Keywords
Kimura’s disease - diffusion weighted imaging - Contrast-enhanced magnetic resonance
imaging - magnetic resonance imaging
Introduction
Kimura’s disease is a chronic inflammatory disorder of the subcutaneous tissues of
the head and neck region. Seen predominantly in the eastern hemisphere, its key pathologic
feature is lymphoid follicles rich with eosinophils. Owing to its rare occurrence
and clinico-radiologic similarity with various other common disease processes, it
is a frequently misdiagnosed entity in the initial stages of evaluation. In the current
era of high-volume cross-sectional imaging of head and neck pathologies, imaging appearance
of Kimura’s disease needs consideration. In this case report, we describe the magnetic
resonance imaging (MRI) features in an adult male with Kimura’s disease of the parotid
region.
Case Report
A 36-year-old man presented with gradually progressive recurrent painless swelling
in the right postauricular region for the past 1 year. He had a similar swelling 10
years back, which was operated upon and confirmed to be Kimura’s disease on histopathologic
examination of the excised specimen. At present, the hemogram revealed elevated eosinophil
count (relative eosinophil count of 14.9% and absolute eosinophil count of 750 cells
per microliter). In this case of recurrent Kimura’s disease involving the right parotid
region, multiplanar and multisequence contrast-enhanced MRI was done on a 3.0 T MRI
scanner (Discovery™ MR750, GE Healthcare, Milwaukee, USA). After the acquisition of
routine sequences, intravenous injection of gadodiamide at a dose of 0.1 mmol/kg was
administered and three-dimensional (3D) fat-suppressed T1-weighted sequences were
acquired at 4 and 20 min after contrast injection.
The axial T2-weighted images showed a predominantly hyperintense, heterogenous infiltrative
lesion located posterior to the right parotid gland and infiltrating into its posterior
border [Figure 1]. Few tiny signal intensity voids were noted within this lesion, indicative of vessels.
There was no deeper infiltration beyond the subcutaneous plane; however, multiple
associated enlarged and hyperintense lymph nodes were noted in the right posterior
cervical region (level V). Enlarged intraparotid lymph nodes were also noted. On evaluating
the diffusion weighted images (DWI) at b value of 1000 s/mm2, the subcutaneous lesion showed increased signal intensity compared to the normal
parotid gland [Figure 2]. On DWI, the associated intraparotid and cervical lymph nodes showed homogenously
increased signal intensity, which was higher than the subcutaneous periparotid lesion.
On corresponding apparent diffusion coefficient (ADC) maps, the degree of hypointensity
of the lymph nodes was more compared to the subcutaneous periparotid lesion. The mean
values and standard deviation of the ADC values of the subcutaneous lesion and lymphadenopathy
were 1.76 ± 0.142 and 0.812 ± 0.06 mm2/s respectively. The contrast-enhanced images acquired at 4 and 20 min after contrast
injection showed significant difference between the two entities [Figure 3]. The subcutaneous lesion showed progressively increasing enhancement on comparing
the 4 and 20 min post contrast images. The lymphadenopathy, on the contrary, showed
progressive fading of contrast enhancement at 20 min.
Figure 1 (A-D): Axial T2 weighted images. (A) A heterogeneously hyperintense subcutaneous lesion
is noted in the right posterior periparotid region with indistinct posterior margin
of the parotid gland along the line of contact, suggestive of early infiltration.
(B) Small circular and tubular signal voids are seen within the subcutaneous lesion
due to vessels within it (thin white arrow). Also note the enlarged intraparotid lymph node (block white arrow). (C) The enlarged and homogenously hyperintense posterior cervical lymph nodes can
be seen (thin white arrow). Note the normal size and signal intensity of the right sternocleidomastoid muscle
(white star) separating the subcutaneous lesion and the enlarged posterior cervical lymph nodes
confirming the lack of deeper infiltration of the subcutaneous lesion. (D) An entire
chain of enlarged and hyperintense right-sided posterior cervical lymph nodes can
be seen deep to the sternocleidomastoid muscle
Figure 2 (A-D): Diffusion weighted images and ADC maps. (A and B) The signal intensity of the subcutaneous
lesion (block white arrow) is higher than the normal parotid gland parenchyma (star) on both sides but less than that of the disease associated enlarged right intraparotid
(thin white arrow) and right posterior cervical (block arrowhead) lymph nodes. (C and D) The ADC maps corresponding to the DWI in (A) and (B) show
most marked hypointensity (reduced ADC values) in the enlarged right intraparotid (thin white arrow) and posterior cervical (block arrowhead) lymph nodes. Thus, the disease associated enlarged lymph nodes in the Kimura’s disease
show homogenous diffusion restriction. The subcutaneous lesion (block white arrow), however, does not show lower ADC values (rather appears bright) than the normal parotid glands and lymph nodes
Figure 3 (A-D): Contrast enhanced T1 weighted images. (A) Mild enhancement of the subcutaneous lesion
(thin white arrow) at 4 min after contrast injection. (B) Image at the same level 20 min after contrast
injection shows increased enhancement within the subcutaneous lesion. (C) Moderate
homogenous enhancement of the enlarged lymph nodes at 4 min after contrast injection.
