Treatment of Cutaneous Metastases With Diphenylcyclopropenone (DPCP)

Inclusion Criteria: * male or female at least 18 years of age, up to 99 years of age * able to give verbal and written informed consent * clinically diagnosed cancer with multiple cutaneous metastases that are able to be biopsied. The subject may or may not be on concomitant cancer treatments/have internal metastases. * for women of childbearing potential (WOCBP) or in men whose partners may become pregnant, willingness to use an acceptable method of contraception to prevent pregnancy for the duration of the study (while receiving study medication and for one month following the last dose of study medication). Acceptable forms of contraception are listed in the informed consent form. * must have a negative urine pregnancy test (for WOCBP) * must be willing and able to have the therapy applied by the investigator, must be willing and able to self-apply the therapy, and must be willing and able to comply with study instructions and return for required clinic visits. * clinically diagnosed melanoma with multiple cutaneous metastasis that are able to be biopsied. The subject will be on concurrent PD-1 checkpoint inhibitor therapy (standard nivolumab or pembrolizumab, not on another clinical trial) and may or may not have internal metastasis. Exclusion Criteria: * subjects taking any of the following systemic or topical therapies within 4 weeks of enrollment: corticosteroids, immunosuppressants, and/or any other medications that may affect the outcome of the study * subjects who have active localized or systemic medical conditions that, in the opinion of the investigator, would preclude or make unsafe their participation in the study * subjects with any underlying diseases or dermatological conditions of the affected areas that require the use of interfering topical or systemic therapy * subjects who are nursing mothers, pregnant, or planning to become pregnant at anytime during the course of the study or within 30 days of study completion * subjects who are unable to comply with study procedures, communicate effectively, cooperate with the investigator, or are unable to understand the study * history, physical, social, or lab findings suggestive of any medical or psychological condition that would, in the opinion of the PI, make the candidate ineligible for the study * HIV positive as determined by self-reported history and/or a HIV point-of-care test at screening