UV-induced multifocal cutaneous high-grade leiomyosarcoma.

Area of Science:

• Dermatology
• Oncology
• Pathology

Background:

• Cutaneous sarcomas typically present as solitary lesions.
• Multifocal presentation of cutaneous leiomyosarcoma (LMS) is exceptionally rare.
• This case involves an elderly male with a history of skin cancers.

Purpose of the Study:

• To report a unique case of multifocal cutaneous high-grade leiomyosarcoma (LMS).
• To highlight unusual features including multifocal disease, UV gene signature, and PD-1 expression.
• To investigate the therapeutic response to radiation and immunotherapy.

Main Methods:

• Histopathological examination and immunohistochemistry (desmin, PD-1).
• Gene expression profiling for UV signature analysis.
• Clinical assessment of response to radiation therapy and pembrolizumab.

Main Results:

• Biopsy confirmed high-grade desmin-positive LMS with 99% PD-1 expression.
• Gene expression profiling revealed a UV gene signature.
• Radiation therapy showed initial response, followed by development of new nodules.
• Pembrolizumab led to rapid resolution of remaining cutaneous nodules.

Conclusions:

• This case demonstrates unusual multifocal presentation of cutaneous high-grade LMS.
• A UV gene signature may be associated with this rare malignancy.
• High-grade cutaneous LMS expressing PD-1 shows significant responsiveness to anti-PD-1 therapy.