Brentuximab Vedotin (SGN-35) in Patients With Mycosis Fungoides With Variable CD30 Expression Level

Inclusion Criteria: * Biopsy-proven MF/SS, stage IB-IVB, and failed one standard systemic therapy. Skin biopsy must be within 3 months of beginning study medication * At least the following wash-out from prior treatments: * ≥ 3 weeks for local radiation therapy, systemic cytotoxic anticancer therapy, treatment with other anti-cancer investigational agents (including monoclonal antibody) * \> 3 weeks for retinoids, interferons, vorinostat, romidepsin, denileukin diftitox and phototherapy * \> 2 wks for topical therapy (including topical steroid, retinoid, nitrogen mustard, or imiquimod) * At least 18 years of age * ECOG performance status of ≤ 2 * Must be able to commit to study schedule * Absolute neutrophil count (ANC) ≥ 1000/uL * Platelets ≥ 50,000/uL * Bilirubin ≤ 2X upper limit of normal (ULN) (EXCEPTION: Gilbert's disease ≤ 3X ULN) * Serum creatinine ≤ 2X ULN * Alanine aminotransferase (ALT) ≤ 3X ULN * Aspartate aminotransferase (AST) ≤ 3X ULN * Negative serum beta-HCG pregnancy test result within 7 days of first treatment, if a woman of childbearing potential * Ability to understand and the willingness to sign a written informed consent document Exclusion Criteria: * Mycosis fungoides (MF) with limited disease (stage IA) or central nervous system (CNS) disease * Systemic or topical concomitant corticosteroid use for treatment of skin disease (EXCEPTION: Oral prednisone allowed at ≤ 10 mg/day) * Known Grade 3 or higher (per NCI CTCAE v4.0 criteria) active systemic or cutaneous viral, bacterial, or fungal infection * Known to be Hepatitis B or Hepatitis C antibody positive * HIV-positive with have a measurable viral load while on antiretroviral medication * Known hypersensitivity to recombinant proteins or any excipient contained in the drug formulation. * History of other malignancies during the past 3 years (EXCEPTIONS: non-melanoma skin cancer; curatively treated localized prostate cancer; curatively treated localized breast cancer; resected thyroid cancer; cervical intraepithelial neoplasia; or cervical carcinoma in situ on biopsy). * Pregnant * Breastfeeding * Congestive heart failure, Class III or IV, by New York Heart Association (NYHA) criteria. * Any serious underlying medical condition that would impair subject's ability to receive or tolerate the planned treatment. * Dementia or altered mental status that would preclude subject's understanding and rendering of informed consent.