A meta-analysis of cases of Rosai Dorfman disease reported on the African continent and a description of two cases from a tertiary academic hospital in Johannesburg, South Africa.

Rosai-Dorfman-Destombes disease (RDD) is a rare non-Langerhans cell histiocytosis characterized by the accumulation of activated histiocytes within affected tissues. The original haematopathological description of RDD has links to the late South African born haematopathologist, Ronald Dorfman, with a descriptive account of two cases of the disease treated at Chris Hani Baragwanath Academic Hospital are described herein. Alongside the two case descriptions is a meta-analysis of 149 published cases from the African continent. Sequential literature searches were performed on Google Scholar and PubMed with the search terms "sinus histiocytosis with massive lymphadenopathy", "Rosai-Dorfman disease", "Rosai-Dorfman Destombes" and "lymphadenopathy" together with the name of each individual country on the African continent, from Algeria to Zimbabwe. All possible cases of RDD reported in published literature from Africa were captured on a Microsoft Excel spreadsheet recording details, where available, of demographics, nodal (nodal groups) or extra-nodal disease as well as treatment. Of the 54 African countries on the continent, published data was available from half of these countries (n=27). Nigeria (35), Tunisia (25) and South Africa (23) contributed the majority of cases for data collection with a clear paucity of reportable information available from Central Africa. Of the 149 cases from the African continent, the majority were from patients aged ten years and younger with a decrease in reported cases in patients with increasing age. The mean age at diagnosis was 25.66 years [95% CI: 21.81-29.51] with a median age of diagnosis of 24.5 years. The youngest patient in the series was 3 months old and the oldest patient aged 72 (range 71.75 years, IQR 31). The cases reported were fairly split between males and females with a male-to-female ratio of 1.07: 1. HIV seropositivity was reported in seven patients (4.8%) and no HIV results were available in 104 patients (71.2%). Disease presentation was split between nodal disease in 43% of patients (n=64), Extra nodal (EN) disease in 32.9% (n=32), mixed (nodal/EN) disease in 11.4% (n=17) and unknown in 12.8% (n=19). Fever was present in 18.1% (n=27) of cases. Hepatic enlargement was noted in nine patients (6%) and splenic enlargement in four patients (2.7%). Commonly ascribed sites of EN disease, in descending order, were skin and soft tissue, ocular, ear/nose/throat (ENT), abdominal organ(s), bone, lung/pleura, brain parenchyma (including dura), endocrine glands, spine, breast, pericardium, pseudotumour formation (unspecified site), joint(s), peripheral nerves and genitourinary tract disease. The upfront administration of glucocorticosteroids was seen in the majority of cases. Rosai-Dorfman-Destombes, although a rare disorder, should be considered as a differential diagnosis in patients with massive bilateral cervical lymphadenopathy and is confirmed with accompanying pathological changes on microscopic and immunohistochemical examination of biopsy specimens. The role of infection, particularly HIV infection, is considered to be a possible contributor to the pathogenesis of RDD and HIV testing in patients from areas of high HIV endemicity with co-existing RDD should be undertaken. Consideration for mycobacterium tuberculosis infection in patients with generalized significant lymphadenopathy still remains an important differential for massive lymphadenopathy and requires confirmation by appropriate microbiological investigations. The treatment landscape in RDD is limited in many resource-poor settings, with the upfront use of glucocorticosteroids employed routinely in the majority of cases.

Rosai-Dorfman-Destombes Disease in the Pediatric Head and Neck.

