In 1941, Sigmund S Greenbaum reviewed the literature on the reported cases of ulcerative pyodermas characterized by the special progression and the undermined borders. He notes that the term phagedena, used in France, was absent from American publications and discussions. Greenbaum proposes a classification of these phagedenic ulcers in primary, arising on normal or traumatized (accidentally or surgically) skin, and secondary, beginning as a venereal disease or an ecthyma.