The role of 2-[18F]FDG PET/CT in Erdheim-Chester disease

OBJECTIVE

To analyze the body distribution of Erdheim-Chester disease (ECD) and determine the utility of 2-[18 F]FDG PET/CT compared to other imaging techniques. Additionally, to assess the aggressiveness and extent of the disease based on the presence/absence of the BRAFV600E mutation.

MATERIALS AND METHODS

The 2-[18F]FDG-PET/CT scans of all patients diagnosed with ECD between 2008 and 2021 were reviewed, including 19 patients. The affected territories were classified as detectable by PET/CT or detectable only by other imaging techniques (bone scintigraphy, contrast-enhanced CT, or MRI). Descriptive analysis and correlation of the BRAF mutation with the affected organs and maximum SUV were performed using the Student's t-test.

RESULTS

Out of the 19 patients (14 males; mean age 60.3 years), 11 had the BRAFV600E mutation. A total of 127 territories (64 organ-systems) affected were identified using different imaging modalities, of which 112 were detected by PET/CT, and an additional 15 territories were solely identified by cerebral and cardiac MRI. The presence of BRAFV600E mutation was associated with greater organ involvement (p < 0.05) without differences in SUVmax (p > 0.05).

CONCLUSION

2-[18F]FDG PET/CT is a highly effective diagnostic tool in patients with ECD, detecting the majority of affected territories. MRI was the only imaging modality with additional findings in territories showing high physiological uptake of 2-[18F]FDG (cerebral and cardiac). The presence of the BRAFV600E mutation correlated with a higher extent of the disease.

Isolated Bone Marrow Non-Langerhans Cell Histiocytosis Preceding RUNX1-Mutated Acute Myeloid Leukemia: Case Report and Literature Review

OBJECTIVES

The prevalence of concomitant myeloid neoplasms was recently reported to be unexpectedly high among adults without non-Langerhans cell histiocytosis (non-LCH); however, the coexistence of non-LCH with RUNX1 genetic aberration has not been reported previously.

METHODS

Herein, we report a 23-year-old woman with severe pancytopenia diagnosed with non-LCH following presentation with pancytopenia and marrow examination showing histiocytosis positive for CD45, CD68, CD136, and lysozyme but negative for CD1a, langerin, and S100.

RESULTS

Whole-exome sequencing showed RUNX1 mutation and NF1 mutation. In the ensuing 6 months, she developed hepatosplenomegaly, and repeat bone marrow evaluation was diagnostic of acute myeloid leukemia (AML). Repeat mutational analysis showed again presence of RUNX1 mutation. She underwent induction therapy but died of septic shock.

CONCLUSIONS

The demonstration of RUNX1 mutation in both non-LCH and AML bone marrow specimens at differing time points is suggestive of a biologic association of both distinct disease entities.