructural examination. The tumours consisted of a biphasic cell population in a fibrous stroma. The small, darkly staining cells comprising the first population stained positively for synaptophysin, showing them to be neuroblasts, and the large epithelioid cells comprising the second cell population stained positively 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 neurofilaments in the neuroblastic population, and melanosomes in the epithelioid population. These results add to the evidence supporting the neural crest origin of MNTI and confirm its formation from two distinct cell lines. Both cases have responded to local excision, with no recurrence more than a year after initial treatment.

Usefulness of electron microscopy in the diagnosis of "small" round cell tumors of the sinonasal region.

The sinonasal region is known to harbor several types of tumors that belong to the general category of "small" round cell tumors and offer considerable diagnostic challenges. This study evaluated 33 cases of such tumors by electron microscopy to characterize their ultrastructural features in conjunction with immunohistochemistry, in an attempt to define diagnostic criteria of various types. Electron microscopy was useful in the proper classification of tumors in 27 cases: esthesioneuroblastoma (EN), 12; undifferentiated carcinoma, 6; melanoma, 3; lymphoma, 3; melanotic neuroectodermal tumor, 1; rhabdomyosarcoma, 1; and pituitary adenoma, 1. In the remaining six cases, the ultrastructural features were those of poorly differentiated carcinomas. They usually exhibited some epithelial characteristics as well as neuroendocrine features by immunohistochemistry and electron microscopy. These tumors could be best described as poorly differentiated neuro-endocrine carcinomas (malignant neuroepitheliomas). The most controversial diagnostic problems existed between the tumors categorized as esthesioneuroblastomas and neuroendocrine (NE) carcinomas. Esthesioneuroblastomas were characterized by uniform round nucleated cells with variable amounts of dendritic processes containing numerous dense core granules ranging from 150 to 350 nm in the perikarya and dendritic processes. Dendritic processes contained longitudinally arranged neural tubules and revealed an occasional synaptic junction. In three of the 12 cases of EN, cells with the appearance of sustentacular cells were recognized by electron microscopy. The NE carcinomas usually consisted of closely packed round cells with scanty cytoplasm that lacked any feature of neuroblastic cells. The tumor cells in this category often were epithelioid in appearance and exhibited a varying degree of cytokeratin positivity. Neuron-specific enolase was also positive in all cases, further suggesting their neuroepithelial nature. The greatest difference between EN and NE carcinomas was the absence of sustentacular cells in NE carcinomas. Immunohistochemical and electron microscopic studies are essential in the differential diagnosis of EN and NE carcinomas, because their microscopic appearance is very similar. The study indicates that EM is useful in the diagnostic categorization of sinonasal tumors of uncertain nature, particularly when it is used in conjunction with immunohistochemistry.

Malignant melanotic neuroectodermal tumor of infancy.

A 2-month-old boy underwent surgery for removal of a right temporal melanotic neuroectodermal tumor of infancy (MNTI). Histologically the tumor tissue showed signs of malignancy. The child was reexamined several times up to the age of 5 years. Neuroradiological evaluation showed no evidence of tumor recurrence or metastases. No resulting handicap was observed during neurological and psychological follow-up examination at the age of 5 years. Our findings confirm that surgical removal as the therapy of choice provides an excellent prognosis for this kind of tumor in spite of its histologically malignant appearance.