Clinical History
A 41-year-old patient who presented with recurrent headache and bilateral knee pain for the last 2 years. A brain MRI was performed and showed a large soft tissue falcotentorial mass. This lesion was initially treated with radiotherapy without clinical or radiological response.
Imaging Findings
1. Brain MRI findings:
Large soft tissue mass involving the tentorium and falx cerebri, markedly hypointense on T2-weighted image and mildly hyperintense on T1-WI. (Fig.1, 2)
The lesion originated from the posterior falx cerebri extending to the tentorium, showing an intense homogeneous enhancement (Fig. 3a) and infiltrating the vein of Galen, the straight sinus and the medial aspect of both transverse sinus (Fig. 3b, c)
Soft-tissue masses engulfing the right optic nerve and on the posterolateral aspect of the left globe. These lesions were markedly hypointense on T2WI and showed an intense contrast uptake (Fig.1d, e; Fig.3d)
2. X-ray films
Plain films of the legs were performed due to bilateral knee pain: Medullary osteosclerosis, predominantly in the metaphyseal and diaphyseal region with cortical thickening (Fig. 4).
3. Body PET-CT (to confirm the suspected disease): Perirenal and perivascular hypermetabolic foci associated with a perirenal rind of soft-tissue and perivascular soft-tissue (Fig. 5).
Due to these findings, a biopsy of the dural mass was performed.
Discussion
A. BACKGROUND [1, 4]
Myeloid stem cells differentiate into erythrocytes, eosinophils, basophils, mast cells, megakaryocytes, neutrophils, and monocytes. Monocytes further differentiate into macrophages and dendritic cells. Histiocytic disorders are a group of diseases derived from macrophages and dendritic cells.
The WHO's classification arranges histiocytic disorders into three groups: dendritic cell disorders, macrophage-related disorders, and malignant histiocytic disorders.
- Dendritic cell disorder: Langerhans cell histiocytosis is the most common. Less common Erdheim-Chester disease (ECD) and juvenile xanthogranuloma.
- Macrophage-related disorders include Rosai-Dorfman disease and haemophagocytic lymphohistiocytosis.
-Malignant histiocytic disorders: Leukaemias and malignant tumours.
Therefore, non-Langerhans cell histiocytoses include Rosai-Dorfman disease, ECD, Haemophagocytic lymphohistiocytosis and Juvenile xanthogranuloma. ECD is a rare form of non-Langerhans' cell histiocytosis. Individuals affected by this disease are typically adults (5th and 7th decade).
B. CLINICAL PERSPECTIVE [2]
The most common presenting symptom of ECD is bone pain. If there is CNS involvement, diabetes insipidus is the most common manifestation (as in LCH).
C. IMAGING PERSPECTIVE [1, 2, 3]
- Typical MRI findings - Brain:
1. Hypothalamic-Pituitary Involvement: Loss of posterior pituitary "bright spot" or thickened mass-like lesion in stalk/hypothalamus with homogeneous intense enhancement.
2. Meningeal Lesions: Meningioma-like mass lesions, single or multiple dural masses, or diffuse pachymeningeal thickening. These lesions tend to be hypointense on T2, and isointense on T1, with homogeneous intense enhancement.
3. Parenchymal lesions: Multiple enhancing parenchymal focal nodules or masses, supratentorial or infratentorial affecting predominantly cerebral hemispheres, hypothalamus, and brainstem. These lesions typically are isointense on T1, an iso/hypointense on T2, showing intense homogeneous enhancement. Bilateral symmetric high signal intensity in the dentate nucleus areas on T2 seems to be associated to cerebellar ataxia.
4. Vascular Involvement: Intracranial periarterial enhancing masses, stenotic circumferential lesions.
5. Orbital Involvement: Bilateral intraconal masses, hypointense on both T1 and T2 and with intense enhancement.
6. Sinus and Skull Involvement: Facial or skull bone thickening, maxillary, sphenoid sinus wall or ethmoidal cell wall osteosclerosis.
- Typical PET-CT findings (brain and whole body): Increased 18F-FDG uptake can be found in long bones and in extra-skeletal locations: pituitary, peri-orbital, mesenteric, skin/breast nodes, periaortic, perineural, muscular, or pericardial thickening.
- Plain films (brain and whole body): Cortical thickening of the bones with sclerotic coarsened trabeculae and epiphyseal sparing.
- Biopsy: Cellular proliferation composed by large cells (hystiocitic) which were CD1a (-), S100 (-) but CD68 (+) and Factor XIII (+). These findings are consistent with Erdheim-Chester Disease.
D. OUTCOME
Treatment includes close observation, interferon therapy, or chemotherapy. Pulmonary fibrosis and cardiac failure are the most common causes of death. This patient was treated with PEG-interferon with a mild improvement of his disease.
Differential Diagnosis List
Erdheim Chester disease - CNS involvement
Meningioma
Lymphoma
Metastases
Sarcoid
IgG4-Related Intracranial Hypertrophic Pachymeningitis
Final Diagnosis
Erdheim Chester disease - CNS involvement
