An additional analysis showed a notable difference in incidence rates over the 15-year period studied, depending on age. In children aged 0-9 years, the annual incidence rate held roughly steady at just under 2 cases per million throughout the 15 years. But among adolescents, the rate fell over time, from about 10-12 cases per million during 2000-2004 to about 5-7 cases per million during 2010-2014. In 2001, the rate was about 11 cases per million, and in 2013, the rate was about 6 cases per million. This contrasts with the adult rate, which has “risen rapidly over the past 30 years,” according to the American Cancer Society’s 2018 report.
The SEER data also showed that distribution of melanoma histologic types differed by age. Among adolescents the most common identified form was “superficial spreading,” in 32%, with nodular in 6%, mixed epithelioid and spindle cell in 2%, and “not otherwise specified” in 54%. In children, the most commonly identified form was mixed epithelioid and spindle cell, in 10%, followed by nodular in 9%, and superficial spreading in 9%, with 63% not otherwise specified.
SOURCE: Kelm RC et al. AAD 18, Abstract 6722.