Morphology of neuroblastoma

One of the distinctive features of neuroblastoma is the ability for spontaneous regression, reminiscent of the reverse development of the sympathetic nervous system during embryogenesis. Sympathetic chromaffinic paraganglia appear in the early stages of embryonic development in the adrenal medulla. By the eighth week of embryogenesis, the hormonal-active parenchymal cells of the adrenal system reach large sizes, and at the time of birth sharply decrease.

Another characteristic feature of neuroblastoma is the ability to differentiate in vitro under the influence of various factors (retinoic acid, nerve growth factor, papaverine). At the same time, in vivo, the tumor is characterized by extremely aggressive growth and rapid metastasis.

Screening studies of neuroblastoma revealed a multiple increase in the frequency of this tumor in infants of the first half of life. This discrepancy with the reported morbidity is explained by the phenomenon of spontaneous reverse development of neuroblastoma in most cases. Regression, as a rule, occurs with certain biological characteristics of the tumor: the triploid set of chromosomes, the lack of amplification of the MYC gene and the anomaly of the first chromosome (loss of the short arm). With the possibility of spontaneous tumor regression, the absence of expression of telomerase and the neurotrophin TRK-A receptor is also associated.

Morphology of neuroblastoma

Histological diagnosis of neuroblastoma may present significant difficulties due to the morphological similarity of this tumor with primitive neuroectodermal tumors, lymphomas and rhabdomyosarcoma.

Tumor cells in neuroblastoma are similar to embryonic neuroblasts of sympathetic tissue. Microscopically, the tumor is represented by small circular neuroblast cells with large nuclei and a narrow rim of the cytoplasm. In the tumor tissue, three main components can be distinguished: neuroblastomatous, ganglionioromatous and intermediate. The predominance of this or that component determines the degree of differentiation of the neuroblastoma. Allocate undifferentiated (all tumor cells are represented by neuroblasts), low-grade (ganglion cell differentiation is noted in less than 5% of cells) and differentiated (more than 5% of cells have signs of differentiation) type of neuroblastoma. The prognosis is most favorable in the latter type of tumor.

Integral classification (1986) is convenient for determining the prognosis in clinical practice. This classification relates indicators such as the age of the patient and the histological features of neuroblastoma (the degree of differentiation of neuroblasts, the severity of the stromal component, the mitosis / karyorexis index). According to this classification, the prognosis is most favorable when a well-differentiated type of tumor is combined and the child's age is less than 1 year.

Molecular-genetic aspects of neuroblastoma

Currently, there are some genetic anomalies that are characteristic of neuroblastomas and determine the prognosis of the disease. The most significant genetic anomaly is the amplification of the N gene of the ICC. Regardless of the age of the patient, the detection of this anomaly has unfavorable prognostic significance. Amplification of N MUS often combines with deletion of the short arm of the first chromosome and an increase in the long arm of chromosome 17. The last aberration itself has an unfavorable prognostic value.

The hyperploid set of chromosomes in tumor cells is associated with a favorable prognosis, especially in children of the first year of life. Increased expression of the neurotrophin-TRK-A receptor gene is another favorable prognostic sign of neuroblastoma.

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