Non–Langerhans Cell Histiocytoses: A Pictorial Review of Musculoskeletal Imaging Features

Presentation Format: Educational poster presentation.

Purpose or Learning Objective: (1) To describe the musculoskeletal imaging features of different non–Langerhans cell histiocytoses (N-LCH) on various imaging modalities using illustrations from our institution's cases; (2) to identify any pathognomonic or commonly reported findings; and (3) to describe the role of imaging in staging N-LCH.

Methods or Background: Histiocytoses are disorders characterized by abnormal accumulation and proliferation of histiocytic cells derived from members of the mononuclear phagocyte system. They are broadly categorized into Langerhans cell histiocytosis and N-LCH. N-LCH cases have different clinical presentations and imaging features than classical LCH, with only a few of the patients with N-LCH presenting with musculoskeletal soft tissue and osseous manifestations.

Results or Findings: Osseous involvement is almost a consistent feature of Erdheim-Chester disease, seen in 96% of cases. Radiographs typically show bilateral symmetrical diaphyseal long bone osteosclerosis, with relative sparing of the axial skeleton and epiphyses. Bone involvement on magnetic resonance imaging (MRI) is usually hypointense on T1-weighted and heterogeneously hyperintense on T2-weighted/short tau inversion recovery images and shows enhancement. In our experience, the pattern of marrow involvement can range from diffuse, geographic, nodular, or reticular, potentially the result from different stages of the disease process. Whole-body staging can be achieved with bone scintigraphy, fluorodeoxyglucose-positron emission tomography, or whole-body MRI.

Musculoskeletal Rosai-Dorfman disease presents as either a soft tissue mass with nonspecific MRI features or a predominantly lytic bone lesion of varying aggressiveness that can be associated with an extraosseous soft tissue mass. Consequently, the differential diagnosis is wide, and percutaneous needle biopsy is usually required for diagnosis.

Juvenile xanthogranuloma (JXG) presents as a cutaneous soft tissue mass or as a solitary nodule in the subcutaneous or deep soft tissues. MRI appearance of JXG lesions varies, with infiltrative and more nonaggressive appearances both described, as well as differing signal characteristics.

Conclusion: Only a few patients with N-LCH present with musculoskeletal features, and importantly no common overarching musculoskeletal imaging findings are observed in the described conditions. Due to their rarity, broad spectrum of clinical and musculoskeletal imaging findings, and mimicry to other conditions, diagnosing N-LCH can be challenging. Reporting radiologists should bear these entities in mind and include them when clinically relevant in their differential diagnosis.

Publication History

Article published online:
03 June 2021