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Original Report |
1 Department of Radiology and Institute of Radiation Medicine, Seoul National
University College of Medicine.
2 Department of Radiology, Seoul National University Bundang Hospital, 300
Gumi-dong, Bundang-gu, Seong Nam, Gyeongi-Do, 463–707, Korea.
3 Department of Radiology, Yonsei University College of Medicine, Seoul,
Korea.
4 Department of Radiology, Samsung Medical Center, Sungkyunkwan University
College of Medicine, Seoul, Korea.
5 Department of Radiology, Pusan Paik Hospital, Inje University College of
Medicine, Pusan, Korea.
6 Department of Radiology, Yeungnam University College of Medicine, Gyeong-San,
Gyeongsangbuk-Do, Korea.
7 Department of Radiology, Chonnam University College of Medicine, Gwangiu,
501-190, Korea.
Received February 17, 2004;
accepted after revision May 13, 2004.
Address correspondence to H. S. Kang
(kanghs{at}radcom.snu.ac.kr).
Abstract
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CONCLUSION. Kimura's disease should be considered as a possible diagnosis when a partially or poorly defined subcutaneous mass of high signal intensity on T1- and T2-weighted images with homogeneous enhancement, surrounding subcutaneous edema, and internal flow voids is seen in the medial epitrochlear region in an Asian person, especially if accompanied by peripheral eosinophilia.
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The exact cause of Kimura's disease is still unknown; the histopathologic and laboratory findings suggest an inflammatory response associated with a self-limited allergic or an autoimmune reaction to a stimulus unknown as yet [3, 12]. However, the course of the disease is thought to be benign, despite its common recurrence and controversy about therapy [12].
In the literature, there has been confusion about whether Kimura's disease and other disease entities are variants of the same disease, including angiolymphoid hyperplasia with eosinophilia, epithelioid hemangioma, angiofollicular lymphoid hyperplasia, low-grade angiosarcoma, atypical or pseudopyogenic granuloma, and eosinophilic granuloma of the soft tissues; however, researchers recently suggested that Kimura's disease is a unique disease entity with distinct clinicopathologic features [2, 3, 10, 13, 14].
Imaging findings of Kimura's disease occurring in the head and neck region have been reported [3–8], but imaging findings of Kimura's disease involving the upper extremity have not been reported, to our knowledge, in the literature; thus, Kimura's disease almost never is considered as a differential diagnosis for a soft-tissue mass in the upper extremity to our knowledge.
The purpose of this study was to describe the imaging findings of pathologically confirmed Kimura's disease in the upper extremity.
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Imaging studies included radiographs and MR images of the upper extremity mass in all nine patients. Two of the patients also underwent contrast-enhanced CT. Because imaging studies were performed at outside institutions, the MRI systems and pulse sequences varied and were performed using 1.0- and 1.5-T scanners. However, spin-echo T1-weighted (TR/TE, 400–560/12–25), fast spin-echo T2-weighted (3,120–4,500/60–105), and gadolinium-enhanced T1-weighted images were available in all cases. Axial images were obtained in all cases, and most also included either sagittal and coronal images or both. The fat-suppression technique was used for fast spin-echo T2-weighted images in two patients and for gadolinium-enhanced T1-weighted images in seven patients.
Imaging studies of each lesion were reviewed retrospectively, and a consensus was rendered by three musculoskeletal radiologists. Imaging features were evaluated for anatomic location, margination, CT attenuation and MR signal intensity characteristics, presence and pattern of contrast material enhancement on CT and MRI, presence of edema, and involvement of an adjacent structure. The criteria for evaluation were modified from those in a previous report [15]. The evaluation of the anatomic location included whether the mass was centered within muscle, subcutaneous tissue, or a joint. The margin of the lesion was considered well defined if more than two thirds of the margin was sharply demarcated from the surrounding tissue and poorly defined if less than one third of the margin was sharply defined. Intermediate cases were considered partially defined. The determination of margin characteristics was made on the basis of the image with the greatest contrast between the mass and the surrounding tissue. The same definition for margination was used for evaluation of both MR images and CT scans.
