Multiple Langerhans cell nodules in an incidental thymectomy

Area of Science:

• Pediatric Pathology
• Immunohistochemistry
• Histopathology

Background:

• Langerhans cell histiocytosis (LCH) is a rare clonal myeloid neoplasm.
• Isolated thymic LCH is exceptionally uncommon, with few childhood cases reported.
• Previous reports describe massive thymic infiltration rather than subtle nodules.

Observation:

• A case of an 11-month-old infant with thymic LCH nodules incidentally found post-thymectomy for tetralogy of Fallot repair.
• The observed nodules were small and subtle, differing from previously described massive thymic LCH.
• Histologic review of 22 incidental thymectomy specimens from cardiac surgery revealed no similar LCH aggregates.

Findings:

• The index patient presented with multiple small Langerhans cell aggregates in the thymus.
• No similar Langerhans cell aggregates were identified in 22 control thymectomy specimens.
• The thymic LCH pattern in this infant more closely resembles that seen in adult myasthenia gravis patients.

Implications:

• This finding questions whether subtle thymic LCH aggregates may be under-recognized, particularly in incidental thymectomy specimens.
• Further investigation is warranted to determine the prevalence and significance of incidental thymic LCH.
• The distinct presentation suggests potential differences in LCH pathogenesis or presentation based on age and clinical context.