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

68Ga-FAPI and 18F-FDG PET/CT Imaging in Langerhans Cell Histiocytosis for Recurrence and Therapeutic Response Assessment

ABSTRACT

A 2-and-a-half-year-old boy with a previous history of Langerhans cell histiocytosis reached remission as assessed by 18F-FDG PET/CT. Routine follow-up 18F-FDG PET/CT revealed the appearance of new bone lesions in the right scapula and right ischium with abnormal FDG activity 3 months after the end of treatment, and Langerhans cell histiocytosis recurrence was considered. Meanwhile, these lesions also showed increased FAPI uptake. After adjusting the chemotherapy regimen, both FDG and FAPI uptake almost disappeared in these lesions.

Imaging in Erdheim-Chester Disease

Erdheim-Chester disease (ECD) is a rare, multisystemic, inflammatory, non-Langerhans cell histiocytic neoplasm. The discovery of recurrent and somatic mutations in the mitogen-activated protein kinase signaling pathway, most commonly BRAFV600E, has led to a reclassification of ECD from an inflammatory disorder to a neoplastic process. It is now included in the revised 2016 World Health Organization classification of hematopoietic tumors and in the Langerhans group in the revised 2016 Histiocytosis Classification of the Histiocyte Society. When symptomatic, ECD most commonly manifests with bone pain and fatigue. Also, neurologic manifestations, central diabetes insipidus, exophthalmos, and periorbital xanthelasma-like lesions are frequently encountered. Pathologic findings may vary depending on the site of biopsy and may display a spectrum of features. Thus, due to the diverse clinical presentation and variable histologic findings, imaging can often show the first sign of the disease. Radiologic findings are, however, interpreted in conjunction with clinical and histologic findings to establish the diagnosis of ECD. From providing classic findings that facilitate diagnosis to helping radiologists determine the extent of disease and predicting a prognosis, the role of radiology in ECD has evolved with the understanding of the disease itself. Insights into the molecular pathogenesis and the development of targeted therapeutic agents along with approval of vemurafenib and cobimetinib have necessitated revision of the guidelines for the management of ECD. The authors discuss various radiologic findings of ECD and differential diagnoses by using an organ system-based approach and briefly describe the revised consensus recommendations for evaluation, diagnosis, and treatment based on the International Medical Symposia on ECD from a radiologist's perspective. ©RSNA, 2024 Supplemental material is available for this article. The full digital presentation is available online.

Predominantly multiple focal non-cystic renal lesions: an imaging approach

Multiple non-cystic renal lesions are occasionally discovered during imaging for various reasons and poses a diagnostic challenge to the practicing radiologist. These lesions may appear as a primary or dominant imaging finding or may be an additional abnormality in the setting of multiorgan involvement. Awareness of the imaging appearance of the various entities presenting as renal lesions integrated with associated extrarenal imaging findings along with clinical information is crucial for a proper diagnostic approach and patient work-up. This review summarizes the most relevant causes of infectious, inflammatory, vascular, and neoplastic disorders presenting as predominantly multiple focal non-cystic lesions.

Dural involvement in central nervous system langerhans cells histiocytosis (LCH) on FDG PET/CT: Case report and review of CNS manifestations of LCH on PET/CT

We report a case of multisystem Langerhans cell histiocytosis in a pediatric patient with central nervous system involvement, highlighting F-18(FDG) uptake characteristics of dural sites of disease. We also highlight the advantages of functional data offered by FDG-PET as a useful follow-up tool to assess viability and, therefore, treatment response of previously known central nervous system lesions. The utility of recognizing characteristic patterns of FDG uptake in dural disease is also applicable in cases of diagnostic uncertainty, such as when evaluating isolated dural lesions or when distinguishing between Langerhans cell histiocytosis and similar appearing lesions such as meningiomas.

FDG PET/CT Imaging of Liver and Spleen Histiocytic Sarcoma

ABSTRACT

Histiocytic sarcoma is a tumor of the lymphohematopoietic system characterized by macrophage morphology and immunophenotype. Here, we report FDG PET/CT images of a 50-year-old man with coexisting histiocytic sarcoma of the liver and spleen. Images showed multiple enhanced uptake lesions of FDG in both the liver and spleen. Ultimately, histiocytic sarcoma was confirmed by the biopsy histopathology.

