Cutaneous acanthomas encompass many clinically distinct types. We describe a patient with multiple nodules on the skin of the upper limbs which were histologically diagnosed as large-cell acanthomas. Further analysis revealed, surprisingly, the presence of human papillomavirus (HPV) type 6 within these lesions. HPV type 6 should therefore be considered an important cofactor in the pathogenesis of large-cell acanthomas.

 A case of polypoid clear cell acanthoma on the scrotum.J Dermatol. 2004 Mar;31(3):236-8.

A red nodule appeared on the left side of the scrotum of a 37-year-old Japanese man and slowly grew for four years. When he first visited us, it was 5 mm in diameter, polypoid shaped, and had a smooth and slightly moist surface. Histologically, acanthosis, parakeratosis, and dilated blood vessels were seen in the upper dermis. In higher magnification, the thick epidermis consisted of tumor cells with slightly enlarged nuclei and pale cytoplasm, and neutrophils were also seen among the tumor cells. The cytoplasm of the tumor cells was stained with periodic-acid-Schiff (PAS), and the positive reaction was digested by diastase. There has been no previous report of polypoid clear cell acanthoma in Japan, and only a few reports from the rest of the world. In addition, clear cell acanthoma arising on the scrotum is particularly unusual.

Polypoid clear cell acanthoma of the scalp.Cutis. 2001 Feb;67(2):149-51.

Clear cell acanthoma (CCA) is a rare, benign epithelial tumor most frequently found on the lower extremities. Its clinical appearance may vary considerably, and cases of multiple lesions have been reported. The diagnosis is made by viewing the characteristic histologic features. This case describes an unusual scalp lesion that clinically and histologically shows unique polypoid features.