Mitotically active deep juvenile xanthogranuloma.

Area of Science:

• Dermatopathology
• Histiocytic Tumors
• Soft Tissue Oncology

Background:

• Juvenile xanthogranuloma (JXG) is a rare histiocytic tumor typically affecting neonates and children.
• Deep subcutaneous and intramuscular JXG are uncommon, and a mitotically active variant is exceedingly rare, with only one prior case reported.
• Adult presentation of JXG, especially deep intramuscular forms, is exceptionally rare.

Observation:

• A case of mitotically active intramuscular juvenile xanthogranuloma in the upper arm of a 28-year-old woman is presented.
• Fine-needle aspiration biopsy was performed, with differential diagnoses including deep malignant melanoma and alveolar rhabdomyosarcoma.
• The tumor was surgically excised, and the patient remained disease-free one year post-operation.

Findings:

• The study emphasizes the critical role of cytologic-histologic correlation in diagnosing rare JXG variants.
• Differential diagnoses considered included atypical diffuse giant cell tumor and rare leiomyosarcoma subtypes.
• Successful surgical excision led to a favorable outcome for the patient.

Implications:

• This case expands the known spectrum of juvenile xanthogranuloma, particularly its rare mitotically active and deep intramuscular presentations in adults.
• Accurate histopathological diagnosis is crucial to differentiate JXG from aggressive soft tissue malignancies.
• Effective management strategies for rare JXG variants require careful consideration of clinical, cytologic, and histologic findings.