Discussion
In 1969, two pathologists Juan Rosai and Ronald Dorfman reported a distinct histiocytic disorder in young black males presenting with bilateral, painless, massive cervical lymphadenopathy with a protracted clinical course, and in most instances associated with fever, anemia, neutrophilia, elevated erythrocyte sedimentation rate, and polyclonal gammopathy[
1]. The clinicopathological conglomerate that they named sinus histiocytosis with massive lyphadenopathy has now come to be known as Rosai-Dorfman disease[
1]. Subsequently it became clear that the disease had no specific predilection for geographic location or race [
5].
Painless lymphadenopathy is the most frequent systemic presenting symptom and involves the cervical region in up to 90% of patients [
5]. Other locations such as inguinal (26%), axillary (24%) and mediastinal lymph nodes (15%) are also reported to be involved [
5].
Extranodal disease is documented in 43% of patients, in some without associated lymphadenopathy, which may or may not develop later in the disease course [
5]. The most common extranodal sites, in the decreasing order of frequency, are skin, nasal cavity and paranasal sinus, eyelid, orbit, bone, salivary gland and central nervous system [Additional File
2] [
5]. The simultaneous involvement of multiple extranodal sites is not unusual [
5]. Hepatosplenomegaly, unlike in other histiocytic disorders, is uncommon [
5].
The high prevalence of this disease in this series (2.3% of orbital lesions and 0.09% of ocular specimens) is possibly because this center is a tertiary eye referral center with a dedicated Ocular Oncology Service. With increasing number of ocular specimens received at our centre to nearly 4,000 samples per year, the prevalence may now match the same as seen in any general hospital, i.e 0.03% [5/15,000 cases based on the personal communication received from a surgical pathologist ]. The reported ophthalmic manifestations of Rosai-Dorfman disease include orbital and eyelid involvement, lacrimal gland involvement, optic nerve compressive neuropathy and uveitis [
3,
6‐
12]. Orbital involvement is the most common of ophthalmic manifestations [
3,
6‐
12]. While a majority of patients with orbital involvement have concurrent lymphadenopathy, some may present with orbit as the sole extranodal site of involvement without synchronous nodal disease, and a minority may have concurrent involvement of other extranodal sites such as the paranasal sinus [
3]. In our series of seven patients, six were under 20 years of age and had chronic symptoms ranging from 3–15 years. All had painless progressive proptosis and two had an eyelid mass. Four patients had bilateral manifestations, 4 had synchronous nodal disease and 3 had concurrent extranodal involvement.
Clinical laboratory findings in Rosai-Dorfman disease include hematological abnormalities such as normocytic or microcytic anemia, hemolytic anemia, elevated erthrocyte sedimentation rate and polyclonal hypergammaglobulinemia [
5]. Two patients in our series had normocytic hypochromic anemia. However, erythrocyte sedimentation rate was within the normal range in all patients and serum electrophoresis did not reveal hypergammaglobulinemia.
According to the Writing Group of the Histiocyte Society [
13], the histiocytic syndromes can be subdivided based on whether the proliferating histiocytes are the Langerhans cells or not and whether the process is benign or malignant. Rosai-Dorfman disease is one of the non-Langerhans cell benign histiocytosis where predominantly the sinuses of the lymph nodes, and less commonly the interfollicular area of the lymph nodes are infiltrated with distinctive histiocytes with round or oval vesicular nuclei with well-defined, delicate nuclear membranes and a single prominent nucleolus [
1,
2,
5]. Nuclear atypia and mitoses are infrequent. The hallmark of Rosai-Dorman disease is lymphophagocytosis or emperipolesis, wherein the viable lymphocytes are located in well-defined cytoplasmic vacuoles of intact histiocytes. Plasma cells, neutrophils and red blood cells may also occupy this unique intracytoplasmic niche. The involved histiocytes are activated macrophages with features of phagocytic cells as well as immune accessory cells and thus express S-100 protein, HAM 56, α1 antitrypisn, α1 chymotrypsin, lysozyme, Mac 387, Ki-1 (CD 30, Ber-H2), but are negative for CD 1a (leu 6) [
14]. Rosai-Dorfman disease involving extranodal sites shows similar morphologic features to its nodal counterpart with more fibrosis and fewer histiocytes with emperipolesis. The histological differential diagnosis includes hemophagocytic syndromes, storage disorder, inflammatory lesions, necrobiotic xanthogranuloma and lymphoreticular malignancies [
15]. The presence of benign histiocytes with emperipolesis, absence of cellular atypia, immunohistochemical profile, and associated clinical features distinguish Rosai-Dorfman disease from other simulating disorders.
