Cellular Dermatofibroma Harboring a Novel MYADM::PRKCG Gene Fusion: A Case Report

Area of Science:

• Oncology
• Dermatopathology
• Molecular Pathology

Background:

• Dermatofibroma (DF) classification is challenging due to morphologic variability and limited immunohistochemical specificity.
• Recent advances in molecular techniques have identified recurrent genetic alterations in cutaneous mesenchymal tumors, aiding diagnosis.
• Protein kinase C gene fusions have been recently described in dermatofibroma.

Purpose of the Study:

• To report a novel case of dermatofibroma with a unique genetic fusion.
• To highlight the utility of molecular techniques in diagnosing challenging cutaneous neoplasms.
• To expand the understanding of the molecular landscape of dermatofibroma.

Main Methods:

• Histopathological examination of the cutaneous lesion.
• Immunohistochemical staining for smooth muscle actin and desmin.
• Targeted RNA sequencing to identify fusion transcripts.

Main Results:

• A cellular, pseudoangiomatous dermatofibroma was identified in a 56-year-old man.
• Histology showed high cellularity, prominent vascularity, and focal smooth muscle actin/desmin positivity, mimicking other neoplasms.
• Targeted RNA sequencing revealed a novel in-frame MYADM::PRKCG fusion transcript.

Conclusions:

• The identified MYADM::PRKCG fusion provides a definitive molecular classification for this dermatofibroma case.
• This represents the first description of a MYADM::PRKCG rearrangement in dermatofibroma.
• Molecular profiling is crucial for accurate diagnosis and classification of challenging cutaneous mesenchymal tumors.