The clinical efficacy of mechlorethamine gel (Valchlor) as a maintenance therapy after low dose total skin electron beam therapy (TSEBT) for the treatment mycosis fungoides cutaneous T-cell lymphoma will be evaluated in this study. Subjects will be treated with low dose TSEBT (12 Gy total) over a period of two weeks. After a 30 day observation period and confirmation that their disease stage has been downgraded to IA or IB, subjects will use Valchlor as a maintenance therapy over the course of one year. The efficacy of Valchlor as a maintenance drug will be followed clinically through Modified Severity Weight Assessment Tool (mSWAT) and percent body surface area measurements (%BSA). Furthermore, subjects will be followed histopathologically through skin biopsies performed at the screening visit, immediately after observation period, one month after the start of the maintenance period, and twelve months after the start of the maintenance period (4 biopsies total).

Inclusion Criteria:

• 1. Male or Female
• ≥ 18 years of age
• Documentation of diagnosis as evidenced by one or more clinical features consistent with Mycosis Fungoides cutaneous T-Cell lymphoma
• Written informed consent obtained from subject or subject's legal representative and ability for subject to comply with requirements of the study
• Skin biopsy specimen of representative lesion obtained at screening of study and deemed diagnostic of Mycosis Fungoides by principal investigator
• Eligible, in the opinion of the investigator, for low dose TSEBT over the course of two weeks.
• Availability of subject to be observed for up to 18 months post-screening evaluation.
• Life Expectancy greater than 6 months

Exclusion Criteria:

• Pregnant or breast-feeding females
• Presence of a condition or abnormality that in the opinion of the investigator would compromise the safety of the patient or the quality of the data
• Patients diagnosed with Sezary Syndrome. Sezary Syndrome is equivalent to mycosis fungoides that develops to Stage IVA/B with B2 (high blood tumor burden) involvement, and as such requires a more aggressive treatment regimen than Valchlor or TSEBT.
• Patients who do not have their disease downgrade to stage IA or IB 30 days following low dose TSEBT.
• Underlying medical condition including unstable cardiac disease, or other serious illness that would impair the ability of the patient to undergo treatment
• Minimum 3 weeks since prior systematic treatment or phototherapy
• Decisionally-impaired individuals, prisoners, and vulnerable populations