Large plaque parapsoriasis (poikiloderma vasculare atrophicans) can progress to mycosis fungoides. Treatment of large plaque parapsoriasis includes UVB or PUVA therapy. Patients with large plaque parapsoriasis should be followed at regular intervals (at least every six months). Sequential biopsies of the thickest lesions may be necessary to confirm progression to a true Cutaneous T cell lymphoma such as mycosis fungoides or Sézary syndrome.

Follicular mucinosis or lesions similar to lymphomatoid papulosis may be associated with mycosis fungoides in 10-15% of cases. Assessment at the Vancouver Cancer Centre may be useful. True lymphomatoid papulosis is a separate disease and does not evolve into T-cell lymphoma (see section on Lymphoma, special problems).​