Isolated localization of Rosai Dorfman disease as renal mass: a case report and review of literature

We report a rare case of an elderly woman presented with right renal mass with invasion of renal vein and several small lymphadenopathy in the hilar area. The diagnosis of kidney cancer is suspected and the patient underwent open radical nephrectomy, surrenalectomy and lymphadenectomy dissection. The pathologic examinations find a rosai dorfman disease. This unusual benign entity is uncommon in the kidney, but in medical imaging, it may simulate an infiltrative renal neoplasm, especially a lymphoma or leukemia or even renal cell carcinoma. A comprehensive literature review was undertaken to summarize the clinical and pathologic features of this disorder.


Introduction
Rosai-Dorfman disease (RDD) or sinus histiocytosis is a rare benign disease of unknown etiology. Classically, it is characterized by lymphadenopathy mainly in the cervical area associated with fever, leukocytosis, polyclonal gammopathy, and an elevated erythrocyte sedimentation rate. Histopathologically an inflammatory proliferation of S 100 protein-positive histiocytes characterized by lymphophagocytosis is seen. Most cases involve patients in their first and second decades, but all age groups can be affected [1,2].
Extranodal sites are involved in 43% of cases, and lymphadenopathy may be absent in such patients [3] .We report a case of a woman with a Rosai Dorfman disease presenting as extranodal renal mass. We review the clinical presentation and essential histopathologic features necessary for the accurate diagnosis of this disease.

Patient and observation
68-year-old woman presented with hematuria and right flank pain

Discussion
Rosai-Dorfman disease or sinus histiocytosis with massive lymphadenopathy was first described in 1969 by Rosai and Dorfman. It is classified as a non-neoplastic histiocytic disorder and is classically characterized by massive lymphadenopathy secondary to infiltration and dilation of the lymph node sinuses by large histiocytes, mainly in the cervical area.
Generally manifests in children or young adults with massive cervical lymphadenopathy, fever, leukocytosis, an increased erythrocyte sedimentation rate and hypergammaglobulinemia. Other lymphatic groups such as mediastinal, axillary and inguinal lymph nodes can also be affected [2]. The etiology is unknown, although an infectious or chronic inflammatory cause has been implicated. It is also known that clinically significant immunologically mediated disease can occur in association with sinus histiocytosis with massive lymphadenopathy and may adversely affect the prognosis.
Extranodal disease has been reported in 43% [3]. Kidney involvement is very uncommon, and therefore sinus histiocytosis is not frequently considered in the differential diagnosis of an infiltrative renal mass.
To our knowledge there only four cases of RDD in kidney cases have been reported with two of them diagnosed with adenocarcinoma of the prostate. In a rare case reported by Buchino et al, the kidney was only focally involved with a single small mass in the lower pole that contained an admixture of histiocytes, lymphocyte and plasma cells [4]. In another case reported by Bechtold et al, a lobular irregularly enlarged kidney with distorted calyces associated with large matted para-aortic lymph nodes was described and the diagnosis was RDD [5]. Associated symptoms and signs may be caused by specific organ involvement or may be constitutional, such as fever and weight loss. presence of intact lymphocytes, plasma cells, neutrophils, and red blood cells) within histiocytes is the pathognomic feature [6].
Immunohistochemistry shows the positivity for S-100 and CD68 and the negativity for CD1a [7].
The differential diagnosis of RDD in kidney includes malignant fibrous histiocytomas and histiocytic proliferations of infectious etiology (the presence of S100 is useful in discriminating these lesions), leukemia or lymphoma, especially when accompanied by

Conclusion
Rosai-Dorfman disease of the kidney, although rare, should be considered in the differential diagnosis of renal mass especially when it is bilateral .in computed tomography scan The appearance can resemble renal cell carcinoma and lead to radical nephrectomy.

Competing interests
The authors declare no competing interests.

Authors' contributions
All authors have read and agreed to the final version of this manuscript and equally contributed to its content and to the management of the case.