Lymphoblastic lymphoma (LBL) is a neoplasm of precursor B- or T-lymphocytes, and primary skin involvement is uncommon. The aim of the study was to review all reported primary cutaneous (PC)-LBLs and to examine three new cases to better characterize this neoplasm. Two of our patients showed a pre-B phenotype (PC-B-LBL) and one a never-reported pre-T phenotype (PC-T-LBL). The patient with PC-T-LBL showed an aggressive course, while those with PC-B-LBL showed a complete remission (CR) after polychemotherapy. Cytogenetic analysis and gene expression profiling (GEP) were performed on one case of PC-B-LBL and on that of PC-T-LBL. A specimen of PC-B-LBL and two specimens (early and late stage) of PC-T-LBL were investigated by microarray-based comparative genomic hybridization (CGH). All specimens revealed trisomy of chromosome 4. PC-T-LBL showed a gain of 1p36.33-p22.1 in the early stage and multiple chromosome gains/losses in the late stage. Our data suggest that trisomy 4 could be detected early in LBL and gain of 1p36.33-p22.1 could be an interesting marker in PC-T-LBL. LBL is an aggressive disease but, only in B-LBL, the cutaneous presentation seems to be a favorable prognostic factor and polychemotherapy is the best therapeutic approach. We suggest that PC-LBL should be included as a provisional clinicopathologic entity in future cutaneous lymphoma classification.