(D) At 20 min postcontrast injection, the enlarged lymph nodes show reduced and heterogeneous
enhancement (progressive washout). The subcutaneous lesion shows progressive delayed
enhancement over time while the lymph nodes show progressive washout of enhancement
Discussion
The earliest description of Kimura’s disease dates back to 1948 when Kimura et al.
described it as an unusual granulation tissue associated with lymphatic hyperplasia.[1] The pathologic lesion consists of follicles comprising eosinophils, plasma cells,
lymphocytes, and mast cells with associated proliferation of vessels and fibrosis
of the stroma.[2] It usually affects Asian males in second, third, and fourth decade.[1] The most common presentation is painless, single or multiple subcutaneous nodules
in the head and neck region, most often in the parotid and submandibular location.[3] Rarely, other sites such as parapharyngeal space can also be involved.[4] The associated key features which are highly valuable in making a clinical diagnosis
is peripheral eosinophilia (10–70%) and raised serum IgE level (800–35,000 IU/mL).[3],[5] This characteristic constellation of features—mass-like inflammatory lesion in periparotid
region, peripheral eosinophilia, and raised serum IgE levels—is the basis of clinical
diagnosis of Kimura’s disease.
MRI and computed tomography (CT) are the key imaging modalities in Kimura’s disease.
Majority of the lesions in Kimura’s disease occur in proximity to parotid gland, either
within its parenchyma or within the periparotid subcutaneous space and infiltrating
into the parotid gland parenchyma.[6] In two large case series evaluating the CT and MRI features of Kimura’s disease,
two morphological patterns of the lesions were noted; that is, well-defined nodular
pattern and ill-defined infiltrative or plaque-like pattern.[7],[8] The infiltrative or plaque-like morphology was far more common than the well-defined
nodular pattern, both occurring in these studies at 84 and 98%, respectively.[7],[8] The MRI signal intensity of these lesions was variable on T1-weighted images and
predominantly hyperintense on T2-weighted images.[7],[8],[9] On contrast-enhanced CT and MRI images, the pattern of enhancement is variable in
terms of degree of enhancement and heterogeneity, owing to varying degrees of stromal
fibrosis and vascular proliferation. However, a relatively homogenous pattern and
intense or marked enhancement has been reported in majority of cases.[7],[8],[9] Some authors describe intense enhancement as a classical feature of Kimura’s disease.[6] Another interesting feature of Kimura’s lesion is the presence of serpentine signal
intensity void areas on T2 and contrast-enhanced images, as seen in our case. These
are due to prominent vascular structures in the lesion owing to pathologic vascular
proliferation.[8]
The role of DWI in Kimura’s disease has been explored in recent years.[10],[11] The differential signal intensity of the subcutaneous parotid/periparotid Kimura’s
lesion and the associated lymphadenopathy is an important characteristic feature on
DWI. There is heterogeneous and intermediately high signal intensity of the subcutaneous
Kimura’s lesion and markedly high signal intensity of the associated lymphadenopathy
on DWI. Correspondingly, the ADC values of subcutaneous parotid/periparotid lesion
are higher compared to the ADC values of the involved lymph nodes. Relative hypercellularity
of the lymph nodes is considered to be the cause of its high signal intensity on DWI.
The role of dynamic contrast-enhanced MRI in Kimura’s disease has been studied by
Horikoshi et al. in seven patients.[10] They studied the time–intensity curves of enhancement in the subcutaneous Kimura’s
lesion and the associated involved lymph nodes. They found that the subcutaneous Kimura’s
lesions showed gradual upward or progressive delayed enhancement, while the associated
lymphadenopathies showed early enhancement. The presence of fibrosis in the subcutaneous
lesion is considered to be the cause for its progressive delayed enhancement.[10] The differential imaging features of subcutaneous lesion and the associated lymphadenopathy
on dynamic contrast-enhanced MRI and DWI are characteristic and have been demonstrated
to be useful in differentiating Kimura’s disease from other commoner and more sinister
pathologies of head and neck, especially malignant lymphoma.[10],[11] Wang et al. have also investigated the role of magnetic resonance spectroscopy in characterizing
Kimura disease. They found relatively high choline/creatine ratios in the involved
lymph nodes and relatively low choline/creatine ratios in the subcutaneous lesion.[11]
Although the confirmatory diagnosis of Kimura’s disease is pathological, the differential
behavior of subcutaneous parotid/periparotid lesion and the associated lymphadenopathy
on MRI, especially DWI and contrast-enhanced MRI are of great importance in its noninvasive
diagnosis.
Informed consent
Written informed consent for medical information and images to be published in this
case report was provided by the patient.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient has given his consent for his images and other clinical information
to be reported in the journal. The patient understands that his name and initials
will not be published and due efforts will be made to conceal his identity, but anonymity
cannot be guaranteed.
