Cell-free Circulating DNA in Primary Cutaneous Lymphomas

Primary cutaneous lymphomas represent the second extra nodal localization of lymphomas, and are constituted by T-cell and B-cell phenotype lymphomas. Mycosis fungoides, a T-cell epidermotropic lymphoma, is the most frequent. Its clinical behavior is usually indolent but some patients have an aggressive evolution. Among B-cell cutaneous lymphomas, primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT) is the most aggressive. Cytogenetic and molecular studies on these tumours led to a genetic characterization of these entities. Therefore, there is not any biologic marker that can help monitoring these lymphomas. In solid tumors, mutations exhibited by the tumour tissue has been detected in plasma of patients, assessing the possibility to detect cell-free circulating tumoral DNA in a blood sample, with correlations with clinical characteristics and metastatic outcome. The concept of liquid biopsies, allowing the detection of tumour mutation in plasma has been validated in nodal diffuse large B-cell lymphoma. That's why the purpose is to evaluate the possibility to detect cell-free circulating tumoral DNA in primary cutaneous lymphomas, using a highly sensitive method (digital PCR), combined with a next generation sequencing panel of the tumour sample.

Inclusion criteria

• age > 18 years;
• French social security system affiliation or equivalent;
• Patient with an aggressive cutaneous lymphoma (PCDLBCL-LT, mycosis fungoides, T helper follicular cutaneous lymphoma) diagnosed and monitored at the university hospital of Bordeaux;
• Written and informed consent obtained for genetic blood test;
• Biopsy sample available for molecular analysis.

Exclusion criteria

• Another cancer (except "in situ" and surgery treated cutaneous carcinomas) in the precedent 5 years.