Kimura’s disease in the groin of a middle-aged woman

A 42-year-old female was referred to our hospital with an approximately ten-year-history of a slowly growing right inguinal lump. Physical examination revealed a solitary mass measuring 7×5 cm with a normal overlying skin. She had slight tenderness over the right inguinal region. Blood investigation showed peripheral eosinophilia  (49% of white blood cell count: 12,500/μL).

Computed tomography (CT) revealed a subcutaneous isodense mass with an irregular margin and regional lymphadenopathy in the right groin (Fig. 1). In magnetic resonance imaging (MRI), the signal of the mass was isointense to the muscle on T1-weighted images, and hyperintense foci corresponding to the fat and signal voids were identified in the lesion (Fig. 2). On T2-weighted images, the lesion was heterogeneous and also contained hyperintense foci and signal voids (Fig. 3). Coronal T1-weighted images showed hyperintense nodular components and irregular shaped isointense areas within the mass lesion (Fig. 4a), and the signals of the nodular components and the enlarged lymph nodes were intensely enhanced on fat-suppressed postcontrast images (Fig. 4b).

Background

Kimura’s disease (KD) is a rare, benign, chronic inflammatory disorder of unknown etiology, which was systemically analyzed by Kimura et al. in 1948 [1,2]. The lesion is characterized by consistent histologic features such as follicular hyperplasia, eosinophilic infiltrates and proliferation of postcapillary venules [3].

Clinical Perspective

Kimura’s disease typically presents as a painless subcutaneous mass in the head and neck, frequently associated with regional lymphadenopathy and/or a salivary gland involvement, but rarely involves the other anatomical sites such as the trunk and extremities [4]. It is characterized by elevated serum Immunoglobulin E (IgE) and peripheral blood eosinophilia [3].  Because the lesion is easily invasive and accompanied by enlarged lymph nodes, differentiation from acute inflammatory lesions and malignancy becomes important issue. Preoperative diagnosis is even more difficult when the lesion is located in atypical sites, as in this case. Although pathological evidence is essential for the definite diagnosis of KD,  CT and MRI images are also useful in identifying the extent of the disease and suggesting a diagnosis.

Imaging Perspective

Although the imaging findings of KD may vary or not specific, the lesions are usually presented as ill-defined infiltrative masses in the subcutaneous tissue associated with lymphadenopathy. Some previous studies have suggested that the subcutaneous mass in KD is identified as a hypervascular lesion with signal voids and homogenous enhancement after gadolinium injection [5,6]. An additional feature is the presence of irregular and thick strands of hyperintense signals corresponding to fatty tissue within the lesion, which implies an infiltrative nature of the inflammatory disorder [7]. When a subcutaneous lesion with these findings of flow voids, fat component (T1 hyperintense), and lymphadenopathy is encountered, elevated eosinophils and IgE should be confirmed. The final diagnosis is made by pathological evidence.

Outcome

Although a standard therapy of KD has not yet been established, treatment options of the disease include surgical resection, regional or systemic steroid therapy, immunosuppressive agents (e.g., cyclosporine, omalizumab, or imatinib), cytotoxic therapy and radiation [4,8,9]. In our case, the patient had a good clinical response with corticosteroid therapy and her inguinal mass and regional lymph nodes reduced in size and signal intensity on T2-weighted image. It is assumed that the anti-inflammatory effect reduced the infiltration of lymphocytes and eosinophils and induced fibrosis of the stroma. An excision was performed after corticosteroid therapy, and the diagnosis was pathologically confirmed.

Take Home Message / Teaching Points

When cases of ill-defined subcutaneous mass with flow voids, fat component (T1 hyperintense), and lymphadenopathy are encountered, Kimura's disease should be taken into consideration.

Final Diagnosis

Kimura’s disease

Skin biopsy was performed to obtain critical information on the diagnosis. Histologically, the lesion located subcutaneously was made up by multiple well-defined or enlarged lymphoid follicles with prominent germinal centers surrounded by hypercellular interfollicular areas containing many eosinophils and postcapillary venules (Fig. 5a & b). The germinal centers also contained eosinophils, and a granulomatous area with eosinophilic necrosis was present. Immunohistochemically, a reticular staining pattern of IgE deposition was seen in the germinal centers (Fig. 5c).

All patient data have been completely anonymized throughout the entire manuscript and related files.