Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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September 26, 2024
Langerhans Cell Histiocytosis
- Background:
- LCH is a rare lymphoproliferative disorder characterized by the proliferation of Langerin-positive (CD207+) cells derived from myeloid dendritic cells.
- It mainly affects children and young adults, and it affects men two times more than women.
- Clinical presentation:
- The skeleton is the most affected organ in LCH. Temporal bone involvement is common, and ~15–61% of patients experience ear involvement with symptoms such as hearing loss, otalgia, or external auditory canal masses and polyps. Other symptoms include systemic findings such as weight loss or fever, lymphadenopathy, skin rash, dyspnea or tachypnea, polydipsia/polyuria, bone pain, or gingival hypertrophy. The clinical presentation and extent of involvement are variable, as the disease may present as a single lesion, multiple lesions in a single organ, or early multisystem involvement. The prognosis also ranges from spontaneous regression to rapidly progressive organ failure.
- Key diagnostic features:
- There is no pathognomonic imaging feature of LCH. CT scans are often initially obtained to assess initial musculoskeletal and respiratory symptoms. MRI may be obtained as an additional imaging modality to further characterize musculoskeletal tumors and soft tissue involvement. FDG-PET/CT may be obtained during the diagnostic assessment if a systemic disorder is suspected, as well as to possibly guide the selection of a biopsy site because the diagnosis cannot be made on imaging alone. The characteristic imaging appearance of skeletal LCH is an expansile lytic lesion that unevenly erodes the inner and outer table of the skull, producing a “beveled-edge” appearance. The imaging in this case showed a well-defined lytic and destructive bone lesion with enhancing soft tissue involving the squamous and mastoid temporal bone.
- CT: Sharp lytic calvaria (most common bony site) or skull base defect with beveled edges, with an associated soft-tissue mass
- MR: Skull/calvarial lesions demonstrate mild T2 hyperintensity, with avid enhancement. Often demonstrate low ADC due to high cellular density, mimicking malignancy.
- Bone scan: Variable uptake
- PET: Increased FDG uptake in proliferating lesions; decreased uptake in burned out lesions
- Brain involvement: Pituitary/infundibulum - thickened pituitary stalk, absent posterior pituitary T1 bright neurohypophysis
- There is no pathognomonic imaging feature of LCH. CT scans are often initially obtained to assess initial musculoskeletal and respiratory symptoms. MRI may be obtained as an additional imaging modality to further characterize musculoskeletal tumors and soft tissue involvement. FDG-PET/CT may be obtained during the diagnostic assessment if a systemic disorder is suspected, as well as to possibly guide the selection of a biopsy site because the diagnosis cannot be made on imaging alone. The characteristic imaging appearance of skeletal LCH is an expansile lytic lesion that unevenly erodes the inner and outer table of the skull, producing a “beveled-edge” appearance. The imaging in this case showed a well-defined lytic and destructive bone lesion with enhancing soft tissue involving the squamous and mastoid temporal bone.
- Differential diagnosis:
- As no imaging feature is pathognomonic to LCH, a differential diagnosis and recommendations for biopsy should always be offered. The main differential diagnoses for a solitary aggressive temporal bone lesion in the presence of lymphadenopathy elsewhere include other lymphoproliferative disorders, such as leukemia and lymphoma, as well as other histiocytic disorders like Erdheim-Chester disease. However, these diagnoses were considered unlikely due to the patient's recent diagnosis of biopsy-proven LCH at an inguinal lymph node. Another possibility is a separate primary neoplasm like osteosarcoma, chondrosarcoma, Ewing sarcoma, squamous cell carcinoma, or plasmacytoma. Osteosarcoma and chondrosarcoma were deemed less likely due to the absence of matrix production, while Ewing sarcoma is extremely rare in the cranial region. Squamous cell carcinoma and plasmacytoma were also considered unlikely due to the patient's age, as they are uncommon in this age group. Aggressive infections like coalescent mastoiditis or necrotizing otitis externa were also considered but deemed less likely due to the lack of rapid progression of symptoms. Ultimately, the most likely diagnosis in this case is osseous LCH, given the presence of an expansile lytic lesion in a patient with known LCH elsewhere.
- Management/Treatment:
- Observation, chemoradiation, steroid, and surgery (curettage)
- Systemic chemotherapy is recommended for patients with multisystem LCH or CNS risk lesions. If active disease resolves after initial therapy, maintenance chemotherapy can be started for 12 months. Management of single-system LCH typically involves observation or local therapies, such as excision of unifocal lesions or limited single-system LCH. Systemic chemotherapy regimens can be considered for extensive, refractory, or progressive disease. Follow-up monitor should continue until pubertal development and/or at least 5 years after completing treatment. Generally, each case of LCH should have treatment individualized and optimized for the patient in question.
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