Primary cutaneous T-cell lymphomas (CTCL) are a form of skin cancer that is derived from immune cells. The most common form of CTCL is mycosis fungoides (MF). While initially confined to the skin, MF may spread to lymph nodes, blood or inner organs, resulting in an overall poor prognosis for the patient. Thus, being a potentially lethal disease, an early and correct diagnosis of MF has very important implications for the patient. However, diagnosis of early MF is often difficult, as it usually shows a close resemblance to benign inflammatory conditions such as eczema and psoriasis. Strikingly, it takes an average of 3-6 (!) years from the appearance of the first skin lesions until a diagnosis of MF can be made. For this reason, a test to distinguishing early MF from benign inflammatory conditions is urgently mandated. By using skin suction blister fluid as well as skin biopsies from patients with MF, eczema and psoriasis, the investigators want to develop a classifier system that can distinguish early MF from benign inflammatory skin diseases.

Inclusion Criteria:

• Clinical and/or histopathological diagnosis of MF, eczema or psoriasis
• Healthy control subjects without personal history of MF, eczema or psoriasis

Exclusion Criteria:

• Ongoing skin-targeted treatment (Wash out times: 2 weeks for topical, and 4 weeks for systemic treatments)
• Ongoing other treatment that might, in the opinion of the investigator, influence proteomic features of the samples to be acquired

MF patients need prior histopathological verification of their disease.

Eczema and psoriasis patients will be diagnosed clinically and, if necessary, on a histopathological basis.