Histopathologic and Immunophenotypic Properties of Primary Cutaneous Large Cell Neuroendocrine Carcinomas

Area of Science:

• Dermatopathology
• Oncology
• Histopathology

Background:

• Cutaneous large cell neuroendocrine carcinoma (LCNEC) is a rare malignancy with limited understanding.
• Primary cutaneous LCNEC (PCLCNEC) requires further characterization for accurate diagnosis and management.

Purpose of the Study:

• To describe the clinicopathological characteristics of six PCLCNEC cases.
• To evaluate the diagnostic features and immunohistochemical profiles of PCLCNEC.
• To contribute insights into the potential distinction of PCLCNEC as a unique cutaneous entity.

Main Methods:

• Retrospective review of PCLCNEC cases from January 2017 to May 2025.
• Analysis of patient demographics, histopathologic features, and immunohistochemical profiles.
• Inclusion of Merkel cell polyoma virus (MCPyV) antigenicity in the analysis.

Main Results:

• PCLCNEC occurred in elderly white patients, presenting as rapidly progressing nodules on sun-exposed skin.
• Histology showed infiltrative growth with neuroendocrine features; tumors were CK7+, neuroendocrine markers+, and negative for MCPyV, CK20, TTF1.
• Five of six patients achieved no evidence of disease after wide local excision.

Conclusions:

• The clinicopathological and immunophenotypic findings provide valuable insights into PCLCNEC characterization and diagnosis.
• The data support further investigation into PCLCNEC as a distinct cutaneous entity.
• Understanding PCLCNEC morphology and immunophenotype is crucial for its recognition and management.