Sung Eun Song, MD, PhD,1 Bo Kyoung Seo, MD, PhD,1 Jung-Woo Choi, MD, PhD, ... Ansan-city, Kyunggi-do, Korea ... brachial plexus can develop in the axilla.
Case Report
The Sonographic “Coffee Bean” Sign Helps Distinguish an Axillary Neurofibroma From a Lymphadenopathy Sung Eun Song, MD, PhD,1 Bo Kyoung Seo, MD, PhD,1 Jung-Woo Choi, MD, PhD,2 Gil-Soo Son, MD, PhD,3 Kyu Ran Cho, MD, PhD,4 Baek Hyun Kim, MD, PhD1 1
Department of Radiology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan-city, Kyunggi-do, Korea 2 Department of Pathology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan-city, Kyunggi-do, Korea 3 Department of General Surgery, Korea University Ansan Hospital, Korea University College of Medicine, Ansan-city, Kyunggi-do, Korea 4 Department of Radiology, Korea University Anam Hospital, Korea University College of Medicine, Seoul, Korea Received 27 August 2012; accepted 28 February 2013
ABSTRACT: Axillary masses may represent various soft tissue tumors or lymphadenopathy. Neurofibromas are benign peripheral nerve sheath tumors and, while they are very uncommon, it is important to remember that neurogenic tumors arising from brachial plexus can develop in the axilla. We describe an axillary neurofibroma arising from the brachial plexus that presented with a “coffee bean sign” on sonography that distinguished it from axillary lymphC 2013 Wiley Periodicals, Inc. J Clin adenopathy. V Ultrasound 42:33–37, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ jcu.22051 Keywords: neurofibroma; axilla; ultrasonography; brachial plexus; peripheral nerves; neoplasms
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he axilla contains various mesenchymal tissues, such as fat, vasculature, lymphatics, and nerves, that give rise to various diseases. Breast diseases are commonly found in the axilla because of the presence of accessory breast tissues. The most common palpable axillary masses are lymph node metastases from breast cancer. Neurogenic tumors, such as schwannomas or neurofibromas, can develop in the axilla from the brachial plexus. Although neurofibromas are reported to arise throughout Correspondence to: B. K. Seo C 2013 Wiley Periodicals, Inc. V
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the body, neurofibromas arising from the brachial plexus are very uncommon in axilla,1 and therefore, the possibility of a neurofibroma in the axilla is sometimes overlooked. We report an axillary neurofibroma arising from the brachial plexus that has a “coffee bean sign” on ultrasound (US) that distinguished it from axillary lymphadenopathy.
CASE REPORT
A 50-year-old woman presented with a palpable mass in her right axilla. The mass was nontender; however, she complained of pain radiating down her right arm while a physician was examining the mass. US examination performed with a 6–15 MHz linear transducer (LOGIQ 9 unit; GE Medical Systems, Milwaukee, WI) revealed a well-circumscribed, oval-shaped, heterogeneous echoic mass measuring approximately 4.9 cm in the right axilla. The mass had a thin echogenic rim. The mass demonstrated a prominent band-like hyperechoic central region, with a hypoechoic periphery (Figure 1A). Color Doppler images revealed central vascularity within the mass, similar to the hilar blood flow of a lymph node (Figure 1B). According to the physician’s request to obtain an exact pathologic diagnosis, an US-guided core needle biopsy was performed using a 14-gauge needle and an 33
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FIGURE 2. Post-contrast-enhanced chest CT scan shows a welldefined, oval-shaped mass with minimal homogeneous enhancement (arrows) in the right axilla.
FIGURE 1. Transverse images on US reveal a circumscribed, ovalshaped, heterogeneous echoic mass (arrows) measuring approximately 4.9 cm in the right axilla. A coffee bean sign with a central echogenic band (arrowheads) and a hypoechoic peripheral zone are seen within the mass (A). Color Doppler US shows central vascularity within this mass that is suggestive of feeding axillary vessel (B).