Identification and characterization of stromal-like cells with CD207+/low CD1a+/low phenotype derived from histiocytic lesions - a perspective in vitro model for drug testing

BACKGROUND

Histiocytoses are rare disorders manifested by increased proliferation of pathogenic myeloid cells sharing histological features with macrophages or dendritic cells and accumulating in various organs, i.a., bone and skin. Pre-clinical in vitro models that could be used to determine molecular pathways of the disease are limited, hence research on histiocytoses is challenging. The current study compares cytophysiological features of progenitor, stromal-like cells derived from histiocytic lesions (sl-pHCs) of three pediatric patients with different histiocytoses types and outcomes. The characterized cells may find potential applications in drug testing.

METHODS

Molecular phenotype of the cells, i.e. expression of CD1a and CD207 (langerin), was determined using flow cytometry. Cytogenetic analysis included GTG-banded metaphases and microarray (aCGH) evaluation. Furthermore, the morphology and ultrastructure of cells were evaluated using a confocal and scanning electron microscope. The microphotographs from the confocal imaging were used to reconstruct the mitochondrial network and its morphology. Basic cytophysiological parameters, such as viability, mitochondrial activity, and proliferation, were analyzed using multiple cellular assays, including Annexin V/7-AAD staining, mitopotential analysis, BrdU test, clonogenicity analysis, and distribution of cells within the cell cycle. Biomarkers potentially associated with histiocytoses progression were determined using RT-qPCR at mRNA, miRNA and lncRNA levels. Intracellular accumulation of histiocytosis-specific proteins was detected with Western blot. Cytotoxicyty and IC50 of vemurafenib and trametinib were determined with MTS assay.

RESULTS

Obtained cellular models, i.e. RAB-1, HAN-1, and CHR-1, are heterogenic in terms of molecular phenotype and morphology. The cells express CD1a/CD207 markers characteristic for dendritic cells, but also show intracellular accumulation of markers characteristic for cells of mesenchymal origin, i.e. vimentin (VIM) and osteopontin (OPN). In subsequent cultures, cells remain viable and metabolically active, and the mitochondrial network is well developed, with some distinctive morphotypes noted in each cell line. Cell-specific transcriptome profile was noted, providing information on potential new biomarkers (non-coding RNAs) with diagnostic and prognostic features. The cells showed different sensitivity to vemurafenib and trametinib.

CONCLUSION

Obtained and characterized cellular models of stromal-like cells derived from histiocytic lesions can be used for studies on histiocytosis biology and drug testing.

Utility of 18F-FDG PET/CT in Assessment of Disease Extent and Response to Treatment in Xanthoma Disseminatum

The clinical utility of 18F-FDG PET/CT is being increasingly recognized in histiocytic disorders. We report the case of a 23-y-old woman who presented with slowly progressive, yellowish-brown papules, plaques, and nodules over her face and flexures. Besides the multiple cutaneous lesions, lesions of the brain, stomach, gallbladder, and marrow were additionally revealed by baseline 18F-FDG PET/CT. Skin biopsy and the overall clinical picture were consistent with xanthoma disseminatum. Subsequent PET/CT after cladribine therapy revealed a decrease in the extent and metabolic activity of most lesions, suggestive of a favorable response. This case report highlights the potential role of 18F-FDG PET/CT in the accurate assessment of disease extent and posttreatment response in rare histiocytic disorders.

Granulomatous annular diseases

Granulomatous skin disorders comprise a large group of diseases that are typically characterized by granuloma formation both in the skin and in many other tissues. Cutaneous lesions are usually seen as erythematous papules and plaques that may occasionally be arranged in an annular, ringlike configuration. The etiopathogenesis is unclear in most cases, and granuloma formation may be associated with various systemic, infectious, and metabolic disorders, foreign bodies, environmental antigens, or malignancies. Treatment options are dependent on the etiology, extent, and severity of the lesions. This review includes the clinical, histopathologic, and dermatoscopy findings, differentials, and treatment options for noninfectious granulomatous annular skin disorders.

FDG PET/CT in Mixed Langerhans Cell Histiocytosis and Erdheim-Chester Disease

ABSTRACT

The histiocytoses arise from hematopoietic bone marrow stem cells or monocytes. They range from limited to disseminated disease. We report a 31-year-old woman with multisystem Langerhans cell histiocytosis (LCH). The recognition that pericardial disease was rare in LCH prompted review of the initial limited biopsies, which helped establish a second diagnosis of Erdheim-Chester disease. The increasing recognition of mixed histiocytoses requires searching for Erdheim-Chester disease when a patient is diagnosed with LCH and vice versa. FDG PET/CT can help establish the diagnosis or suggest mixed disease based on the organs involved.

