Axillary artery engulfed by Kimura disease mimicking a peripheral neurilemoma: a case description

Introduction

Kimura disease (KD), also called eosinophilic lymphogranulomatosis, is a rare, benign, and chronic lymphoproliferative disorder with unknown etiology. Recent research has reported a potential link between human polyomavirus type 6 and the development of KD (1). The disorder was first described by Kim and Szeto in Chinese literature in 1937 (2). This condition progresses slowly, accompanied by painless subcutaneous masses and lymphadenopathy. KD predominantly affects Asian adult men in the second to third decade of life (3). KD patients often exhibit increased levels of peripheral blood eosinophilia and serum immunoglobulin E (IgE) (2). The head and neck region is the most prevalent location for KD manifestations. While KD primarily affects adults, it can also present in children as soft-tissue masses in the subcutaneous fat layer of the humerus epitrochlear region. These masses are associated with lymphadenopathy and lymphatic drainage (4). Additionally, cases of axillary enlargement and soft-tissue masses or lymphadenopathy across multiple other body parts have been reported. In some instances, KD has appeared as enlarged axillary lymph nodes (5), inguinal lymphadenopathy (6,7), and an asymptomatic solitary brown-pigmented nodule on the left buttock skin (8).

To date, no reports of KD affecting rare locations, including the axillary neurovascular bundles zone, appear to have been reported. This article reports the case of a patient with a shuttle-shaped solid mass with well-defined walls, engulfing the axillary artery, and lesions with abundant blood flow signals. The mass was accompanied by lymphadenopathy in the supraclavicular fossa. On initial magnetic resonance imaging (MRI) and plain computed tomography (CT) scans, the presentation was suggestive of peripheral neurilemoma due to its resemblance to features such as fascicular, target, and tail signs, and fat fractionation (9). However, post-contrast injection imaging may reveal hyperintense blood flow in the axillary artery distinct from any adjacent nerves. Thus, further investigation was required into this atypical lymphadenopathy of unknown etiology.

Case presentation

The current report describes a rare case of KD in a 29-year-old female admitted to The Eighth Affiliated Hospital, Sun Yat-sen University to evaluate a painless, solid, and mobile right axilla tumor. Preoperative blood tests indicated an elevated absolute eosinophil count [0.70×10⁹/L; normal range, (0.02–0.52)×10⁹/L] and percentage (9.0%; normal range, 0.4–8.0%). However, all other laboratory parameters were within normal limits. The skin examination revealed no abnormalities, allergic reaction signs, or infections. The neurological examination was unremarkable.

The ultrasound results (Figure 1A,1B) showed a solid lesion located superficially to the muscles in the left axilla. It was approximately 33 mm × 19 mm × 25 mm in size, oval-shaped, with clear boundaries and a visible capsule. Doppler ultrasound (Figure 1B) revealed abundant blood flow signals in the lesion. The mass encircled the axillary artery, compressed the axillary vein, had a clear boundary with the surrounding nerves, and had no acoustic shadow behind it.

Figure 1 The ultrasound screening for axillary masses. (A) Ultrasound showing a solid oval-shaped mass beneath the superficial muscle layer in the left axilla. The surrounding muscles were pushed and compressed, and there was no acoustic shadow behind the mass. (B) Color Doppler ultrasound showing that the mass was rich in internal blood flow, encircled the axillary artery, and compressed the axillary vein, and had a clear boundary with the surrounding nerves.

MRI revealed a fusiform soft-tissue mass in the subcutaneous fat axilla layer adjacent to the short biceps brachii head, measuring approximately 33 mm × 19 mm × 35 mm. The mass exhibited a “tail sign” (as indicated by the red arrows in Figure 2), indicating a neurovascular bundle connection. On T1-weighted imaging (T1WI), the mass showed iso-signal intensity, appearing to merge with the adjacent muscle (Figure 2C). However, the T2-weighted imaging (T2W1) fat-suppressed sequence revealed that the mass had high signal intensity compared to the surrounding muscle (Figure 2G). The axial T2WI fat-suppressed sequence (Figure 2B) revealed central hypointensity and peripheral hyperintensity consistent with the “target sign”. Dot-like or tubular signal voids represented neovascularization, and multiple thin hypointense rings around the axillary artery were observed on the T2WI fat-suppressed sequence, resembling a “fascicular sign” (as indicated by the yellow arrow in Figure 2G). The mass showed high signals on diffusion-weighted imaging (DWI) and low intensity on apparent dispersion coefficient (ADC) mapping (Figure 2J). No significant signal changes or surrounding edema were observed in the short biceps brachii head or subcutaneous fat layer (Figure 2E). Gadolinium-enhanced T1WI showed heterogeneous mass enhancement. The supraclavicular fossa and axilla lymphadenopathy showed a bright high DWI signal with a lower signal on ADC mapping (as indicated by the cyan triangles in Figure 3).