Skeletal muscle was used as the reference tissue for CT attenuation. The signal intensities on T1- and T2-weighted images were compared with the adjacent skeletal muscle as well. The degree of enhancement was graded subjectively but in consensus as none, mild, moderate, or good compared with normal adjacent skeletal muscle. In addition, the pattern of enhancement was classified as homogeneous or heterogeneous. Edema was considered to be present when infiltrative, streaky high signal intensities on T2-weighted images could be seen extending from the margins of the lesion into the surrounding tissues. Involvement of adjacent structures was assessed for signal alterations in adjacent muscle, neurovascular structures, bones, and joints.
After imaging studies, all nine patients underwent excision of their epitrochlear masses at the institution of origin, and the final diagnosis was made on the basis of the pathology reports for the excision specimens.
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In all patients, CT scans and MR images showed a partially or poorly defined subcutaneous mass in the epitrochlear region, adjacent to the medial neurovascular bundles with signal intensity similar to or slightly higher than that of muscle on T1-weighted images and high relative to muscle on T2-weighted images. The masses showed moderate to good homogeneous enhancement. In all cases, variable stranding in the surrounding subcutaneous tissue and serpentine signal voids within the mass were seen. Laboratory data showed peripheral eosinophilia in all patients.
In all nine cases, the lesions were seen as a bulging soft-tissue masslike density at the medial epitrochlear region on radiographs with increased thickening of the surrounding soft tissue; no definite change, such as erosion or periosteal reaction or invasion, was noted in the adjacent bone.
The two available CT scans showed well-defined, isodense soft-tissue masses in the medial epitrochlear region that were enhanced moderately and homogeneously with well-enhancing internal vascular structures after IV administration of contrast material (Figs. 1A, 1B, 1C, 1D, and 1E).
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The MRI findings of these cases are summarized in Table 1. The MR images of all nine cases showed a soft-tissue mass in the subcutaneous fat layer of the medial epitrochlear region adjacent to the medial neurovascular bundles with surrounding edema. The margins were partially defined in five cases and poorly defined in four cases. In all cases, the masses showed iso- or slightly higher signal intensity relative to muscle on T1-weighted images and high signal intensity relative to muscle on T2-weighted images (Figs. 1A, 1B, 1C, 1D, and 1E). Gadolinium-enhanced T1-weighted images showed homogeneous enhancement of the mass in all nine cases (Figs. 1A, 1B, 1C, 1D, and 1E). In all cases, dotlike or tubular signal voids were observed within the mass, suggesting the presence of vascular structures. In all cases, there was stranding in the surrounding soft tissue, displaying increased signal intensity on T2-weighted images, suggestive of edema. In three patients, series of conglomerated, homogeneously well-enhancing soft-tissue masses were seen (Figs. 2A, 2B, 2C, and 2D). The masses compressed and slightly displaced the surrounding muscle and neurovascular bundles without definite signal changes in the adjacent muscle, neurovascular bundles, bones, and joints.
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The diagnosis of Kimura's disease was confirmed in all patients by means of pathologic review of an excisional biopsy specimen. Findings of all nine pathologic specimens were consistent with Kimura's disease. The gross lesion specimens were composed of nodular enlarged lymph nodes with surrounding fibrofatty connective tissue. Microscopic examination of the involved lymph nodes showed hyperplastic lymphoid follicles with prominent germinal centers. Mantle zones were well defined. Abundant eosinophilic infiltration in the paracortical area and prominent postcapillary venules were noted (Figs. 3A and 3B).
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The previously reported imaging findings of Kimura's disease in the head and neck region were nonspecific and variable [3–7, 12, 21–23]. On CT scans, subcutaneous masses with lymphadenopathy were reported as the typical findings [3]. The density of the masses varied from iso- to hyperdense [4, 6, 22]. On contrast-enhanced CT, enhancement patterns varied from mild to intense and from homogeneous to heterogeneous [3, 5–7, 12, 22, 23]. On MRI, the masses were reported to show variable signal intensity—that is, low or intermediate or mixed or high signal intensity on T1-weighted images and low or high signal intensity on T2-weighted images [3–6, 21, 23]. One case report about MRI findings described internal flow voids within the mass that suggested hypervascularity [3]. A few reports of patients with the disease described sonography findings as hypoechoic or heteroechoic masses and nodes with well- or ill-defined margins [22, 24]. The degree of enhancement on CT scans and the signal intensity on MR images were thought to vary, probably because of different degrees of fibrosis and vascular proliferation [4, 6].