Langerhans Cell Histiocytosis Involving the Thymus and Heart With Simultaneous Thymoma: A Case Report

Langerhans cell histiocytosis (LCH) is a rare disease characterized by clonal expansion of CD1a+/CD207+ cells in lesions. The most frequent sites involved are bone and, less commonly, lymph nodes, lungs, and skin. The thymus or heart is rarely involved with LCH. In this case, we present a 73-year-old woman with a mediastinal mass. Histopathology after thymectomy identified this mass as type AB thymoma; notably, subsequent immunohistochemical tests showed lesions of LCH scattered in the region of thymoma. 18-Fluorodeoxyglucose PET/CT (18-FDG-PET/CT) was performed to make an overall assessment of the extent of this disease, which demonstrated suspicious cardiac involvement of LCH. This report highlights the importance of differentiating abnormalities of the thymus or mediastinal mass from LCH and the necessity of comprehensive evaluation for patients with LCH.

Rosai-Dorfman disease with spine involvement: A case report

RATIONALE

Rosai-Dorfman disease (RDD) is a rare, benign, self-limiting disease, also known as sinus histiocytosis with giant lymphadenopathy. Skeletal involvement is rare, and this isolated bone lesion usually occurs in adults with no other symptoms. It is estimated that 0.6% to 1% of RDD cases have isolated or complicated spinal lesions, which may occur in the bone, dura, and spinal parenchyma, but spinal RDD has no pathologic clinical or imaging features.

PATIENT CONCERNS

A 25-year-old woman presented with complaints of low back pain without obvious causes for a month.

DIAGNOSIS

RDD with spinal involvement.

INTERVENTIONS

Resection of the spinous process of the third lumbar spine was performed under epidural anesthesia.

OUTCOMES

At the time of discharge, the patient had no problems with autonomous activities and reported no discomfort. We also followed up the patient at 12 and 36 months after surgery, and the patient reported no discomfort, inconvenience, and no recurrence of symptoms. Imaging examination 1 year after surgery showed no recurrence.

LESSON

This case suggests that surgery for RDD with spinal involvement may not require internal fixation.

Langerhans cell histiocytosis presenting as an isolated brain tumour: A case report

BACKGROUND

Langerhans cell histiocytosis (LCH) is a rare proliferative histiocyte disorder. It can affect any organ or system, especially the bone, skin, lung, and central nervous system (CNS). In the CNS, the hypothalamic-pituitary is predominantly affected, whereas the brain parenchyma is rarely affected. LCH occurring in the brain parenchyma can be easily confused with glioblastoma or brain metastases. Thus, multimodal imaging is useful for the differential diagnosis of these intracerebral lesions and detection of lesions in the other organs.

CASE SUMMARY

A 47-year-old man presented with a headache for one week and sudden syncope. Brain computed tomography (CT) and magnetic resonance imaging showed an irregularly shaped nodule with heterogeneous enhancement. On ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/CT, a nodule with ¹⁸F-FDG uptake and multiple cysts in the upper lobes of both lungs were noted, which was also confirmed by high-resolution CT. Thus, the patient underwent surgical resection of the brain lesion for further examination. Postoperative pathology confirmed LCH. The patient received chemotherapy after surgery. No recurrence was observed in the brain at the 12-mo follow-up.

CONCLUSION

Multimodal imaging is useful for evaluating the systemic condition of LCH, developing treatment plans, and designing post-treatment strategies.

Mimics of Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare histiocytic neoplasm with frequent multiorgan involvement. An accurate diagnosis of ECD requires the correlation of clinical features, histopathologic and radiologic findings. We describe a case series of patients with a referral diagnosis of ECD, whereby the diagnosis was changed to non-histiocytic diseases after comprehensive review at a tertiary care center. This accurate revision of the referral diagnosis of ECD enabled initiation of proper disease-directed therapy in a timely manner for these patients and avoided unnecessary exposure to systemic cytotoxic chemotherapy or targeted agents. Our study highlights the value of a multidisciplinary team of histiocytosis experts in confirming the diagnosis of ECD and also brings attention to other conditions to consider that can mimic ECD, including osteopoikilosis, tenosynovial giant cell tumour, IgG4-related disease, fibrous dysplasia and chronic recurrent multifocal osteomyelitis.