17. Is differentiated VIN a cancer precursor in women with vulval lichen sclerosus?

Approximately 60% of squamous cell carcinomas of the vulva (SCCV) arise in a background of lichen sclerosus (LS), and 30% in HPV-related ‘undifferentiated’ VIN. The pathogenesis of cancer arising in LS is unclear, occurring in less than 5% of women. In some women, an additional histological finding of differentiated VIN (DVIN, HPV negative) may be recognised in the skin adjacent to an invasive tumour, only rarely prior to invasion. To evaluate the histology of vulval biopsies or excised specimens in women with LS who developed invasive cancer at least 6 months later. The clinical records and histology of 206 women presenting to the Auckland Regional Gynaecological Cancer Unit (National Women’s Hospital) between 1990 and 2007 with SCCV were reviewed retrospectively. Invasive SCCV was found in a background of LS in 103 women (50%). Sixteen of these women (16%) had had a biopsy at least 6 months before presenting with their index vulval tumour. In 9 cases (56%) DVIN was demonstrated on biopsy, and in 7 cases LS alone. A second group of 17 women previously treated for SCCV presented with 26 subsequent ‘new’ cancers at least 6 months following complete excision of the earlier tumour. Review of the histology of the 26 tumours revealed incompletely excised DVIN in 12 (46%). This study has demonstrated DVIN in previous biopsies or excised specimens in a significant proportion of women in whom invasive carcinoma has developed in a background of LS. These findings suggest DVIN is a cancer precursor in women with vulval LS.