La maladie de Rosai-Dorfman-Destombes est une histiocytose inflammatoire polymorphe : étude phénotypique multicentrique de 47 patients

Histiocytic disorders

The historic term 'histiocytosis' meaning 'tissue cell' is used as a unifying concept for diseases characterized by pathogenic myeloid cells that share histological features with macrophages or dendritic cells. These cells may arise from the embryonic yolk sac, fetal liver or postnatal bone marrow. Prior classification schemes align disease designation with terminal phenotype: for example, Langerhans cell histiocytosis (LCH) shares CD207+ antigen with physiological epidermal Langerhans cells. LCH, Erdheim-Chester disease (ECD), juvenile xanthogranuloma (JXG) and Rosai-Dorfman disease (RDD) are all characterized by pathological ERK activation driven by activating somatic mutations in MAPK pathway genes. The title of this Primer (Histiocytic disorders) was chosen to differentiate the above diseases from Langerhans cell sarcoma and malignant histiocytosis, which are hyperproliferative lesions typical of cancer. By comparison LCH, ECD, RDD and JXG share some features of malignant cells including activating MAPK pathway mutations, but are not hyperproliferative. 'Inflammatory myeloproliferative neoplasm' may be a more precise nomenclature. By contrast, haemophagocytic lymphohistiocytosis is associated with macrophage activation and extreme inflammation, and represents a syndrome of immune dysregulation. These diseases affect children and adults in varying proportions depending on which of the entities is involved.

Rosai-Dorfman disease: an overview

CONTEXT

Rosai-Dorfman disease is an uncommon histiocytic disorder most frequently presenting as bilateral cervical lymphadenopathy in children and young adults. Extranodal disease occurs in a significant proportion of patients. It has been recently classified as part of the 'R group' of histiocytoses by the Histiocyte Society in 2016. Cutaneous Rosai-Dorfman disease is regarded as a separate disease entity that falls into the 'C group' of histiocytoses according to this classification system. The pathogenesis was previously poorly understood; however, recent evidence demonstrating clonality in a subset of cases raises the possibility of a neoplastic process. A possible association with IgG4-related disease remains controversial.

OBJECTIVES

To provide a comprehensive review of Rosai-Dorfman disease, including nodal, extranodal and cutaneous forms, with a particular emphasis on new insights into the possible clonal nature of the disease; to discuss the recently revised classification of the histiocytoses by the Histiocyte Society; and to summarise the findings from the literature regarding the controversial association with IgG4-related disease.

DATA SOURCES

This review is based on published peer-reviewed English literature.

CONCLUSIONS

Classic Rosai-Dorfman disease, which may be sporadic or familial, is considered a separate entity from cutaneous disease, which is reflected in the revised classification of histiocytoses. An increase in IgG4-positive plasma cells may be seen in Rosai-Dorfman disease. This finding in isolation is of limited significance and should be interpreted with caution. Studies investigating the molecular profile of the disease show that in at least a subset of cases the disease is a clonal process. The classification of Rosai-Dorfman disease is therefore likely to change as our understanding of the aetiopathogenesis evolves.

Fine-needle aspiration specimens of 3 cases of intra-abdominal Rosai-Dorfman disease with comprehensive review of the literature

INTRODUCTION

Rosai-Dorfman disease (RDD) is a rare usually self-limited non-Langerhans cell histiocytosis of unknown etiology. Nodal and extranodal RDD appear to represent distinct conditions with different molecular alterations and prognosis. They also pose different diagnostic challenges on biopsies and fine-needle aspiration (FNA) cytology. The aim of this study was to report on 3 cases of intra-abdominal RDD and perform an extensive review of the literature on FNA findings of RDD.

MATERIALS AND METHODS

We reviewed FNA specimens from cases diagnosed histologically or cytologically as RDD during the past 10 years. We searched the PubMed and Google Scholar databases for cases of RDD sampled by FNA.

RESULTS

We identified 3 cases of intra-abdominal RDD, involving the kidney, periportal lymph node, and pancreas. FNA of the latter was hypocellular with fibrosis and was nondiagnostic. FNA of the first 2 yielded hypercellular smears that were diagnosed as RDD due to the identification of emperipolesis occurring in large uni- or binucleated histiocytes with large nuclei, fine chromatin, and prominent nucleoli in smears and cell-block sections. Immunohistochemistry showed positive staining for S100 and CD68 and negative staining for CD1a. The large histiocytes with emperipolesis were more difficult to identify histologically and their demonstration required immunohistochemical stains.

CONCLUSION

Our experience and an extensive review of the literature suggest that extranodal RDD can be diagnosed on FNA, and that the recognition of histiocytes with emperipolesis may be less challenging cytologically than histologically. The fibrosis frequently seen in extranodal RDD may lead to nondiagnostic aspirates, however.