In contrast to the variable and nonspecific imaging findings of Kimura's disease in the head and neck region, the imaging findings of Kimura's disease in the upper extremity showed some consistent features in this study. In all our cases, Kimura's disease in the upper extremity consistently was located in the subcutaneous fat at the medial epitrochlear region. In all cases, surrounding edema was noted around the masses. On CT scans, all the masses were isodense and showed homogeneous enhancement. On MR images, all the masses showed signal intensity similar to or slightly higher than that of muscle on T1-weighted images and high signal intensity relative to muscle on T2-weighted images. On gadolinium-enhanced T1-weighted images, homogeneous enhancement and signal-void structures within the mass were observed in all cases. Margins were partially or poorly defined.
On the basis of the imaging findings, the list of differential diagnoses for Kimura's disease in the upper extremity, similar to the list for the disease in the head and neck, includes various inflammatory and tumorous conditions, such as tuberculous lymphadenopathy, cat-scratch disease, lymphoma, metastasis, and soft-tissue sarcomas [3–7, 16, 25].
In tuberculous lymphadenopathy and metastasis, the lymphadenopathy shows central low density and peripheral rim enhancement [5, 26] usually without associated stranding in the soft tissue in contrast to the imaging findings of our cases. Imaging findings of cat-scratch disease show epitrochlear adenopathy with extensive surrounding subcutaneous edema similar to that seen in Kimura's disease; however, the absence of necrotic areas in the lymph node on enhanced images, no history of exposure to a cat, and negative serologic results help exclude cat-scratch disease [25]. Lymphoma usually manifests as multiple well-defined homogeneous nodules with uniform enhancement, but lymphadenopathy is commonly bilateral and diffuse with eccentric cortical hypertrophy and without surrounding soft-tissue change [5], offering a different picture from the cases in this study.
In this study, the consistent location of the soft-tissue mass in the epitrochlear region corresponded with involvement of the lymphatic chain adjacent to the medial neurovascular bundles. In three patients, conglomerated soft-tissue masses were seen, indicative of chains of enlarged epitrochlear lymph nodes. The lesions of Kimura's disease are characterized histopathologically by prominent germinal centers in involved lymph nodes with cellular, vascular, and fibrous components, consisting of dense eosinophilic infiltrates in a background of abundant lymphocytes and plasma cells, eosinophilic microabscesses with central necrosis, Warthin-Finkeldey-type polykaryocytes and vascular proliferation of germinal centers, increased postcapillary venules in the paracortex, and sclerosis without arteriovenous shunts [3, 11, 12, 27]. Immunofluorescence studies have revealed IgE deposits in the follicle centers [3, 12, 27]. Noncircumscribed inflammatory infiltrates within extranodal subcutaneous tissues and skeletal muscles associated with reactive germinal center formation and eosinophilic microabscesses and associated reactive lymphadenopathy also have been described as characteristic features of Kimura's disease [12]. At microscopic examination of the samples in this study, hyperplastic follicles with prominent germinal center and prominent mantles and diffuse eosinophilic infiltration, and vascular proliferation were noted (Figs. 3A and 3B); these findings are consistent with previously described findings of the disease in the head and neck region; however, fibrosis was noted rarely. This may explain the absence of low signal intensity of the lesions on T1- and T2-weighted images. Abundant vascular proliferation may explain the presence of enhancement and signal-void structures on MR images. Edematous change of subcutaneous soft tissue in the surrounding soft tissue was proven to be proliferation of lymphoid follicles in the subcutis at histology.
Even though imaging findings of Kimura's disease are nonspecific, Kimura's disease should be considered as a possible diagnosis when a partially or poorly defined subcutaneous mass with iso- or high signal intensity on T1- and T2-weighted images with homogeneous enhancement, internal flow voids, and surrounding subcutaneous edema is seen in the medial epitrochlear region of an Asian person, especially if accompanied by peripheral eosinophilia.
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