We report two cases of Dowling-Degos' disease, one affecting the vulvovaginal semimucose, and one associated to a terminal malignant neoplasia. We remark the importance of this knowledge in order to distinguish it from malignant acanthosis nigricans or other patterns of melanosis or lentiginosis when located within mucose or semimucose, specially at the genitals. All cases associated to malignant neoplasia described are emphasized. However Dowling-Degos' disease is considered to be a nonparaneoplasic genodermatoses, this association should be taken into account.