Non random cytogenetic changes characterize Merkel cell carcinoma

Merkel cell carcinoma is a rapidly proliferating neoplasm of neuroectodermal origin presenting in skin. Karyotypes obtained in direct preparations of three Merkel cell carcinomas were analyzed and compared with six other tumors which were reported in the literature. Of the nine tumors studied so far, eight (89 per cent) showed structural abnormalities of chromosome 1. These abnormalities were in the form of trisomy for chromosome 1q22----ter. Furthermore, it was also observed that the breaks of these rearrangements on chromosome 1 occurred at the bands to which c-oncogenes N-ras (p31), L-myc (p32), c-src (p36), c-ski (q22-22), and the beta-subunit of the nerve growth factor (NGF) (p22) were localized. In addition to structural changes, five out of the nine tumors (55.5 per cent) were trisomic for chromosome 1. Merkel cell tumors are often confused with small cell carcinoma of lung or peripheral neuroepithelioma. The cytogenetic abnormalities such as rearrangement of chromosome 3p and t(11;22)(q23;q12) which characterize lung carcinoma and peripheral neuroepithelioma, respectively, were not seen in any of the nine Merkel cell tumors studied. Thus it appears that rearrangement of chromosome 1 was non-randomly associated with Merkel cell carcinoma. It is of interest to note that genes involved in neuronal development and or differentiation have been mapped to the bands at which breaks occurred in these tumors. The significance of these changes is briefly discussed.