BACKGROUND: Rosai-Dorfman-Destombes disease (RDD), or sinus histiocytosis with massive lymphadenopathy, is a rare form of non-Langerhans cells histiocytosis. It has a wide-ranging variability in presentation since first described in 1969 but much of its characteristics in children remain unknown. METHODS: A retrospective chart review of children diagnosed with RDD at a tertiary care children's hospital was conducted from 2000 to 2021. RESULTS: Twelve RDD patients were identified, with an average age of 7 years (SD 4.3). Males comprised 58% of the cohort, and African American ethnicity was most common (42%). Nodal RDD was found in 7 patients (58%). Nine patients (75%) presented RDD within the head and neck, 6 of whom had nodal RDD. The most common presentation was cervical lymphadenopathy, which most often involved levels V (67%), II (56%), III (44%), and I (11%), in order of frequency. Recurrence and persistence of disease after initial treatment was common, with 5 (42%) being disease free at the time of the last follow up. Fifty-eight percent (7/12) developed recurrence or had persistent disease and 4 required adjuvant systemic treatment with corticosteroids and/or chemotherapy. One patient succumbed after developing treatment related acute myelodysplastic leukemia (t-AML) from chemotherapy used to treat recurrent RDD. CONCLUSION: Pediatric RDD presents at a young age and most commonly involving cervical lymphadenopathy. Ongoing surveillance in the setting of persistence or recurrence without clearly defined prognostic risk factors is important.

Rosai-Dorfman disease: A pathological experience from 2 tertiary care hospitals in Western Saudi Arabia.

OBJECTIVES: To document the clinicopathological features of Rosai-Dorfman disease (RDD) at 2 tertiary hospitals in the western region of Saudi Arabia. METHODS: We retrieved all cases diagnosed as RDD at King Abdulaziz University Hospital and King Faisal Specialist Hospital and Research Center, Jeddah, Saudi Arabia, diagnosed between January 2001 until June 2021. RESULTS: A total of 13 new RDD cases were reported, including 7 nodal and 6 extranodal type. The extranodal sites included larynx, optic chiasm, dura and brain, lumbar vertebrae, and left arm soft tissue.There were 6 males and 7 females. Ages averaged 34 years and ranged from 4-56 years. A total of 2 cases were associated with Hodgkin's lymphoma, and 2 cases have been initially misdiagnosed as other entities. All patients were treated with surgical excision, and steroid was added in 3 cases. Over 2-60 months of follow-up, recurrence occurred in 2 cases. CONCLUSION: Awareness of this entity is important for pathologists to avoid misdiagnosis. While the optimal treatment remains controversial, surgical resection is generally curative. The prognosis is good with rare recurrence. Multicenteer prospective studies are probably the best to evaluate treatment options and improve outcomes.

Experience of diagnosing and managing a patient with spinal Rosai-Dorfman-Destombes disease in a tuberculosis hyperendemic region.

Classic Rosai-Dorfman-Destombes disease (RDD) is a rare histiocytic disorder with bilateral massive painless cervical lymphadenopathy. It is a mysterious disease and there is little knowledge of its pathogenesis, clinical features, radiological findings, laboratory investigations, effective treatments and prognosis. Some of its clinical presentations may overlap with those of Mycobacterium tuberculosis infection. Just like tuberculosis infection, RDD may involve many other organs, for example, skin, kidney, bone, brain and spine. The diagnosis can easily be overlooked, especially in communities hyperendemic to tuberculosis infection. We report our experience in diagnosing and managing a patient with spinal RDD with concurrent tuberculosis infection, who was treated empirically for cervical tuberculous lymphadenitis without a conclusive laboratory finding prior to her spinal condition. In view of her acute neurological deficit, emergency spinal decompression was performed. Her intraoperative spinal samples had shown classic histopathological features of RDD. We believe the lymphadenopathy was part of the clinical presentation of RDD. She showed favourable neurological recovery throughout the follow-up.

Disease Characteristics, Radiologic Patterns, Comorbid Diseases, and Ethnic Differences in 32 Patients With Rosai-Dorfman Disease.

