Molecular genetics changes in melanocystic lesions – case report

Introduction: The worldwide incidence of malignant melanoma is increasing annually more than 4%. Some forms of nevocellular lesions are a diagnostic problem in morphological terms; particularly in cases of pigmented lesions of benign nature, such as Spitz naevus. A correct determination of biological nature of the neuroectodermal tumour is one of the basic prerequisites for a proper treatment. Histological examination is the gold standard to establish the diagnosis. Although many cases may be reliably classified according to current histopathological criteria, there is a group of cases in which an agreement has not been reached even among experts. Molecular genetic studies show that the difference between melanomas and benign nevocellular lesions consists of a multiplication or loss of specific chromosomal regions. In melanomas, using the CGH method, the most frequent deletions were found in regions 6q, 8p, 9p and 10q, and the most frequent amplifications in regions 1q, 6p, 8q, 17q, 20q and over the entire chromosome 7. Based on these studies a combined probe Vysis LSI RREB1/LSI MYB/LSI CCND1/CEP 6 (Abbott, USA) was developed, which can be used to detect numeric alterations associated with malignant melanoma as a diagnostic aid for formalin fixed, paraffin embedded sections.

Aim: Case report

Material and methods: Nevoid skin lesion of the left arm of seventy years old woman, 10 mm in diameter, was removed in 2006. Material was sent for histological examination with a diagnosis of benign naevus. Conclusion of the histological examination was dysplastic familiar naevus. In april 2010, reexcision of the scar recurrence was performed. Clinical diagnosis defined as malignant melanoma. Conclusion of histological examination was supperficial spreading melanoma.

For the identification of genetic changes associated with diagnosis of malignant melanoma in the sample from the year 2010 Multi Colour FISH (Fluorescence In Situ Hybridisation), the combined probe Vysis LSI RREB1/LSI MYB/LSI CCND1/CEP 6 (Abbott, USA) has been applied. The same assay was used in the sample from the year 2006.

Results and conclusions: Using Interphase FISH method in the sample from the year 2010 (histology: supperficial spread melanoma) pathological finding was proven - amplification of gene CCND1 (lokus 11q13) in all examined tumour cells. We examined 30 nonoverlapping cells from 3 different areas of the tumour. In the material from the year 2006 we found isolated cells with the same aberration as in the first examined sample from the year 2010 – the amplification of gene CCND1.

While, using the current histopathological criteria, the sample was diagnosed in 2006 as a rather dysplastic familiar naevus, genetic changes associated with the diagnosis of malignant melanoma in isolated cells were also found. Molecular testing seems to be a useful tool for diagnosing skin lesions.