Track: Case Reports

Abstract:

Although melanomas with spitzoid features (MSFs) and Spitz melanomas (SMs) share many histopathologic features, they are distinct entities, and differentiation has important prognostic and therapeutic implications. The WHO’s 2020 tumor classification guidelines define SMs as arising from kinase rearrangements or HRAS mutations, whereas MAPK pathway gene mutations such as NRAS or BRAF mutations are seen in MSFs. Thus, tumor genetic testing can help distinguish SMs and MSFs.

We discuss a 53-year-old female who presented with a growing red papule with eccentric hyperpigmentation and telangiectasias on her right ankle. Histopathologic examination revealed a compound melanocytic proliferation composed of large spindled-to-epithelioid melanocytes with prominent nucleoli. The junctional nests were elongated with admixed Kamino bodies. Dermal melanocytes were arranged in large nests with notable mitotic activity (up to 2/mm2). The melanocytes were immunoreactive with SOX10 and PRAME and negative for BRAF V600E and p16, concerning for SM versus MSF. Next-generation sequencing (NGS) was performed and identified NRAS, TERT, and CDKN2A mutations. The tumor was thus classified as an MSF (at least stage pT3b). The patient will undergo wide-local excision, sentinel lymph node biopsy, and evaluation for adjuvant immunotherapy.

MSFs have poor prognostication relative to SM, with shorter progression-free survival and higher prevalence of lymph node metastasis, more comparable to conventional melanomas. This case demonstrates the value of genetic testing in melanocytic lesions with spitzoid morphology, as the impact on diagnosis, prognosis, and treatment is significant. As NGS becomes more widely accessible, this will likely expedite informed and optimized treatment of these tumors.

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Alex Nguyen