OBJECTIVE: Rosai-Dorfman disease (RDD) is a rare and idiopathic nonneoplastic disease of histiocytes that is characterized by lymphadenopathy and extranodal disease. In this study, we documented anatomical preferences, imaging findings, comorbid diseases, and ethnic differences in 32 RDD patients. METHODS: We conducted a retrospective review of pathologically confirmed cases seen at our institution from 1998 to 2016. These cases were analyzed for (a) anatomical locations, (b) radiologic appearance, (c) comorbid diseases, and (d) differences between ethnic groups. RESULTS: We found 32 patients with RDD, 18 were women and 14 were men. There were 51 lesions in all patients, 23.5% of which were nodal, involving 11 lymph node regions, and 76.5% were extranodal. Cervical lymph nodes and maxillofacial area were the most common affected nodal and extranodal locations, respectively. Only 4 (12.5%) of 32 patients had pure nodal involvement, whereas 20 (62.5%) of 32 had pure extranodal disease and 8 (25%) of 32 had mixed nodal and extranodal disease.Anatomically, RDD affected multiple organs in our cohort, including the lymphatic system, maxillofacial area (glandular and nonglandular tissues), superficial soft tissue, central nervous system, breast, peritoneum, gastrointestinal tract, and lungs.Radiologically, RDD presentation was variable from an organ to another. However, most lesions were hypermetabolic on 18F-fluorodeoxyglucose positron-emission tomography/computed tomography and isointense on T1-weighted magnetic resonance imaging. Computed tomographic findings were extremely variable between organs.Comorbid diseases were found in 11 patients. Those patients had 17 comorbid diseases; the most common were autoimmune diseases, viral diseases, and cancer.The organ distribution of RDD was slightly different between ethnic groups. The most frequent disease location for African Americans was lymph nodes; for whites, central nervous system and nonglandular maxillofacial (27.3% each); for Asians, lymph nodes, subcutaneous tissue, and nonglandular maxillofacial (25% each); and for Hispanics, lymph nodes and glandular maxillofacial (33.3% each). CONCLUSIONS: Rosai-Dorfman disease represents a wide-spectrum disease not limited to lymph nodes. Radiologically, RDD has diverse imaging findings. However, most lesions were hypermetabolic on 18F-fluorodeoxyglucose positron-emission tomography/computed tomography and isointense on T1-weighted imaging. Patients with RDD have a high rate of comorbid diseases including autoimmune disease, viral infections, and cancer.

Clinicopathological features, treatment approaches, and outcomes in Rosai-Dorfman disease.

Rosai-Dorfman disease is a rare subtype of non-Langerhans cell histiocytosis. With the last major report published in 1990, there is a paucity of contemporary data on this disease. Our objective was to report the clinicopathological features, treatments and outcomes of patients seen at a tertiary referral center. Sixty-four patients with histopathological diagnosis of Rosai-Dorfman disease were identified from 1994 to 2017 (median age 50 years; range, 2-79). The median duration from symptom onset to diagnosis was seven months (range, 0-128), which was also reflected in the number of biopsies required to establish the diagnosis (median 2; range, 1-6). The most common presentation was subcutaneous masses (40%). Of the 64 patients, 8% had classical (nodal only) and 92% had extra-nodal disease (67% extra-nodal only). The most common organs involved were skin and subcutaneous tissue (52%), followed by lymph nodes (33%). Three patients had an overlap with Erdheim-Chester disease, which had not been described before. Two of these were found to have MAP2K1 mutations. Commonly utilized first line treatments were surgical excision (38%) and systemic corticosteroids (27%). Corticosteroids led to a response in 56% of the cases. Of those treated initially, 15 (30%) patients developed recurrent disease. The most commonly used systemic agent was cladribine (n=6), with 67% overall response rate. Our study demonstrates that Rosai-Dorfman disease has diverse clinical manifestations and outcomes. While this disease has been historically considered a benign entity, a subset of patients endures an aggressive course necessitating the use of systemic therapies.

Rosai-Dorfman Disease: The MD Anderson Cancer Center Experience.

BACKGROUND: Rosai-Dorfman disease (RDD) is a rare disorder composed of a proliferation of histiocytes with varied clinical manifestations. PATIENTS AND METHODS: In this retrospective observational study, we obtained demographic, clinical, and outcome data from the medical records of 10 adult patients with RDD seen in the Department of Lymphoma and Myeloma at MD Anderson Cancer Center between 1995 and 2015. RESULTS: Patients had a median age of 56 years (range, 20-81 years) with equal gender distribution. Five patients were initially treated with systemic therapy. Five received cladribine as initial therapy or for relapse. Other therapeutic agents included clofarabine, lenalidomide, and steroids. The overall response rate was 80% in patients receiving cladribine, with a median progression-free survival of 29 months. Surgery, radiotherapy, and observation were also treatment options for localized disease. With a median follow-up of 65 months, none of the patients have died. CONCLUSION: Currently, there is no standard of care for RDD. Treatment should be personalized for each patient depending on the clinical presentation, course of the disease, and prior treatment history. Purine analogues provide excellent responses; however, surgical resection and observation are also suitable for specific cases.

