Ectopic extramammary Paget's disease: case report and literature review

Extramammary Paget's disease that occurs in non-apocrine-bearing regions is referred to as ectopic and has been rarely reported. A 62-year-old man presented with a slowly progressive, asymptomatic light-brown plaque on his back. Histopathological examination revealed the presence of large pale cells with prominent nuclei, which proliferated diffusely and focally in the epidermis. Immuno-histochemically the tumour cells were positive for CK7, GCDFP-15, CEA, and p63. Based on these findings, we diagnosed the tumour as ectopic extramammary Paget's disease. We reviewed the English and Japanese literature and found 29 previously reported cases of ectopic extramammary Paget's disease, including our case, with a predominance of occurrence in the Asian population. The germinative milk line is known to be a possible site where extramammary Paget's disease occurs. Like-wise, some germinative apocrine-differentiating cells might exist on the trunk preferentially in Asians. Attention should be paid to the development of ectopic as well as triple or quadruple EMPD in Asians.