CD is an unusual non-neoplastic lymphoproliferative disorder which was first described as a disease entity in 1956.1
It has been called angiofollicular lymphoid hyperplasia, giant lymph node hyperplasia and angiomatous lymphoid hyperplasia in the past.5
The cause is undetermined but is most likely related to abnormal follicular dendritic cells.
CD arises primarily in the mediastinum, and about 70% of the reported cases tend to be of mediastinal origin, followed by lymph nodes in the abdomen, neck, and other sites.3
Retroperitoneal and pararenal localizations are very rare and CD of the kidney is extremely rare.4
To the best of our knowledge, fewer than 5 cases of CD involving the kidney that are of the localized HV type have been published in the English and Japanese literature.4
From the 1980s to 2010s, CD has been reported in Korea for more than 80 times. Of these, fewer than 15 occurred in the retroperitoneal area and only 2 in the kidney. All renal cases of CD were PC type.8
Our case is a HVCD involving renal parenchyma and a paraaortic lymph node simultaneously.
CD has been generally subclassified based on histologic features into HV, PC, and mixed type. More recently, a plasmablastic variant has been described as a fourth subtype.3
However, its clinical significance is determined by another classification of extent that is localized or multicentric.5
Nearly all cases of HV type (about 80%) and a minority of PC types (about 20%) are localized, which implies that the disorder affects a single anatomic site or a single group of lymph nodes. A localized HV type usually occurs in young people and is asymptomatic and associated with a benign clinical course. It is characterized by giant lymphoid follicles with small, regressively transformed hyalinized germinal centers and interfollicular vascular proliferation. Localized PC type usually affects mediastinal or intra-abdominal lymph nodes. This type has sheets of mature plasma cells in the interfollicular area and associated symptoms and laboratory abnormalities, such as anemia, fever, weight loss, night sweats, hypergammaglobulinemia, hypoalbuminemia and elevated ESR. Following excision of the mass, the abnormalities disappear, and the patients tend to do well overall.3
By contrast, multicentric CD (MCD) is a systemic disease with lesions of two or more separate anatomic sites.3
MCD was first proposed in 1983 by Frizzera et al.10
Recently, MCD has been defined as "a systemic disease with multiple peripheral lymphadenopathy or multiorgan involvement."10
However, another recent studies suggested that MCD is often composed of several disease entities, including idiopathic MCD and secondary MCD due to HIV infection, autoimmune disease-associated lymphadenopathy, POEMS (polyneuropathy, organomegaly, endocrinopathy, anasarca, M-proteins and skin lesions) syndrome, and non-Hodgkin lymphomas.11
Multicentric forms usually have histologic features of the PC type and only rarely of the HV type. Systemic symptoms tend to be more severe than those in localized PC type. The deregulated overproduction of IL-6 is responsible for symptoms. The levels of IL-6 appear to correlate with the systemic inflammatory manifestations.3
Recent reports suggested that HHV-8 has a viral homologue of human IL-6 in its genomic DNA, and HHV-8 infection stimulates B lymphocytes to induce IL-6 production. Moreover, other exogenous or endogenous factors may induce IL-6 secretion from B lymphocytes in HHV-8 negative CD.12
Nearly all HIV-positive patients and about half of HIV-negative patients with MCD have evidence of HHV-8 infection.3
However, Suda et al.13
reported that HHV-8 appears to be unrelated to the etiology of idiopathic MCD in Japan. Idiopathic MCD in Japan usually exhibits a chronic disease course, and appears to be related to a negative outcome for HHV-8 infection.
As above, MCD lacks a clear definition to date and there are various applications. In this regard, although our case had no significant systemic symptoms, we think it can be considered as MCD, at least from an anatomic point of view.
In summary, we report a very rare case of the multicentric HVCD involving the renal parenchyma and the paraaortic lymph node at the same time. The patient presented with a renal mass without evidence of HHV-8 infection and systemic symptoms. A few cases of multicentric HVCD have been reported before,14
but the renal location with involvement of regional lymph node has not been reported before in Korea.