Cytologic features of Rosai-Dorfman syndrome are well recognized and the role of fine-needle aspiration cytology in its diagnosis has been demonstrated [
16,
17]. We used the impression cytology technique for rapid intraoperative diagnosis of Rosai-Dorfman disease based on known cytological characteristics in 4 patients in this series. The cytologic diagnosis correlated with the final histopathology in all four patients.
Despite its well-recognized clinical presentation, the precise etiology of Rosai-Dorfman disease remains unknown. The etiologic factors implied in the pathogenesis of this disease are bacterial (Klebsiella), virus (Epstein barr virus, parvovirus B 19), immune dysfunction, or an aberrant response to an unspecified antigen, HHV-6 or EBV [
18‐
21]. Current thinking is that the defective Fas/FasL signaling leading to altered apoptosis may be an important mechanism whereby uncontrolled histiocytic proliferation is triggered [
20]. The presence of characteristic histiocyte, derived from circulating mononuclear cells, long history and an increased incidence of serum autoreactive antibodies during active disease suggest a possible pathogenic correlations with a dysregulatory process. In a recent report, the evidence points towards a viral etiology as suggested by the immunolocalization of parvovirus B19 (B19) virus using antibodies against B19 capsid proteins VP1/VP2[
21]. The relative increase of cases from this part of the world, also prompts us to believe that there could be a possible environmental factor, thereby warranting further studies in this direction. Though not done in this series, immunological studies, specifically for viral etiology, liver function along with follow-up to identify known risk factors like airway compression, would be beneficial in understanding more about this rare disease [
21,
22].
The clinical course of Rosai-Dorfman disease is chronic and variable with episodes of exacerbation alternating with periods of remission, where the timing and duration of each phase is entirely unpredictable. Foucar et al reported stable disease in 54%, spontaneous regression in 21%, and progressive disease in only 1% [
5].
The ideal treatment for Rosai-Dorfman disease is yet unestablished. Only about 50% of patients with Rosai-Dorfman disease need some form of treatment [
20]. Management options include observation for mild manifestations with no cosmetic or functional abnormality, surgical excision or debulking for lesions in surgically accessible locations, and systemic corticosteroids, chemotherapy or radiotherapy in patients with severe symptoms where vital organ function is compromised [
23‐
27]. Radiotherapy and antimetabolite treatment has been considered in a few cases but the literature review by Pulsoni et al does not suggest any conclusive role of these treatment modalities [
27]. The treatment of orbital manifestations of Rosai-Dorfman disease aims to control the functional and cosmetic abnormalities. Orbital involvement, being cosmetically disturbing and surgically accessible, may be more often considered for surgical treatment. Massive or recurrent orbital disease or significant residual lesion following surgical debulking may be treated with systemic corticosteroids, chemotherapy or radiotherapy. Chemotherapy has also been used to relieve the sight threatening optic nerve compression [
10].
All patients in our series underwent surgery – 3 with well-defined localized mass underwent surgical excision and 3 with diffuse orbital involvement and 1 with lacrimal gland involvement underwent an incisional biopsy. Three patients with diffuse orbital involvement received systemic corticosteroid therapy. Local recurrence was noted in 2 of 7 (29%) cases, both within one year of primary treatment, and these patients responded to systemic corticosteroids.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
GKV conceived the idea, carried out the histopathologic studies, drafted the manuscript and reviewed the review of literature, MN participated in the study design, and reviewed the cases, SGH participated in the study design and provided critical inputs into the study. All authors read and approved the final manuscript