Cytogenetic/mutation profile of chronic lymphocytic leukemia/malignant melanoma collision tumors of the skin.

Background: Collision tumors are rare entities that consist of two histologically distinct tumor types arising in the same anatomic site. An association between chronic lymphocytic leukemia (CLL) and malignant melanoma (MM) has been already described. Up to now, they have been documented only at positive regional lymph nodes while we focused on collision tumor in a skin lesion.

Case Presentation: We characterized the genomic profile of a skin CLL/MM collision tumor in a patient with a 9-years story of CLL. Typical high-grade genomic biomarkers featured the CLL: the immunoglobulin heavy variable genes were unmutated; a clonal del(11q), involving and , was present in the peripheral blood (PB) and skin lesion, while a subclonal large del(13q)/D13S319 was detected only in the PB. Interestingly, the del(13q) clone, increased from 10% to 46% from diagnosis to relapse. , , and were wild type. The MM lesion carried a and a promoter mutation.As the family story was consistent with a genetic predisposition to cancer, we performed mutational analysis of genes involved in familial melanoma and CLL, and of and . No germinal mutation known to predispose to CLL, MM, or breast cancer was found. Interestingly, conventional cytogenetic detected a constitutional t(12;17)(p13;p13).

Conclusions: Our data are consistent with distinct genetic landscape of the two tumors which were characterized by specific disease-related abnormalities. CLL cells carried poor prognostic imbalances, i.e. large deletions of the long arm of chromosomes 11 and 13, while in MM cells two functionally linked mutations, i.e. and a promoter occurred. Although, known germline variations predisposing to MM and/or CLL were ruled out, genetic counseling suggested the proband family was at high risk for MM.