Atypical presentation of primary cutaneous CD8 positive aggressive epidermotropic cytotoxic t-cell lymphoma

Primary cutaneous CD8 positive aggressive epidermotropic cytotoxic T-cell lymphoma (PCAT) is a rare and heterogeneous entity with less than 100 published cases to date. A 68-year-old man was following up for an inflammatory lichen–lupus overlap dermatosis of 3 years duration. Treatment with methotrexate was started, observing a dramatic change in the skin lesions that became infiltrated plaques and generalized ulcerated tumours distributed over trunk and extremities. Histological study showed marked epidermotropism of CD8 positive cells and monoclonality was demonstrated by the polymerase chain reaction. Diagnosis of PCAT was concluded. Treatment with polychemotherapy was indicated. The PCAT is characterized by a rapid clinical history of generalized papules, plaques, nodules and tumours with frequent ulceration and necrosis. Although it has no pathognomonic clinical features, there are clinical, histological and prognostic data that define them as a group and differentiate them from other lymphomas. Exceptionally, there are cases reported which have been triggered following treatment with immunosuppressive drugs. In our patient we think that PCAT was triggered by the transformation of a pre-existing dermatosis, which had never showed a lymphoproliferative profile in biopsies before. A possible pathogenic mechanism is that in some inflammatory dermatoses, chronic antigenic stimulation in a situation of iatrogenic immunosuppression may favour the development of a malignant clonal T cell.