Intraneural granular cell tumor: Histologic spectrum and histogenetic implication

Area of Science:

• Neuropathology
• Soft Tissue Tumors
• Histology

Background:

• Granular cell tumors (GCTs) are rare, with most occurring in extraneural sites.
• Intraneural GCTs are exceptionally uncommon, with only six prior case reports.
• The exact origin of GCTs remains debated, though a neural origin is often suggested.

Observation:

• A unique case of intraneural GCT is presented, notable for the longest symptom duration, largest tumor size, and associated motor dysfunction.
• The patient exhibited significant muscle atrophy and fatty infiltration secondary to the tumor.
• Histologic examination revealed a wide spectrum of GCT variants, including benign, plexiform, hybrid, and malignant forms, alongside perineurioma.

Findings:

• The immunophenotype of GCTs is not identical to schwannomas.
• Ultrastructural studies provide further evidence regarding GCT origins.
• The findings support the hypothesis that GCTs originate from undifferentiated mesenchymal cells with partial schwannian differentiation.

Implications:

• This mesenchymal origin theory better accounts for the diverse topographic distribution of GCTs, both extraneural and intraneural.
• Understanding the origin of GCTs is crucial for accurate diagnosis and treatment planning.
• Further research into the cellular origins of GCTs may reveal new therapeutic targets.