Specific features associated with uncommon variants of cutaneous melanoma

Uncommon variants of cutaneous melanoma do not have the classic clinical appearance and dermoscopic criteria for diagnosis, according to a systematic review published in JAMA Dermatology.

“This systematic review described four melanoma variants in the current World Health Organization classification (desmoplastic, nevoid, spitzoid and animal-type) as well as six other melanoma variants (amelanotic, balloon cell, follicular, nested, dermal and verrucous),” Riccardo Pampena, MD, of the center of high technology oncology diagnostics health unit at Reggio Emilia in Modena, Italy, and colleagues wrote. “The results of the present systematic review showed that uncommon variants of melanoma more frequently appeared in women than in men, with a global mean age of 58 years.”

Researchers conducted a two-step systematic literature search in PubMed, Embase and Cochrane Central Register of Controlled Trials databases until November 2018 to define clinical or histologic variants of cutaneous melanoma. Following this search, researchers individually investigated each identified uncommon or rare variant in the same databases and searched for histopathologic confirmed cases of the same uncommon melanoma variants in an institutional database from January 2012 to September 2019.

Sixty-two articles were included in this review, comprising 433 melanoma cases; 56 cases from the institution’s database brought the total to 489 cases. Spitzoid melanoma occurred in younger patients than the other histologic variants. Spitzoid melanoma and verrucous and nested variants mainly occurred on the lower limbs. Animal-type, pigmented epithelioid melanocytoma, desmoplastic and follicular melanomas occurred on the head and neck. Balloon cell and nevoid melanomas occurred on the trunk, and amelanotic melanoma occurred on acral skin. A majority of lesions (74.7%) were palpable, and 57.9% were amelanotic.

“This overview may help clinicians recognize these uncommon and tricky-to-diagnose variants that frequently simulate other benign or malignant skin lesions,” the researchers wrote.

“This systematic review also highlights the complex and evolving nature of melanoma classification, which has traditionally been based on histopathologic and clinical features but more recently also incorporates genomic alterations,” Daniel M. Miller, MD, and Karolyn A. Wanat, MD, wrote in an accompanying editorial.

Additional tools to diagnose these uncommon melanomas are important for clinicians to recognize cases with unusual clinicopathologic features.

“Melanoma diagnosis and classification is a rapidly evolving landscape, as multiple new genomic pathways to malignant neoplasms are currently being identified,” Miller and Wanat wrote. “Improved recognition of the clinical, histopathologic and dermoscopic features of rare melanoma variants will hopefully ultimately lead to their improved classification and prognostication.” – by Erin T. Welsh

Disclosures: The authors report no relevant financial disclosures.