Figure 2 The MRI images showed a fusiform soft-tissue mass situated in the subcutaneous fat layer of the axilla. The mass was adjacent to the biceps brachii short head. No definite signal changes or surrounding edema were observed in the biceps brachii, short head, and subcutaneous fat layer. An isosignal was observed on T1WI (C), a slightly high signal on T2WI (A), a slightly high signal on fat-suppressed T1WI (D), and a high signal on fat-suppressed T2WI (B). Focal low-signal shadows were observed in the central area inside the mass (blue arrow), presenting a “target sign”. (G) Additionally, dot-like or tubular signal voids highlighting the axillary artery and neovascularization, surrounded by circular low-signal bands, were observed on coronal fat-suppressed T2WI, imitating a fascicular sign (as indicated by the yellow arrow). (F-H) The mass exhibited a confusing tail sign (red arrows), and appeared to connect with neurovascular bundles. The boundary between the mass and the adjacent muscles was clear on the coronal T2WI scans, and a thin layer of fat space was observed (as indicated by the green arrow), which presented as the “split-fat sign”. The axillary nerve adjacent to the mass appeared to be compressed (as indicated by the white arrow). (I) The lesion showed an obvious high signal on DWI mapping, and a focal low-signal in the central area (as indicated by the blue arrow), corresponding to the position of the “tail sign”. (J) The lesion showed an obvious low signal on ADC mapping. (E,H) Gadolinium-enhanced T1WI showed the homogeneous enhancement of the mass, while the focal low-signal area in the central area showed the flow-void effect of blood vessels. ADC, apparent dispersion coefficient; CE, contrast-enhanced; DWI, diffusion-weighted imaging; MRI, magnetic resonance imaging; T1WI-fs, T1-weighted imaging fat-suppression; T2WI-fs, T2-weighted imaging fat-suppression.

Figure 3 The MRI imaging of enlarged lymph nodes in the supraclavicular fossa and axilla. (A,B) The supraclavicular fossa and axilla lymphadenopathy demonstrated a slightly higher signal intensity than muscle on the fat-suppressed T2WI images. (C,F) Obvious enhancement was observed on the fat-suppressed T1WI images. (D,E) The supraclavicular fossa and axilla lymphadenopathy appeared as bright, high signals on DWI with lower signal intensity on ADC. The blue triangular symbols in the images mark the enlarged lymph nodes in the supraclavicular fossa and axilla. ADC, apparent dispersion coefficient; CE, contrast-enhanced; DWI, diffusion-weighted imaging; MRI, magnetic resonance imaging; T1WI-fs, T1-weighted imaging fat-suppression; T2WI-fs, T2-weighted imaging fat-suppression.

The CT-enhanced scan showed mild to moderate improvement because of the delayed wash-in and slow wash-out of iohexol in the mass. Conversely, the arterial phase CT-enhanced multiplanar reconstruction showed an irregular lumen in the mass near the axillary artery wall (Figure 4).

Figure 4 The CT images of the axillary mass. Plain (A,B), artery phase axial (C), and vein phase axial (D) CT images of the KD mass. An oval isodense mass was observed beneath the left axilla. It had clear margins, and the adjacent muscles were compressed and displaced. (E) Artery phase MPR image depicting encasement of the axillary artery (as indicated by the white arrow). CT, computed tomography; KD, Kimura disease; MPR, multiplanar reconstruction.

The surgical findings revealed that the mass had engulfed and adhered to the axillary artery while compressing the adjacent axillary nerve. Complete axillary artery dissection was not feasible because of the adhesion (Figure 5A,5B). The pathological evaluation supported a diagnosis of KD, called eosinophilic hyperplastic lymphogranuloma (Figure 6A-6F). The post-surgical IgE level evaluation by electrochemiluminescence revealed a significant elevation of up to 3,272.00 IU/mL, exceeding normal adult levels (<100 IU/mL). Before discharge, the percentage (0.52%) and absolute value of peripheral eosinophilia had decreased, reaching average levels.

