Two patients had granuloma annulare which appeared as small nodular lesions with central umbilication on the hands and margins of the fingers. Histopathologic study showed perforation of the epidermis and release of the abnormal necrobiotic material transepithelially. This type of granuloma annulare is distinctive both clinically and histologically and is probably more common than presently recognized.
Owens DW, Freeman RG. Perforating Granuloma Annulare. Arch Dermatol. 1971;103(1):64-67. doi:10.1001/archderm.1971.04000130066010