[Rosai-Dorfman disease: Diagnosis and therapeutic challenges]. / La maladie de Destombes-Rosai-Dorfman : évolution du concept, classification et prise en charge.

Rosai-Dorfman disease (RDD) was first described by the French pathologist Paul Destombes in 1965. It frequently affects children or young adults and is characterized by the presence of large histiocytes with emperipolesis. More than 50 years after this first description, the pathogenesis of this rare disease is still poorly understood. The revised classification of histiocytoses published in 2016 identified various forms of RDD, from familial RDD to IgG4-associated RDD. Almost 90% of the patients with RDD have cervical lymph nodes involvement although all the organs may virtually be involved. Outcomes are typically favorable. Treatments may be necessary in case of compression or obstruction, and are not well codified. The main therapeutic strategies rely on surgery, radiotherapy, steroids, immunosuppressive drugs or interferon-alpha and cladribine.

Langerhans Cell Histiocytosis and Other Histiocytic Diseases of the Lung.

Several histiocytic disorders may affect the thoracic cavity. Pulmonary Langerhans cell histiocytosis (LCH) is the histiocytic disorder that most frequently manifests with thoracic involvement in adults and is associated with cigarette smoking. The histiocytic disorders follow variable clinical courses ranging from benign disease to life-threatening aggressive disorders. Although the pathogenesis is not fully understood, it is now apparent that some of these disorders are associated with activating mutations in cell proliferative/regulatory pathways. Management of these rare disorders must be individualized. Pharmacologic treatment may include the use of chemotherapeutic agents. Smoking cessation is imperative in the management of pulmonary LCH.

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.

Adult Xanthogranuloma, Reticulohistiocytosis, and Rosai-Dorfman Disease.

Adult xanthogranuloma presents most commonly as an orange-tan firm solitary nodule with no systemic manifestations. Recently, some cases have been reported in conjunction with lymphoproliferative disorders. Adult reticulohistiocytosis classically presents as red to yellow-red dermal nodules. In the multicentric form, lesions have a predilection for hands and elbows, with a classic coral bead periungual presentation, and are often associated with symmetric erosive arthritis, particularly of the hands and wrists. The presentation and course of Rosai-Dorfman disease, or sinus histiocytosis with massive lymphadenopathy, can vary. The classic presentation is extensive, painless bilateral cervical lymphadenopathy, but some cases have been entirely extranodal.

Co-occurrence of intracranial Rosai-Dorfman disease and Langerhans histiocytosis of the skull: case report and review of literature.

Rosai-Dorfman Disease involves histiocytic proliferation of the lymphatic system. Extranodal disease involving the central nervous system is uncommon. Furthermore, the combination of this disease entity with Langerhans cell histiocytosis is an even rarer phenomenon that has only recently been highlighted. A young male, who had previously undergone surgical excision of a skull lesion that was reported as Langerhans histiocytosis presented with an intracranial lesion mimicking a meningioma. Histopathology of the lesion was reported as being consistent with Rosai-Dorfman disease and the patient is currently undergoing chemotherapy. This is only the second report of the co-occurrence of Langerhans histiocytosis and Rosai-Dorfman disease in the cranium and intracranial cavity. The possibility that the diseases represent different spectra of the same underlying pathology is one that merits more detailed analysis, especially at the genomic level.

Involvement of the testis and related structures by Rosai-Dorfman disease: report of 2 new cases and review of the literature.

