heterozygous for this mutation, which was not detected in 50 control chromosomes (Fig. 3a-e).Since Urbach and Wiethe's publication in 1929, 1 over 250 cases of lipoid proteinosis have been described. To the best of our knowledge, only six families with lipoid proteinosis have been reported in China. Among them, only two families had been identified mutations of the ECM1 gene. 5,6 Interestingly, one of the family had a compound heterozygous C220G in exon 6 and R476X in exon 10 mutation, and the other had the homozygous C220G mutation in exon 6 which is same as we reported. As far as we know, the ECM1 mutation database contains few recurrent mutations; most are specific to individual families. Within South Africa, however, there is evidence for propagation of a common ancestral allele harbouring the mutation p.Q276X in exon 7. 2 To date, over 30 cases of lipoid proteinosis affecting individuals have all been shown to be homozygous for this mutation. 7 Moreover, no other pathogenic mutation in ECM1 has been identified in the South African population. These three Chinese families are not related, but they all have the mutation C220G in exon 6; this amino acid substitution has not been demonstrated in any other countries individuals with lipoid proteinosis, so we speculate this mutation may represent an ancestral allele within Chinese population. We recommend initial screening for this sequence variant in new cases of lipoid proteinosis in China. If C202G is not detected, direct sequencing of exons 6 and 7 of ECM1 should then follow, as over 60% of the other mutations detected have occurred in these two exons. 4

EditorVerrucous carcinoma, first reported by Ackerman in 1948, 1 is a distinct variant of differentiated squamous cell carcinoma with low-grade malignancy, slow growth and no metastatic potential. The oral cavity is the most common site of this tumour. The ages range from 50 to 80 years with a male predominance. In 1960, Rock and Fisher 2 described a similar lesion, which they named oral florid papillomatosis. Clinically warty tumours with a grey-white, deeply cleaved surface are detected. Histology reveals a sharply circumscribed tumour, with marked papillomatosis and overlying hyperkeratosis. Broad bulbous acanthotic projections of epidermis may extend deep into the stroma. An associated dense inflammatory cell infiltrate is often present. As with other forms of verrucous carcinoma, little atypia is present in most cases. The association of carcinogen exposure with oral cancer has been reported. The sources of the carcinogens include tobacco, alcohol, marijuana or cigarette smoking and betel nuts. 3 A 76-year-old woman presented with a 30-year history of a vulgar penfigous treated with decreasing doses of meprednisone, actually with 4 mg. Three years later, she was diagnosed and surgically treated for a clear cell renal carcinoma and a tubulovillous adenoma of the colon with high grade dysplasia. She was also a cigarette smoker for 30 years. On physical examination, a 10 · 3 cm verrucous erythematous tumour with areas of leukoplaquia was present on the top gum. Two surgical biopsies were performed in different areas of the lesion (Fig. 1a). Histological examination showed and exophytic growth of keratinocytes. Hyperkeratosis and acanthosis were accompanied by a marked upward elongation of dermal papillae. At high-power magnifica-