Frequent activating HRAS mutations in trichilemmoma

Abstract

C and c.182A>G mutations were observed in 17 and three tumours, respectively. Of the 12 NS-related tumours, 11 (92%) harboured the HRAS c.37G>C substitution. Of the 15 sporadic tumours, nine (60%) harboured HRAS mutations, including six c.37G>C and three c.182A>G. An HRAS c.182A>G mutation was observed only in sporadic tumours. No mutations were observed in the other genes that were tested. Conclusions The high frequency of HRAS activating mutations, including the c.182A>G substitution, which was rather rare in NS, suggests that most trichilemmomas are authentic neoplasms. What's already known about this topic? Virtually all cases of naevus sebaceus (NS) are caused by postzygotic HRAS or KRAS mutations. Trichilemmoma is among the most common secondary tumours associated with NS. What does this study add? Sporadic trichilemmomas frequently harbour activating HRAS mutations, including the c.182A>G substitution, which is rather rare in NS. The high frequency of activating HRAS mutations suggests that most trichilemmomas are authentic neoplasms.