This report describes 2 new cases of testicular involvement by Rosai-Dorfman disease, also known as sinus histiocytosis with massive lymphadenopathy, and reviews the clinical and pathologic features of the other cases documented in the literature (4 cases) or included in the sinus histiocytosis with massive lymphadenopathy registry (7 cases). Our patients were 42 and 68 years of age, respectively, reflecting the usual middle-age of all the previously reported cases in this location, except for 1, which occurred in a child. Five cases were bilateral, and other sites, such as lymph nodes, kidney, skin, and adrenal gland, were involved in 8 cases. The histories were noteworthy in 2 of the cases, inasmuch as 1 patient had chronic lymphocytic leukemia, and another had a B-cell lymphoma. On gross examination, the testicular masses did not exhibit specific diagnostic features, whereas microscopic examination revealed the typical population of histiocytes, with abundant eosinophilic cytoplasm often exhibiting so-called emperipolesis. The differential diagnosis includes non-neoplastic conditions such as granulomatous orchitis, hematolymphoid disorders, a variety of metastatic tumors, and germ cell tumors.

Successful treatment with azathioprine of relapsing Rosai-Dorfman disease of the central nervous system.

Rosai-Dorfman disease (RDD) is a rare non-Langerhans histiocytosis that usually presents with lymphadenopathy. Although isolated involvement of the CNS was considered to be uncommon, numerous cases have been reported in recent years. For RDD of the CNS, the treatment consists, in general, of surgery. In cases of partial resection or relapse, chemotherapy regimens, corticosteroids, and/or radiotherapy have yielded negative results. The authors describe the case of a 57-year-old man with a history of chronic Q fever who presented with aphasia and partial seizure. Computed tomography of the brain revealed a left frontotemporal lesion that was suggestive of a meningioma. The lesion was partially resected and histopathological evaluation revealed the presence of RDD. Nineteen months later, a Jacksonian seizure prompted MRI evaluation, which disclosed a local recurrence of the tumor. Computed tomography and FDG-PET demonstrated that the RDD involved no other site, but the presence of ileitis, noted on ileoscopy, led to the diagnosis of Crohn disease. Treatment with the purine analog azathioprine was initiated, leading to an objective and sustained response in both the RDD tumor and ileitis over 35 months of follow-up. This case report highlights the potential use of a purine analog in cases of relapsing RDD of the CNS and a possible common defect of macrophage regulation in RDD, Crohn disease, and Q fever.

Coexistence of rhinoscleroma with Rosai-Dorfman disease: is rhinoscleroma a cause of this disease?

INTRODUCTION: Rhinoscleroma and Rosai-Dorfman disease have been reported to coexist in the same patient at different sites. Rosai-Dorfman disease may have an aetiological relationship with rhinoscleroma, although this has not yet been proved. CASE REPORT: A case of a 42-year-old woman with recurrent nasal masses is presented, with histopathological proof of both conditions coexisting in the same nasal lesion. DISCUSSION: The aetiopathology, clinical features and treatment of both diseases are discussed and a literature survey is reported. Histologically, the presence of Mikulicz cells with entrapped, rod-like, Gram-negative bacilli and Russell bodies suggests rhinoscleroma. Emperipolesis and S-100-positive histiocytes confirm the diagnosis of Rosai-Dorfman disease. The presence of both in the same slides from affected tissues has never been demonstrated before. In the light of this evidence, the author believes that rhinoscleroma must be considered in the aetiology of Rosai-Dorfman disease.

Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease) and oligoarthritis.

A 24-year-old woman who had sinus histiocytosis with massive lymphadenopathy (SHML, Rosai-Dorfman disease) also had oligoarthritis. We found only four previously reported cases of SHML with clinical joint disease. The clinical picture may suggest rheumatoid arthritis or a spondylarthropathy with peripheral joint involvement. SHML should be considered routinely among the differential diagnoses in young patients with arthritis and large lymphadenopathies. There is no consensus regarding the treatment. In our patient, conventional disease-modifying antirheumatic drugs followed by 3 months of adalimumab then 3 months of etanercept had no effect on the symptoms.

[Isolated intracranial Rosai-Dorfman disease: a case report and literature review]. / Enfermedad de Rosai-Dorfman intracraneal. Presentación de un caso y revisión de la literatura.

