18F-fluoride PET/CT aspect of an unusual case of Erdheim-Chester disease with histologic features of Langerhans cell histiocytosis

Histiocytosis and the nervous system: from diagnosis to targeted therapies

Histiocytoses are heterogeneous hematopoietic diseases characterized by the accumulation of CD68(+) cells with various admixed inflammatory infiltrates. The identification of the pivotal role of the mitogen-activated protein kinase (MAPK) pathway has opened new avenues of research and therapeutic approaches. We review the neurologic manifestations of 3 histiocytic disorders with frequent involvement of the brain and spine: Langerhans cell histiocytosis (LCH), Erdheim-Chester disease (ECD), and Rosai-Dorfman-Destombes disease (RDD). Central nervous system (CNS) manifestations occur in 10%-25% of LCH cases, with both tumorous or neurodegenerative forms. These subtypes differ by clinical and radiological presentation, pathogenesis, and prognosis. Tumorous or degenerative neurologic involvement occurs in 30%-40% of ECD patients and affects the hypothalamic-pituitary axis, meninges, and brain parenchyma. RDD lesions are typically tumorous with meningeal or parenchymal masses with strong contrast enhancement. Unlike LCH and ECD, neurodegenerative lesions or syndromes have not been described with RDD. Familiarity with principles of evaluation and treatment both shared among and distinct to each of these 3 diseases is critical for effective management. Refractory or disabling neurohistiocytic involvement should prompt the consideration for use of targeted kinase inhibitor therapies.

Central Nervous System Complications of Erdheim-Chester Disease: FDG PET/CT Findings

ABSTRACT

Erdheim-Chester disease is an uncommon non-Langerhans cell histiocytosis. The diagnosis depends on imaging and histological criteria. The most common presentation is the multiple bone lesions with involvement of at least 1 more organ. We present the FDG PET/CT findings of a 19-year-old man who presented with central nervous system symptoms such as progressive polyuria, polydipsia, gait disturbances, and eye pain and was later diagnosed with Erdheim-Chester disease.

Histiocytosis and Neoplasms of Macrophage-Dendritic Cell Lineages: Multimodality Imaging with Emphasis on PET/CT

Histiocytosis is a rare inflammatory process characterized by pathologic infiltration and accumulation of cells derived from the monocytic lineage in normal tissue. It encompasses more than 100 different subtypes of disorders that were recently classified into five main groups: (a) Langerhans-related histiocytosis, (b) Rosai-Dorfman histiocytosis, (c) cutaneous and mucocutaneous histiocytosis, (d) malignant histiocytosis, and (e) hemophagocytic lymphohistiocytosis and macrophage activation syndrome. Langerhans cell histiocytosis is the most common histiocytic disorder. Less common types include Erdheim-Chester disease, Rosai-Dorfman disease, adult and juvenile xanthogranuloma, necrobiotic xanthogranuloma, histiocytic sarcoma, interdigitating dendritic cell sarcoma, Langerhans cell sarcoma, and hemophagocytic lymphohistiocytosis. Although the pathogenesis of these disorders may be attributable to mutations in the oncogenic driver, recent discoveries have shown that inflammation and fibrosis secondary to mutated histiocytes, rather than a proliferative cell mechanism, result in manifestation of the disease. Diagnosis, which relies on a multidisciplinary approach, is challenging and often delayed because clinical findings are nonspecific and may mimic malignant processes at radiologic evaluation. Compared with conventional imaging, PET/CT allows detection of the increased metabolic activity in histiocytes. Diagnostic algorithms for histiocytic disorders should include functional imaging with fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) PET/CT, which provides a comprehensive whole-body evaluation of their potential involvement with multiple organ systems and allows monitoring of therapeutic response. The most recent revised classification, pathophysiologic and clinical manifestations, sites of involvement, and imaging features of histiocytosis are described in this review and a multimodality approach is used, with emphasis on ¹⁸F-FDG PET/CT evaluation. ^©RSNA, 2021.

Novel Musculoskeletal and Orthopedic Applications of 18F-Sodium Fluoride PET

PET imaging with ¹⁸F-sodium fluoride (NaF), combined with computed tomography or magnetic resonance, is a sensitive method of assessing bone turnover. Although NaF-PET is gaining popularity in detecting prostate cancer metastases to bone marrow, osseous changes represent secondary effects of cancer cell growth. PET tracers more appropriate for assessing prostate cancer metastases directly portray malignant activity and include ¹⁸F-fluciclovine and prostatic specific membrane antigen ligands. Recent studies investigating NaF-PET suggest utility in the assessment of benign musculoskeletal disorders. Emerging applications in assessing traumatic injuries, joint disease, back pain, orthopedic complications, and metabolic bone disease are discussed.

The triptych of mixed histiocytosis: a systematic review of 105 cases and proposed clinical classification

Histiocytoses are one of the ultimate diagnostic challenges that every physician face at least once in his/her life. Giving their protean manifestation and differentiated therapeutic needs, histiocytosis requires extensive characterization and multidisciplinary management. Mixed histiocytosis is an emerging group of syndromes defined by the overlap of Langerhans cell histiocytosis and another histiocytic disorder of different type. Despite rare, it may account for up to a fifth of systemic histiocytosis patients in some series. In this work, we comprehensively review for the first time the clinical, radiological, histopathological and molecular features of mixed histiocytosis in children and adults. Moreover, we propose a clinical classification in three groups that differentiate patients with systemic involvement and worse overall survival to other groups with more localized manifestations and indolent behavior, wanting to ease their recognition and treatment. Interestingly we also found that mixed histiocytosis harbor BRAFV600E mutations with a higher frequency comparing to all other histiocytoses, and may therefore benefit of specific inhibitory drugs.