Figure 5 The KD mass in the left axilla had a smooth surface (A,B). The cut surface was grayish-yellow, solid, and of medium texture. The axillary artery was observed to be encircled by the mass during the operation. KD, Kimura disease.

Figure 6 The histological follicular structure proliferation, infiltrated by eosinophils, plasma cells, lymphocytes, and mast cells, demonstrated related vascular proliferation along with stromal fibrosis. (A) HE staining ×10 lymphocyte proliferation with lymphoid tissue hyperplasia and follicular lysis (as indicated by the arrow). (B) HE ×40 hyper-endothelial venules (as indicated by the black triangles) were observed in the germinal center. (C) HE staining ×40 hyper-endothelial venules (as indicated by the black triangles) were observed in the interfollicular zone. (D) HE staining ×100 lymphocytosis showed diffuse eosinophils, plasma cell infiltration, eosinophilic microabscesses, and interfibrillar substance. (E) Immunohistochemistry revealed that the tumor cells were positive for CD34 expression under ×40 magnification. (F) Immunohistochemistry revealed that the tumor cells were positive for CD31 expression under ×40 magnification. CD, cluster of differentiation; HE, hematoxylin-eosin.

The patient refused steroidal anti-inflammatory medication or local radiation therapy. A 6-month postoperative MRI revealed no signs of recurrence, significantly decreased lymph node enlargement, normal peripheral eosinophilia levels, and no additional complications.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

Irrespective of the treatment strategy, KD is a rare and benign chronic lymphoproliferative disorder with a favorable prognosis. Documented treatments include surgical excision, radiation therapy, and medication such as steroids and immunomodulatory agents, used singly or in combination. Surgical intervention is preferred for localized lesions. However, the recurrence rate after such interventions remains high at around 60% (5). Although recurrence does not indicate malignant potential, active combination therapies have been shown to effectively reduce the risk of recurrence (10).

The typical manifestations of KD include subcutaneous nodules and regional lymphadenopathy along the lymphatic drainage. These are commonly observed in the head and neck region and, less frequently, across the upper arms (11). Additionally, systemic involvement, including kidney damage, has been observed (12). In summary, KD has a wide range of presentations. However, non-invasive diagnosis is challenging due to variable imaging findings, which can result in the misdiagnoses of other soft-tissue masses. This could lead to potentially harmful invasive diagnostic procedures or needless radical surgery.

A previous study (13) have categorized subcutaneous masses into two morphological patterns. Type 1 masses are well-defined and nodular without liquefaction necrosis. They exhibit uniform enhancement while maintaining clear separation from the adjacent subcutaneous fat space. Conversely, Type 2 masses are ill-defined, plaque-like, and larger without necrosis. They generally exhibit mild-to-moderate heterogeneous enhancement. Higher-density soft-tissue nodules with blurred adjacent subcutaneous fat space accompany Type 2 masses. A third category, Type 3 masses, combines the characteristics of Types 1 and 2, while representing various inflammatory stages. KD is a self-limited condition that manifests as different inflammation stages, classified into these three types. The mass described in this case report aligns with Type 1, indicating an early disease stage without invasion in the subcutaneous fat layer or fibrosis. No liquefaction necrosis or calcification signs were detected throughout the course of the disease.

Variable imaging findings have been reported for KD masses, such as hyper density on CT scans, and variable signal intensities on MRI scans. The imaging findings ranged from homogeneous to heterogeneous post-contrast. The KD mass reported in this study demonstrated iso-intensity on the T1WI MRI images and slight hyperintensity on the T2WI images with homogeneous enhancement. Notably, the enhancement level was lower on the CT scans than the MRI scans, suggesting a pattern of delayed wash-in and slow wash-out. This discrepancy could be due to the image acquisition timing. The post-contrast CT scans were acquired after injecting the contrast. Conversely, the post-contrast MRI images required a longer acquisition time; this finding aligns with the existing literature (14).