automated biopsy device (Bard-Magnum Biopsy Instrument; CR Bard, Covington, GA). Three months after the biopsy, CT and MRI were performed to evaluate the mass further. A 64-channel multidetector CT scan (Brilliance 64; Philips Healthcare, Andover, MA) and a 3 T MRI unit (MAGNETOM Skyra 3.0 T; Siemens Medical Solutions, Malvern, PA) were used. Chest CT scan was performed with both preand postcontrast enhancement. Pre-contrastenhanced CT scan showed a circumscribed, oval-shaped, homogeneous, isodense mass in the right axilla. There was no fat or calcification within the mass. On post-contrast CT scan, the mass exhibited minimal homogeneous enhancement (Figure 2). The mass was measured at 6 HU on pre-contrast-enhanced CT scan and 22 HU on post-contrast-enhanced CT scan. MRI 34
revealed a well-defined oval mass with homogeneous low signal intensity on precontrast T1weighted imaging and heterogeneous enhancement on post-contrast T1-weighted imaging with fat saturation. On post-contrast imaging, the central portion of the mass had band-like enhancement. A coronal fat-saturated T2weighted image showed that the mass was of heterogeneous high signal intensity accompanied by central hypointense lines (Figure 3). Schwannomas or neurofibromas are common benign peripheral neurogenic tumors. Based on the US and MRI images, the central portion of the mass demonstrated band-like hyperechogenicity on US, band-like central enhancement on post-contrast T1-weighted images, and hypointense lines on T2-weighted images. These changes in the central portion of the mass might be related to the nerve passing through the center of the mass and to fibrous collagenous tissue. Knowing this, we preferred a diagnosis of neurofibroma after reviewing the images. Surgical excision was performed and the mass was carefully dissected off the brachial plexus. During surgery, venous bleeding occurred because the axillary vein was superiorly located and small branches entered the mass (Figure 4). On histopathologic examination of the resected specimen, a proliferation of spindle cells showing markedly elongated nuclei and a wavy, serpentine configuration and pointed ends was observed (Figure 5A). This JOURNAL OF CLINICAL ULTRASOUND
SONOGRAPHIC COFFEE BEAN SIGN IN AXILLARY NEUROFIBROMA
FIGURE 3. On a coronal fat-saturated T2-weighted image, a well-defined oval mass has heterogeneous high signal intensity with central hypointense lines (arrowheads).
confirmed the diagnosis of neurofibroma arising from the brachial plexus. The mass was positive for S-100 protein and CD 34 and negative for SMA on immunohistochemical staining (Figure 5B).
DISCUSSION
Neurogenic tumors arising from the brachial plexus have been described in the neck, supraclavicular, and axillary regions.2 Primary neurogenic tumors of the brachial plexus include neurofibromas, plexiform neurofibromas, schwannomas, and malignant peripheral nerve sheath tumors.3 Although neurofibromas are the most common neural tumor to involve the brachial plexus,3 there are only rare reports of neurofibromas presenting as an axillary mass.4 Neurofibromas are benign, heterogeneous tumors that arise from the Schwann cells and fibroblasts of peripheral nerve sheaths.4 Onethird of neurofibromas occur in patients with neurofibromatosis type 1, whereas two-thirds of cases are sporadic. They can be either superficial or deep, involving small cutaneous nerves or large major nerve trunks. Superficial neurofibromas typically present as small and painless masses, whereas deeper lesions are commonly associated with neurologic symptoms.5 It is important to surgeons to be able to differentiate neurofibromas from schwannomas because neurofibromas infiltrate the nerve VOL. 42, NO.1, JANUARY 2014
FIGURE 4. Intraoperative photographs of the axillary dissection shows the neurofibroma with brachial plexus entering centrally (arrows) and an axillary vein located superior to the mass (arrowhead).
fascicle and complete resection of the tumor may consequently result in permanent nerve damage and require subsequent nerve grafting to preserve and restore function.6 Conversely, schwannomas can be easily dissected away while preserving nerve integrity.7 Unfortunately, imaging features of solitary neurofibromas and schwannomas are often overlapped and indistinguishable. On US, for example, both tumors are well-demarcated, oval-shaped, hypoechoic lesions that may or may not exhibit posterior enhancement.8 On CT imaging, both neurofibromas and schwannomas demonstrate attenuation similar to that of muscle and both also show variable amounts of enhancement. Both have an isointense signal on T1-weighted imaging and hyperintense signal on T2weighted imaging on MRI. They may have also a central area with low signal intensity, the socalled target sign on MRI. The split-fat sign represents a rim of fat surrounding the tumor, which originates from the nerve in an intermuscular location.5 The split-fat sign and target sign can be seen in both tumor lesions and are not helpful in differentiating the two.5 Differentiation between schwannomas and neurofibromas is possible if one assesses the relationship of the lesion to the nerve origin.9 Neurofibromas are not encapsulated and have a nerve entering and exiting centrally. In contrast, schwannomas are encapsulated and tend to displace the surrounding neural structures 35
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FIGURE 5. (A) Histopathologic examination demonstrates a neurofibroma formed by a proliferation of spindle cells with their markedly elongated nuclei, wavy, serpentine configuration and pointed ends (original magnification, hematoxylin-eosin stain, 340). (B) On immunohistochemical stains, the mass was positive for S-100 protein.