Imaging of Histiocytosis in the Era of Genomic Medicine

Histiocytosis describes a group of diseases that have long been considered enigmatic in the history of medicine. Recently, novel genomic analyses have identified somatic oncogenic driver mutations responsible for the pathogenesis of these entities. These discoveries have led to the recharacterization of histiocytoses as neoplastic diseases and have opened a new era of precision medicine approaches for treatment. The histiocytic disorders demonstrate a variety of imaging manifestations involving multiple organ systems, and radiologists play a major role in diagnosis and monitoring. An up-to-date knowledge of the novel genomic discoveries and their implications is essential for radiologists to understand the new approaches to treating histiocytic disorders and to contribute as key members of the multidisciplinary treatment team. This article provides a cutting-edge review of the novel concepts in histiocytosis, with a focus on recent genomic discoveries and precision medicine approaches to treating the disease, and describes imaging manifestations with correlative histologic and genomic findings, with an emphasis on adult-onset cases and uncommon subtypes. ^©RSNA, 2018.

Histiocytoses: emerging neoplasia behind inflammation

Histiocytoses are disorders characterised by inflammation and the accumulation of cells derived from the monocyte and macrophage lineages, which results in tissue damage. Although they are often considered rare disorders with protean clinical manifestations, considerable advances in the understanding of their genetics have led to increased clinical recognition of these conditions, and fuelled further insights into their pathogenesis. In this Review, we describe insights into the cells of origin, molecular pathology, clinical features, and treatment strategies for some of the most common histiocytic disorders, including Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease. With the discovery of recurrent mutations affecting the mitogen-activated protein kinase and mTOR-AKT pathways in some of these histiocytoses, our understanding of these diseases has now evolved from the concept of a primary inflammatory condition to that of a clonal neoplastic disease. This understanding has led to the development of effective mechanism-based therapeutic strategies for patients with histiocytic diseases.

Uncommon histiocytic disorders: Rosai–Dorfman, juvenile xanthogranuloma, and Erdheim–Chester disease

Rosai–Dorfman disease (RDD), juvenile xanthogranuloma (JXG), and Erdheim–Chester disease (ECD) are non-Langerhans cell (non-LCH) disorders arising from either a dendritic or a macrophage cell. RDD is a benign disorder that presents with massive lymphadenopathy, but can have extranodal involvement. In most cases, RDD is self-limited and observation is the standard approach. Treatment is restricted to patients with life-threatening, multiple-relapsing, or autoimmune-associated disease. JXG is a pediatric histiocytosis characterized by xanthomatous skin lesions that usually resolve spontaneously. In a minority of cases, systemic disease can occur and can be life threatening. Juvenile myelomonocytic leukemia (JMML), as well as germline mutations in NF1 and NF2, have been reported in children with JXG. Recent whole-exome sequencing of JXG cases did not show the BRAF-V600E mutation, although 1 patient had PI3KCD mutation. ECD is an adult histiocytosis characterized by symmetrical long bone involvement, cardiovascular infiltration, a hairy kidney, and retroperitoneal fibrosis. Central nervous system involvement is a poor prognostic factor. Interferon-α is the standard as front-line therapy, although cladribine and anakinra can be effective in a few refractory cases. More than one-half of ECD patients carry the BRAF-V600E mutation. Currently, >40 patients worldwide with multisystemic, refractory BRAF-V600E+ ECD have been treated with vemurafenib, a BRAF inhibitor, which was found to be highly effective. Other recurrent mutations of the MAP kinase and PI3K pathways have been described in ECD. These discoveries may redefine ECD, JXG, and LCH as inflammatory myeloid neoplasms, which may lead to new targeted therapies.

Uncommon histiocytic disorders: Rosai-Dorfman, juvenile xanthogranuloma, and Erdheim-Chester disease

Rosai-Dorfman disease (RDD), juvenile xanthogranuloma (JXG), and Erdheim-Chester disease (ECD) are non-Langerhans cell (non-LCH) disorders arising from either a dendritic or a macrophage cell. RDD is a benign disorder that presents with massive lymphadenopathy, but can have extranodal involvement. In most cases, RDD is self-limited and observation is the standard approach. Treatment is restricted to patients with life-threatening, multiple-relapsing, or autoimmune-associated disease. JXG is a pediatric histiocytosis characterized by xanthomatous skin lesions that usually resolve spontaneously. In a minority of cases, systemic disease can occur and can be life threatening. Juvenile myelomonocytic leukemia (JMML), as well as germline mutations in NF1 and NF2, have been reported in children with JXG. Recent whole-exome sequencing of JXG cases did not show the BRAF-V600E mutation, although 1 patient had PI3KCD mutation. ECD is an adult histiocytosis characterized by symmetrical long bone involvement, cardiovascular infiltration, a hairy kidney, and retroperitoneal fibrosis. Central nervous system involvement is a poor prognostic factor. Interferon-α is the standard as front-line therapy, although cladribine and anakinra can be effective in a few refractory cases. More than one-half of ECD patients carry the BRAF-V600E mutation. Currently, >40 patients worldwide with multisystemic, refractory BRAF-V600E(+) ECD have been treated with vemurafenib, a BRAF inhibitor, which was found to be highly effective. Other recurrent mutations of the MAP kinase and PI3K pathways have been described in ECD. These discoveries may redefine ECD, JXG, and LCH as inflammatory myeloid neoplasms, which may lead to new targeted therapies.