Long-term survival after solid-organ transplantation is increasing because of recent advances, including new immunosuppressive regimens to avoid graft rejection. However, the resultant modification of the immune system is associated with an increased risk of several cancers. The most common are skin cancers, and lymphomas are second in frequency. Nevertheless, posttransplant primary cutaneous lymphomas (PCLs) are rare, and their incidence is not well known currently. From the files of the Nephrology and Cardiology Departments of University Hospital "12 de Octubre" of Madrid, we obtained clinical data from 1612 transplanted patients and only found 2 cases of posttransplant PCLs, both were T-cell PCL. We reviewed the clinical, histopathological, and immunohistochemical characteristics; both cases were T-cell posttransplant PCLs manifested clinically as mycosis fungoides. One was a 57-year-old woman who had received a cadaveric kidney transplant, and the other was a 60-year-old man with a heart transplant. Histology and immunohistochemistry were consistent with the features of mycosis fungoides when lesions were completely developed. Up to 20% of all organ transplant recipients will suffer some form of malignancy. Unlike general population, 70% of PCLs in transplant recipients are B cell in origin and frequently show positivity for Epstein-Barr virus markers; whereas only 30% are cutaneous T-cell lymphomas. Different pathogenic hypothesis including reduced immune surveillance, chronic antigenic stimulation by transplant grafts, and the direct oncogenic effects of immunosuppressive drugs have been suggested. Although cutaneous B-cell lymphomas are more common, dermatopathologists should be aware that cutaneous T-cell lymphomas may also appear.