A case of multiple eccrine syringofibroadenoma with palmoplantar keratoderma

An 85-year-old woman had presented scaly erythema on her palms and keratoderma on her soles for 60 years. Seven years previously, she had undergone surgical resection of squamous cell carcinoma (SCC) on her left palm. Scaly erythema was observed on both her palms and keratoderma was observed on her soles, prompting a diagnosis of palmoplantar eczema. Biopsies from the lesions of the palms and soles showed thin cords of epithelium that elongated downward and anastomosed with one another to form a lattice-like pattern including eccrine ducts in several areas. These findings led to a final diagnosis of multiple eccrine syringofibroadenoma (ESFA). Since the prior surgical specimen of SCC was accompanied by similar findings of ESFA, the malignant transformation of ESFA was considered to have caused the development of SCC. Although ESFA usually presents as a solitary, large hyperkeratotic nodule appearing on the extremities, it sometimes presents as palmoplantar keratoderma. Owing to a lack of clear demarcation, we treated this case with topical highly potent steroids and narrow-band ultraviolet B irradiation without particularly satisfactory effects. Because of the risk of malignant transformation, regular follow-up and close observation are warranted.