18F-FDG PET/CT Findings in an Infant With Multisystem ALK-Positive Histiocytosis

Area of Science:

• Pediatric Oncology
• Histiocytic Neoplasms
• Molecular Pathology

Background:

• Anaplastic Lymphoma Kinase-positive (ALK) histiocytosis is a rare histiocytic neoplasm primarily affecting infants and children.
• This condition can manifest as single-system or multisystem disease, frequently involving the central nervous system (CNS).
• Published imaging findings, particularly using 18F-FDG PET/CT, are limited and often focus on CNS or localized extranodal disease.

Purpose of the Study:

• To describe the comprehensive imaging spectrum of disseminated ALK-positive histiocytosis.
• To illustrate extensive multi-organ and genital tract involvement in a pediatric patient.
• To expand the understanding of 18F-FDG PET/CT findings in this rare neoplasm.

Main Methods:

• Case report of a 5-month-old female infant with pancytopenia and hepatosplenomegaly.
• Whole-body 18F-FDG PET/CT imaging was performed to assess disease extent.
• Detailed analysis of imaging findings across multiple organ systems.

Main Results:

• The patient presented with pancytopenia and hepatosplenomegaly.
• Whole-body 18F-FDG PET/CT revealed intensely FDG-avid disseminated disease.
• Involvement was observed in the brain, parapharyngeal/skull-base, lungs, liver, pancreas, kidneys, cervix, uterus, vagina, vulva, soft tissues, muscle, spinal canal, and skeleton.

Conclusions:

• This case demonstrates extensive multiorgan and genital tract involvement in ALK-positive histiocytosis.
• 18F-FDG PET/CT is a valuable tool for assessing the full extent of this rare pediatric neoplasm.
• The imaging findings expand the known spectrum of ALK-positive histiocytosis, emphasizing its potential for widespread dissemination.