with the nerve entering and exiting eccentrically.10 In our case, a centrally located, bandlike echogenic lesion in the tumor on US could represent the centrally entering nerve and the central vascularity on color Doppler US may represent the neurovascular bundle. On MRI, post-contrast T1-weighted imaging revealed a central band-like enhancement with a heterogeneous background enhancement that correlated with US features. The central band-like changes on US and MRI correlate with passing nerve fascicles and collagenous tissues.11 Both central and peripheral vascularities were found to be common features in a large study of 75 peripheral nerve sheath tumors on color Doppler US with 47 of 49 schwannomas and 25 of 26 neurofibromas showing Doppler signals.7 In this case, clear central linear vascularity was seen within the mass, and therefore, the mass was 36
misinterpreted as lymphadenopathy with preserved hilar vascularity. Central vascularity in neurofibromas is rare and can be confused as an enlarging lymph node in the axilla. If a palpable mass is found in the axilla, the most likely source is a metastatic lymph node from breast cancer. The differential diagnosis for a solitary axillary mass with central vascularity on color Doppler US includes lymphadenopathy such as metastasis from carcinoma, lymphoma, or Castleman disease. If the mass contains fat or calcifications, a lipoma or harmartoma is also possible. As this case outlines, soft tissue tumors, such as schwannomas and neurofibromas, should also be considered in the diagnosis of soft tissue tumor, particularly if there is a central band-like change in the mass such as hyperechogenicity on US and high signal intensity on enhanced MRI. These findings may be caused by the passing nerve fascicles of neurofibromas and may produce a “coffee bean sign.” T2-weighted imaging can show internal linear low signal intensity that corresponds with the passing nerve. In our case, the mass engulfed the nerves and axillary vein, leading to bleeding during surgery and subsequent motor weakness in the right hand after surgery. Our hope is that in identifying the pathognomonic radiologic features of neurofibromas, we will prevent future mass excision that might result in permanent nerve damage. In conclusion, axillary masses include various soft tissue tumors and lymphadenopathy. Based on our case report, brachial pleuxus neurofibromas should be considered in the differential diagnosis of an axillary mass, in particular, if there is a coffee bean sign, which is defined as a central band-like change on US or MRI.
REFERENCES 1. Mehta D, Mehta D, Shaam M, et al. Huge axillary mass—neurofibroma brachial plexus. Indian J Surg 2011. DOI: 10.1007/s12262-011-0330-6. 2. Nakamura M, Akao S. Neurilemmoma arising in the brachial plexus in association with breast cancer: report of case. Surg Today 2000;30:1012. 3. Wittenberg KH, Adkins MC. MR imaging of nontraumatic brachial plexopathies: frequency and spectrum of findings. Radiographics 2000;20:1023. 4. Das S, Ganju A, Tiel RL, et al. Tumors of the brachial plexus. Neurosurg Focus 2007;22:E26. 5. Lin J, Martel W. Cross-sectional imaging of peripheral nerve sheath tumors: characteristic signs on CT, MR imaging, and sonography. AJR Am J Roentgenol 2001;176:75. JOURNAL OF CLINICAL ULTRASOUND
SONOGRAPHIC COFFEE BEAN SIGN IN AXILLARY NEUROFIBROMA 6. Cerofolini E, Landi A, DeSantis G, et al. MR of benign peripheral nerve sheath tumors. J Comput Assist Tomogr 1991;15:593. 7. Tsai WC, Chiou HJ, Chou YH, et al. Differentiation between schwannomas and neurofibromas in the extremities and superficial body: the role of high-resolution and color Doppler ultrasonography. J Ultrasound Med 2008; 27:161.
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8. Beggs I. Sonographic appearances of nerve tumors. J Clin Ultrasound 1999;27:363. 9. Saifuddin A. Imaging tumours of the brachial plexus. Skeletal Radiol 2003;32:375. 10. Kline DG, Hackett ER, Happel LH. Surgery for lesions of the brachial plexus. Arch Neurol 1986;43:170. 11. Fornage BD. Peripheral nerves of the extremities: Imaging with US. Radiology 1988;167:179.
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