A 69-year-old Japanese woman presented with multiple, erythematous, keratotic plaques distributed on her right breast, right shoulder, and left cubital fossa. The lesions varied in size from 5 mm to 6 cm. The patient had first noticed a small area of primary erythema on her left cubital fossa at the age of 18 years. The number and size of the lesions had increased for 50 years. A black nodule appeared on the plaque on the right breast 3 years ago and enlarged to 5 cm in diameter (Fig. 1A). Figure 1. (a) Erythematous plaques varying in size distributed on both breasts. The biggest plaque contained hyperkeratotic tumor. The black nodule appeared on the plaque of the right breast. (b) Six months after black tumor removal, hypertrophic change was noted on the scar. Topical application of vitamin D3 analog caused regression in size and elevation of the largest keratotic plaque, and a decrease in hyperkeratosis of the other eruptions Download figure to PowerPoint The patient was born to healthy nonconsanguineous parents. She grew up in the center of Kanazawa city, Ishikawa prefecture, central area of Japan, and had no history of arsenic exposure or outdoor work. She had no past history of repeated infectious diseases and no family history of recalcitrant warts. A tuberculin test gave an area of induration, 1.0 cm in diameter, in 48 h. The black tumor on the breast was surgically removed with a margin of uninvolved skin. Biopsies from lesions on the right breast (hyperkeratotic erythematous plaque) and left cubital fossa (small erythema without hyperkeratosis) were performed. Microscopic examination of hematoxylin and eosin-stained sections from all specimens showed similar findings. Nests of anaplastic keratinocytes were present in an intraepidermal epithelioma pattern within the expanded epidermal layer. A superficial dermal inflammatory cell infiltrate was also observed. There were irregular masses of epidermal cells that proliferated downwards into the dermis. Atypical mitotic figures, multinucleated keratinocytes, and individual cell keratinization were also observed (Fig. 2). Large clear keratinocytes, specific for epidermodysplasia verruciformis, were not found. Anti-papillomavirus antibody (Dako, Japan) did not react with any of the specimens. A histologic diagnosis of Bowen's disease (BD) (squamous cell carcinoma in situ) was made. Figure 2. In the biopsy specimen from the erythematous plaque on the breast, there were irregular masses of epidermal cells that showed atypical mitotic figures, multinucleation, and individual cell keratinization (hematoxylin and eosin stain, × 100) Download figure to PowerPoint Because the other lesions were distributed diffusely and the patient refused surgical treatment, oral etretinate (10 mg/day) was started; however, dryness of the lips and a burning sensation of the involved skin were intolerable. Therefore, topical application of 1-α,24-dihydroxyvitamin D3 ointment (tacalcitol, Bonalpha™) was chosen as alternative treatment. This vitamin D3 analog provided some relief to the redness and hyperkeratosis of all the erythematous plaques. Moreover, the largest keratotic plaque showed a remarkable regression in size and elevation 6 months later (Fig. 1B). No new tumors or erythematous plaques have been found for 3 years since vitamin D3 analog treatment started. DNA from two frozen tissue samples (black, smooth-surfaced tumor and hyperkeratotic erythematous plaque) was extracted by a standard proteinase K/phenol–chloroform–isoamyl alcohol extraction technique. Samples of total cellular DNA (100 ng) were amplified by polymerase chain reaction (PCR) using four sets of degenerate primers (F10/B5, F12/B5, CP66/CP69, and GP5/GP6) in the highly conserved region of the L1 open reading frame of papillomaviruses (Shamanin V, Delius H, de Villiers EM. Development of a broad spectrum PCR assay for papillomaviruses and its application in screening lung cancer biopsies. J Gen Virol 1994; 75: 1149–1156; Shamanin V, zur Hausen H, Lavergne D, et al. Human papillomavirus infections in nonmelanoma skin cancers from renal transplant recipients and nonimmunosuppressed patients. J Natl Cancer Inst 1996; 88: 802–811; de Villiers EM, Lavergne D, McLaren K, Benton EC. Prevailing papillomavirus types in non-melanoma carcinomas of the skin in renal allograft recipients. Int J Cancer 1997; 73: 356–361). For each set of reactions, negative controls for reagents and DNA were included and processed in the same way as the lesional samples throughout all PCR steps. Two human papillomavirus (HPV) plasmids (0.01 pg) containing the genotypes HPV-4 and HPV-6 served as positive controls. PCR products (10 µL) were subjected to 2% agarose gel electrophoresis. Three sets of primers (F10/B5, F12/B5, and CP66/CP69) amplified HPV-specific DNA fragments in both DNA samples from the BD lesion (Fig. 3). The recombinant plasmids harboring the insert of the amplified DNA were sequenced. The sequences obtained were compared with the available HPV sequences in GenBank (National Center for Biotechnology Information, National Institutes of Health), using the husar software package (Deutsches Krebsforschungszentrum). The sequences of all plasmids corresponded to the L1 portion of HPV-5, except for a few nucleotide substitutions. Figure 3. Results of polymerase chain reaction: 650-bp bands appear in lanes 1, 3, and 4 (human papillomavirus, HPV). Larger sized bands are nonspecific products (NS). Lane M, size marker. Lane 1, DNA extracted from HPV-6 (positive control). Lane 2, DNA extracted from human placenta. Lane 3, DNA extracted from black tumor. Lane 4, DNA extracted from hyperkeratotic plaque Download figure to PowerPoint