Invasion level and lymph node metastasis are important prognostic factors in EMPD. In patients with in situ tumour, local tumour control is the major aim of treatment; however, wide surgical margins are not associated with a lower risk of local recurrence.

Sentinel lymph node biopsy was safe and feasible method and may have an important role in the management of extramammary Paget's disease with clinically N0 status. To establish the optimal management of inguinal lymph nodes in extramammary Paget's disease, additional studies in large number of patients are needed.

To examine for the genetic basis of metastatic progression in cutaneous melanoma, we have compared loss of heterozygosity (LOH) of several selected chromosome regions that are implicated in the initiation and progression of melanoma, and alterations of the p16INK4a gene in 14 pairs of primary tumor and synchronous or asynchronous metastasis excised from the same patients. The most frequent genetic alteration during metastatic progression detected was the loss of p16INK4a protein expression (four of 14 cases), whereas no somatic p16INK4a gene mutations were found in any primary or metastatic tumors. LOH analyses showed that most of the chromosome losses including 6q, 8p, 9p, 9q, and 18q were shared between primary tumors and their metastases. Nevertheless, LOH of 6q and 11q and LOH of 7q not detected in primary tumors were, respectively, observed in two lymph node metastases. These results suggest that loss of p16INK4a protein expression (but not p16INK4a gene mutation) and the losses of chromosome arms 6q, 7q, and 11q play an important role in the acquisition of metastatic potential in sporadic melanoma. Furthermore, comparison of genetic profiles between the primary tumor and its metastasis revealed in several cases that heterogenous tumor cell populations might already exist at the early stage of tumorigenesis and evolve independently in the primary tumor and its metastasis, strongly suggesting that metastatic progression of sporadic melanoma is not accounted for by a linear progression model.

In an attempt to examine whether the inactivation of p16INK4a is an important early event in the development of sporadic melanoma in vivo, we have systematically analysed 46 uncultured primary cutaneous melanomas. Loss of heterozygosity (LOH) of chromosome region 9p21-22 (where the p16INK4a resides) was detected in 11 tumours (24%) by PCR-based LOH analyses. Direct sequencing of all three exons of the p16INK4a gene in these 11 tumours revealed no somatic mutation although germline mutations which have not been reported previously as common polymorphisms were detected in two patients. Further sequencing analyses of the p16 INK4a protein, most likely due to homozygous deletion of the p16INK4a gene, was observed in 6 (15%) out of 39 evaluable cases by immunohistochemical analyses on frozen sections using two dierent anti-p16INK4a antibodies. The results show that inactivation of p16INK4a is not as frequent in primary melanoma as has been reported in cell lines, and warrant further search for another tumour suppressor on 9p21-22. This study also emphasizes the importance of examining uncultured primary tumours rather than cell lines to de®ne early events in tumorigenesis.

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