Eosinophils in metastatic melanoma.

Area of Science:

• Oncology
• Immunology
• Dermatopathology

Background:

• The role of tissue eosinophils in melanoma prognosis is not well-established.
• While lymphocytes are recognized for their role in anti-melanoma immunity, other immune cells like eosinophils may also be significant.

Purpose of the Study:

• To investigate the association between the presence of tissue eosinophils and the prognosis of patients with metastatic melanoma (MM).
• To explore the potential role of eosinophils in the immune response to melanoma, particularly in patients receiving immunotherapy.

Main Methods:

• Retrospective analysis of electronic medical records for patients diagnosed with metastatic melanoma between January 2011 and October 2022.
• Inclusion criteria required patients (age ≥18) to have at least one biopsy showing eosinophils in melanoma or melanocytic nevi.
• Data collected included patient demographics, histopathological features, AJCC staging, and peripheral blood eosinophilia (PBE).

Main Results:

• Seven patients met the inclusion criteria and received checkpoint inhibitor therapy for metastatic melanoma.
• Four of these seven patients exhibited prominent eosinophil infiltrates in their melanocytic nevi and/or melanomas.
• All patients with prominent eosinophils showed absent or less-than-predicted tumor progression, suggesting a favorable response.

Conclusions:

• In this small cohort, the presence of tissue eosinophils in patients with metastatic melanoma treated with immunotherapy was associated with a favorable treatment response.
• These findings suggest that eosinophils may play an underappreciated role in the host's immune response against melanoma.
• Further research is warranted to elucidate the specific mechanisms by which eosinophils influence melanoma progression and treatment outcomes.