INTRODUCTION: Sinus histiocytosis with massive lymphadenopathy, also known as Rosai-Dorfman disease (RDD) is an idiopathic histiocytosis that usually affects the lymph nodes. Occasionally it may affect the CNS, being exceptional intracranial involvement without lymph node lesions. In the absence of typical radiological signs, affected patients are generally operated under the suspicion of a meningioma. The histological diagnosis is obtained after the surgical procedure. It is a clinicopathological entity not well known, controversy exists about its pathogenesis, clinical course and therapeutic management. CASE REPORT: We report the case of a 40-year-old male presented two generalized tonic-clonic seizures and brain MRI showed a left parieto-occipital extra-axial lesion extending into the posterior fossa, without presenting lesions at other levels. A partial resection of the lesion was performed and the histological findings were reported as Rosai-Dorfman disease. CONCLUSIONS: Despite its low frequency, the ERD should be included in the differential diagnosis of dural-based masses, compared to more common, such as meningiomas. Due to lack of specificity of additional studies its diagnosis is fundamentally histologic. More research is needed to define the best therapeutic option.

[Mammary gland Rosai Dorfman disease. A case report and literature review]. / Enfermedad de Rosai-Dorfman en glándula mamaria. Informe de un caso y revisión de la literatura.

Rosai-Dorfman disease (RDD) is an uncommon idiopathic, benign histiocytic lesion. It generally involves the cervical lymph nodes and, less often the extranodal sites. Involvement of the breast is rare, with about 18 cases reported in the English literature to date. We describe a case of breast involvement by extranodal RDD. The patient was a 67 year old woman with a solid breast lesion that was detected during mammography screening. Microscopically, the lesion was well-circumscribed, and made of sheets of S-100 protein-positive large histiocytes displaying lymphocytophagocytosis. Because the clinical presentation and imaging characteristics of RDD frequently mimics invasive breast carcinoma, awareness and appropriate diagnosis of this entity is essential for proper treatment.

Clinicopathologic characteristics of Rosai-Dorfman disease in a medical center in northern taiwan.

BACKGROUND/PURPOSE: Rosai-Dorfman disease (RDD) is a rare histiocytic proliferative disorder that usually presents as cervical lymphadenopathy. Extranodal involvement occurs in up to 40% of patients. The disease is most prevalent in blacks and rare in Asians. This study analyzed the characteristics of RDD in patients from Taiwan. METHODS: Fourteen patients with a diagnosis of RDD were identified by review of records from 1995 to 2004 at National Taiwan University Hospital. Tissue sections from each patient were reviewed and immunohistochemical staining was performed. Data on clinical presentations, associated diseases, treatment and outcome were analyzed. In situ hybridization for Epstein-Barr virus (EBV)-encoded small RNAs (EBER-1) was also performed. Sets of primers specific for the conservative region of bacterial 16S-rDNA, IS6110 of Mycobacterium tuberculosis complex and consensus region of human herpes virus (HHV) DNA polymerase genome were used to detect the presence of these infectious agents in the specimens. RESULTS: There were six men and eight women with a mean age of onset of 44 years. Nine patients presented with skin lesions, four with lymph node involvement and one with nasal tumor. All lesions followed a chronic and indolent course. Most of the lesions regressed spontaneously, and no patients died as a result of this disease during follow-up. Three patients had associated immune-mediated disease, i.e. hemolytic anemia, ankylosing spondylitis and asthma. Two patients had a history of tuberculosis. Histologically, all lesions were characterized by a mixed infiltrate of large pale histiocytes, abundant plasma cells and lymphocytes regardless of the site of involvement. The strong immunoreactivities of these histiocytes to S-100 protein, CD68 and CD14 with occasional lymphophagocytosis were helpful in confirming the diagnosis, polymerase chain reaction analysis of 16S-rDNA, IS6110 and HHV gene and in situ hybridization for EBV were all negative. CONCLUSION: RDD in Taiwan is characterized by older age of onset compared to Western countries (44 years vs. 20 years) and more frequent extranodal involvement. The skin was the most common site of extranodal involvement, with about two-thirds of patients presenting with cutaneous lesions. There was no evidence of bacterial, mycobacterial or HHV infection in this series.