Clinicians should not ‘shy away’ from a Spitz neoplasm diagnosis in adults

Key takeaways:

• Spitz neoplasms occurred most frequently between ages 31 and 40 years (22.4%).
• 20% of all Spitz neoplasm diagnoses made with next-generation sequencing were for patients aged 50 to 80 years.

The dawning of genomic testing has shown that Spitz neoplasm cases occur at equal rates among children and adults, which should prompt clinicians to diagnose Spitz neoplasms more confidently among older patients, according to a study.

“The discovery of genomic fusions as the primary genomic drivers in Spitz neoplasms is a break-through discovery deeply impacting our understanding of this class of melanocytic neoplasms,” Michael Hagstrom, BA, of the department of dermatology at the Feinberg School of Medicine at Northwestern University, and colleagues wrote. “Much of the epidemiologic data regarding Spitz neoplasms have been collected and reported prior to the advent of these critical discoveries. Hence, we believe there is a need for reappraisal of their epidemiology.”

Hagstrom and colleagues reassessed the epidemiology of Spitz neoplasms using next-generation sequencing (NGS). The study included 54,814 non-Spitz neoplasms and 1,260 Spitz neoplasms, the latter group including 286 Spitz neoplasms verified by NGS.

Results showed that the relative proportion of Spitz neoplasms was highest in the first 4 decades of life, with the highest rate of 22.4% occurring in patients aged 31 to 40 years. This was followed by 20.9% of patients aged 0 to 10 years, 19.2% of those aged 21 to 30 years, 15.7% of those aged 11 to 20 years and 12.3% of those aged 41 to 50 years.

Occurrences dropped significantly after the fifth decade, with only 5.5% of cases occurring between age 51 to 60 years and 3% between age 61 to 70 years. Additionally, all occurrences after the age 71 years were less than 1%.

Previous studies have shown that Spitz neoplasms mainly occur in childhood and not in adulthood. However, these findings support the authors’ hypothesis that the rate of Spitz neoplasms is similar between childhood and adulthood before the fifth decade.

The authors explained that Spitz neoplasms appeared to be more frequent in younger patients simply because they comprised a larger percentage of the total number of melanocytic neoplasms from that age group. In fact, the proportion of Spitz neoplasms relative to the total number of melanocytic neoplasms in the first decade of life was nearly 40% compared with only 2% in the fourth decade of life, according to the study.

“This is a conceptually important finding informing clinicians and pathologists that while they should be aware that epidemiologically a biopsied melanocytic neoplasm in adult patients is less likely to be a Spitz neoplasm, the overall frequency at which Spitz neoplasms occur in adults before the fifth decade is relatively similar to that in childhood,” the authors wrote. “Therefore, if Spitz neoplasm is the best morphologic fit, they should not shy away from that diagnosis.”

Additionally, of all the diagnoses made with NGS, almost 20% were for patients aged between 50 and 80 years — a much higher rate of success compared with the approximately 8% of diagnoses made without NGS. This suggests that NSG may be particularly helpful in guiding clinicians to accurately diagnosis Spitz neoplasms and avoid melanoma overdiagnosis in older adults, according to the authors.