Erdheim-Chester Disease: A Case Report and Review of the Literature

Erdheim-Chester disease (ECD) is a rare form of non-Langerhans’ cell histiocytosis characterized by xanthogranulomatous infiltration of foamy histiocytes surrounded by fibrosis. ECD may be asymptomatic or present as a multi-systemic disease with life-threatening manifestations, most commonly involving the skeletal system. Immunohistochemical staining demonstrates cells that are CD68+, CD1a–, and S100– with an absence of Birbeck granules. We report a case of a 69-year old male patient who presented with neurological symptoms – eventually thought to be separate to his diagnosis of ECD. It represents the ability to diagnose ECD based just on radiological findings in an otherwise asymptomatic individual.

Clinical Nononcologic Applications of PET/CT and PET/MRI in Musculoskeletal, Orthopedic, and Rheumatologic Imaging

OBJECTIVE

With improvements in PET/CT and PET/MRI over the last decade, as well as increased understanding of the pathophysiology of musculoskeletal diseases, there is an emerging potential for PET as a primary or complementary modality in the management of rheumatologic and orthopedic conditions.

CONCLUSION

We discuss the role of PET/CT and PET/MRI in nononcologic musculoskeletal disorders, including inflammatory and infectious conditions and postoperative complications. There is great potential for an increased role for PET to serve as a primary or complementary modality in the management of orthopedic and rheumatologic disorders.

Complete remission of critical neurohistiocytosis by vemurafenib

Objective:

To describe a patient with life-threatening brainstem neurohistiocytosis who recovered completely upon targeted treatment with the V600E mutation-specific BRAF inhibitor vemurafenib.

Methods:

We report clinical, histiologic, genetic, and sequential imaging findings, including fluorodeoxyglucose (FDG)-PET, over a follow-up period of 11 months.

Results:

The patient presented with central hyperventilation, skeletal and perirenal Erdheim-Chester disease, and cutaneous Langerhans cell histiocytosis. A BRAF V600E hotspot mutation was detected in all afflicted tissues. Therapy with vemurafenib led to complete and stable clinical remission of CNS lesions and systemic disease that could be demonstrated by brain MRI and whole-body FDG-PET.

Conclusions:

Neurologic involvement in Erdheim-Chester disease usually confers a poor prognosis. In this patient, vemurafenib was well-tolerated and highly efficacious for severe brainstem involvement in Erdheim-Chester disease with overlapping Langerhans cell histiocytosis. This case illustrates the heterogeneous phenotypic spectrum of neurohistiocytosis and underscores the importance of genetic testing.

Classification of evidence:

This article provides Class IV evidence. This is a single observational study without controls.

Visualization of orbital involvement of Erdheim-Chester disease on PET/CT

We report a 58-year-old man who presented with swelling and redness in his left eye, headache, and blurred vision. A contrast-enhanced CT of the orbits revealed bilateral orbital masses. Whole-body PET/CT showed bilateral retrobulbar hypermetabolic soft tissue lesions, multiple areas of soft tissue involvement, and osseous lesions in bilateral lower extremities. An open surgical biopsy of the left orbital mass revealed xanthomatous non-Langerhans histiocytic infiltrate with Touton giant cells, positive for CD68 but negative for CD1a, establishing a diagnosis of Erdheim-Chester disease.

Consensus guidelines for the diagnosis and clinical management of Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare, non-Langerhans histiocytosis. Recent findings suggest that ECD is a clonal disorder, marked by recurrent BRAFV600E mutations in >50% of patients, in which chronic uncontrolled inflammation is an important mediator of disease pathogenesis. Although ∼500 to 550 cases have been described in the literature to date, increased physician awareness has driven a dramatic increase in ECD diagnoses over the last decade. ECD frequently involves multiple organ systems and has historically lacked effective therapies. Given the protean clinical manifestations and the lack of a consensus-derived approach for the management of ECD, we provide here the first multidisciplinary consensus guidelines for the clinical management of ECD. These recommendations were outlined at the First International Medical Symposium for ECD, comprised of a comprehensive group of international academicians with expertise in the pathophysiology and therapy of ECD. Detailed recommendations on the initial clinical, laboratory, and radiographic assessment of ECD patients are presented in addition to treatment recommendations based on critical appraisal of the literature and clinical experience. These formalized consensus descriptions will hopefully facilitate ongoing and future research efforts in this disorder.

Pineal gland involvement in Erdheim-Chester disease detected on (18)F-FDG PET-CT imaging: a case report and review of literature

Erdheim-Chester disease (ECD) is a rare non-Langerhan's cell histiocytosis affecting multiple organ systems. The most common systemic manifestations are bone lesions, infiltration of the pituitary stalk sometimes leading to diabetes insipidus, pulmonary fibrosis, cardiac failure and exophthalmus. Neurological symptoms as the first clinical manifestations of ECD have been reported in less than one third of cases. We report a rare presentation of a patient of ECD on 18F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography-computed tomography which revealed abnormal (18)F-FDG accumulation in the region of pineal gland, pericardium and bilateral distal tibiae.