Certain difficulties arise in the differential diagnosis between Reed nevus that is common in children and adolescents and cutaneous melanoma that is extremely rare in patients of this age group. In addition to the classical histological examination, an immunohistochemical test for marker proteins is carried out to improve the accuracy of the diagnosis of pigmented skin neoplasms.

OBJECTIVE

To evaluate the suitability of a set of proteins (cyclin D1, p16^INK4a, and HLA class I antigens) in the differential diagnosis of Reed nevus and cutaneous melanoma in children and adolescents.

MATERIAL AND METHODS

Three samples of pigmented skin neoplasms were taken during surgical treatment in patients at the Blokhin National Medical Research Center of Oncology: two samples of Reed nevus (from a 9-year-old girl and a 15-year-old boy) and a sample of cutaneous melanoma that had developed in an 8-year-old boy. The materials were presented by paraffin blocks. Immunohistochemical staining was performed using antibodies against cyclin D1, p16^INK4a, and HLA class I antigens.

RESULTS

Differences were found between nevus and melanoma in the expression of all three markers. Thus, the nuclear expression of cyclin D1, a proliferation activator, occurred in some cells in the nevus samples and in the vast majority of cells in the melanoma samples. The nuclear expression of the cell cycle inhibitor p16^INK4a was dramatically reduced in melanoma compared to nevus. HLA class I antigens were detected on the surface of individual nevus cells, but were completely absent on the membranes and in the cytoplasm of melanoma cells, which could promote the evasion of this tumor from the body’s immunological supervision.

CONCLUSION

Immunohistochemical test for the proteins cyclin D1, p16^INK4a, and HLA class 1 antigens is a promising approach to differentially diagnosing between Reed nevus and cutaneous melanoma in children and adolescents.