KD demonstrates varying degrees of vascularity and fibrosis components at the histological level. Flow voids in masses were sometimes observed, suggesting early-phase lesion hypervascularity. However, in both our case and previous reports, besides neo-angiogenesis, the mass encased normal blood vessels and nerve tracts without invasion. In this study, the axillary artery was surrounded by the mass. Song et al. (4) reported a case of KD affecting the peripheral nerves in a child’s arm. Arul et al. (15) described a case with generalized lymphadenopathy in which the KD mass engulfed the brachial vessel. Lam et al. (16) described an unusual KD site characterized by three masses; one of the masses enveloped the patent cephalic vein in front of the biceps muscle, while another lesion was observed medially on the right distal arm, engulfing the basilic vein. Choi et al. (17) also described a case in which a mass surrounded a vessel. Fibrosis gradually transformed into vitrification as the disease progressed. Neoangiogenesis also progressively degenerated while the encased normal blood vessels remained patent. This distinguishing feature can be used to differentiate it from neoplastic lesions.

Normal blood vessel encasement has been observed in vascular and inflammatory disorder angiolymphoid hyperplasia with eosinophilia (ALHE) (18) but is infrequent in lymphadenopathy. In terms of histopathology, ALHE is characterized by vascular proliferation with plump, cobblestone-like endothelial cells, surrounded by a cellular infiltrate of lymphocytes, plasma cells. Lymphoid follicles are rarely seen. Conversely, KD is characterized by lymphoid nodules with germinal centers, extending from the dermis to the underlying fascia and muscle, and a systemic eosinophilic infiltrate and microabscesses (15). The KD reported in the study was located in the neurovascular axilla region, and a peripheral nerve sheath tumor was the primary differential diagnosis.

Kumar et al. (19) reported a case of a 69-year-old woman presenting with radiating neurological symptoms in the left upper extremity, including a tingling sensation in all fingertips, pain, and swelling in the left armpit, suggestive of a neurological disorder. A rare schwannoma was found in the axillary nerve. However, in most cases, lesions typically present in the head, neck, and flexor aspect of the limbs. Distinguishing between these lesions on MRI based on signal intensity, the enhancement pattern, or the nerve relationship is challenging because of their similarity. The nerve apposition sign, indicating eccentric nerve fiber displacement, is the key feature that can lead to a misdiagnosis of schwannoma. The primary features used to differentiate between diagnosis is the presence or absence of embedded blood vessels and lymphadenopathy. The age of onset and accompanying symptoms vary between the lesions. In this case, no muscle denervation changes, such as denervation edema, atrophy, or fatty degeneration of dependent muscle groups, were observed. The spilt-fat sign, tail sign, and fascicular sign were highly similar to the imaging manifestations of peripheral nerve sheath tumors; however, on contrast-enhanced imaging, it appeared that the low-signal area in the central region of the target sign was not the encased nerve, but the axillary artery.

Laboratory examinations indicate that increased IgE is likely associated with allergic reactions. Interestingly, due to the presence of eosinophilia and increased IgE levels, KD is thought to be an allergic-related condition. Conversely, no such direct correlation has been found between increased IgE levels and schwannoma (11). The reported KD had to be differentiated from axillary and supraclavicular enlargement lymph nodes induced by benign reactive nodes, sarcoidosis, breast cancer lymph node metastasis, tuberculosis, and lymphoma. First, the mass was differentiated from a lymph node based on the blood flow characteristics. The medical history and physical examination showed that the lesion was unilateral and painless. The patient had no history of cancer, and no palpable breast mass was observed. Thus, breast cancer lymph node metastasis, benign reactive nodes, and sarcoidosis were essentially ruled out. Lymphadenopathy associated with tuberculosis often appears with fever and ring-like lymph node enhancement accompanied by central necrosis. Cavanna et al. (20) reported the case of a 66-year-old man with right axillary lymphadenopathy, which developed approximately 10 days after receiving the third BNT162b2 vaccine dose. The histological examination indicated an anaplastic lymphoma kinase (ALK) negative, but recombinant cluster of differentiation (CD) 30-positive anaplastic large cell lymphoma. The patients reported pain in the previously mentioned cases. However, lymphoma often presents as painless lymphadenopathy, rendering it challenging to differentiate axillary KD from lymphoma through imaging and clinical symptoms (21). Therefore, a pathological biopsy is the most effective method for differentiating between KD and lymphoma.

Conclusions

We presented a rare case of a KD mass encasing the axillary artery that mimicked a peripheral neurilemoma. This report seeks to raise awareness of an unusual manifestation of KD. Due to the diverse locations and imaging manifestations of KD, ruling out other possible diseases before its diagnosis is crucial.

Acknowledgments

None.

Footnote

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-1962/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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