Surg Today (2004) 34:950–953DOI 10.1007/s00595-004-2813-6

Case Reports

Mediastinal Neurofibroma Originating from the Left IntrathoracicPhrenic Nerve: Report of a Case

Hajime Saito, Yoshihiro Minamiya, Kasumi Tozawa, Ikuo Matsuzaki, Kosei Taguchi, Taku Nakagawa,and Jun-ichi Ogawa

Department of Surgery, Division of Thoracic Surgery, Akita University School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan

routine chest X-ray. Her family and medical history wasunremarkable and she denied any history of smokingor alcohol. Physical examination was unremarkable,and the results of baseline laboratory tests were normal.Chest X-ray showed a smooth, round shadow in theleft middle lung field adjacent to the heart (Fig. 1).A computed tomography (CT) scan demonstrated thisshadow as a homogeneous solid mass in the middlemediastinum (Fig. 2a). T2-weighted axial magneticresonance (MR) imaging showed higher signal intensityin the peripheral mass lesion than in the central zone(Fig. 2b).

We performed video-assisted thoracic surgery(VATS) with a double-lumen endotracheal tube forsingle lung ventilation, while the patient was undergeneral anesthesia. After placing the patient in the rightlateral decubitus position, we inserted a trocar throughthe midaxillary line of the seventh intercostals space.General exploratory thoracoscopy revealed a well-circumscribed 25-mm tumor in the middle mediastinum,traversed by the left phrenic nerve (Fig. 3). We made anadditional intercostal incision through the anterior lineand simultaneously resected the phrenic nerve, whichwas involved by tumor (Fig. 4a).

Microscopically, the tumor was composed of cellswith long, narrow nuclei, and wavy bands of spindle-shaped cells with myxomatous interstitial tissue in thebackground (Fig. 4b). The histopathological diagnosiswas neurofibroma originating from the left phrenicnerve in a patient with no clinical evidence of vonRecklinghausen’s disease. Postoperatively, the patienthad left phrenic nerve paralysis, but without clinicalsymptomatology. Furthermore, spirometry done 6months after the operation showed minimal change,with a forced vital capacity of 3.89 l (4.0 l before surgery)and a forced expiratory volume in 1 s of 2.98 l (3.14 lbefore surgery).

AbstractWe report a case of mediastinal neurofibroma originat-ing from the left phrenic nerve in a 42-year-old womanwho was referred to us after a routine chest X-rayshowed a smooth, round abnormal shadow in the leftmiddle lung field adjacent to the heart. We resected a 25� 20 � 20-mm tumor by video-assisted thoracic sur-gery. Histopathological examination confirmed that thelesion was a mediastinal neurofibroma originating fromthe left phrenic nerve without von Recklinghausen’sdisease. Neurogenic mediastinal tumors originatingfrom the phrenic nerve are very rare, and to the best ofour knowledge, no other case of a mediastinal neurofi-broma originating from the phrenic nerve in a patientwithout von Recklinghausen’s disease has ever beenreported.

Key words Neurofibroma · Mediastinal tumor · Phrenicnerve

Introduction

Neurogenic tumors of the mediastinum account for20%–30% of all mediastinal tumors;1,2 however, tumorsoriginating from the intrathoracic phrenic nerve, espe-cially neurofibroma, are rare. We report what to ourknowledge is the first documented case of a mediastinalneurofibroma originating from the phrenic nerve in apatient without von Recklinghausen’s disease.

Case Report

A 42-year-old woman was referred to us for evaluationof an abnormal shadow in the left middle lung field on a

Reprint requests to: H. SaitoReceived: March 3, 2003 / Accepted: January 20, 2004

951H. Saito et al.: Neurofibroma of the Phrenic Nerve

Fig. 1. Chest X-ray film showed a smooth, round shadow inthe left middle lung field, adjacent to the heart

Discussion

About 20%–30% of all mediastinal tumors are neuro-genic in origin,1,2 the most common being schwannoma(57.5%) and neurofibroma (18.9%),1,3 which usuallydevelop in the posterior part of the mediastinum(96.7%), and originate from the intercostal or sympa-thetic nerve, and occasionally from the vagus nerve.3

Our research of the literature found a total of 62 casesof intrathoracic vagal nerve tumors, 52 of which wereschwannoma and 10, neurofibroma.4 Conversely, only15 cases of tumors of the intrathoracic phrenic nervehave been reported, all of which were schwannoma.5

Although sporadic reports of mediastinal schwannomaoriginating from the phrenic nerve6 and neurofibromawith von Recklinghausen’s disease exist,7 we could not

find any other reports of mediastinal neurofibromaoriginating from the phrenic nerve in a patient withoutvon Recklinghausen’s disease.

Histologically, neurofibroma consists of a prolifera-tion of thick wavy collagen bundles with varying de-grees of myxoid degeneration. Schwannoma are dividedhistologically into two types, Antoni type A, which con-sists of tightly packed nerve sheath cells, and Antonitype B, which consists of scattered tumor cells withinmyxoid matrices. Sakai et al. found that MR findingscorrelated will with the pathological findings of in-trathoracic neurogenic tumors.8 An inhomogeneouslyhigh-intensity appearance on T2-weighted images cor-responds to alternating Antoni A and B areas in theschwannoma. Moreover, high-intensity regions in theperiphery of a neurofibroma on T2-weighted images

Fig. 2a,b. Enhanced computed to-mography scan showed a non-enhanced mass in the left middlemediastinum. a The mass was sharplymarginated and proved to be homo-geneous and solid. b T2-weightedaxial magnetic resonance imagedemonstrated a higher signal inten-sity in the peripheral mass than thatin the central zone

Fig. 3. Intraoperative findings of the neurogenic tumor origi-nating from the left phrenic nerve. A well-circumscribed25-mm tumor was identified in the middle mediastinum andwas traversed by the left phrenic nerve

952 H. Saito et al.: Neurofibroma of the Phrenic Nerve

correspond to myxoid degeneration, whereas nodularareas of low signal intensity correspond to collagenousfibrous tissue. Varma et al. reported that this targetsign on T2-weighted MR images was seen in 52% ofcases, and proved helpful in differentiating neurofi-broma from malignant peripheral nerve sheath tumors.9

In the present case, the T2-weighted axial MR imagedemonstrated a higher signal intensity in the peripheralmass than in the central zone. On the cut surface ofthe gross specimen, the peripheral zone appeared to begelatinous, whereas the central zone appeared to besolid. This finding is consistent with the report ofSakai et al., and may prove useful for the preoperativediagnosis.

Malignant degeneration occurs in 10% of neurofibro-mas3 and considering this fact, transection of the nervemight be indicated for certain patients.10,11 It may bepossible to preserve the nerve during excision ofschwannoma, because schwannomas are encapsulatedlesions of nerve sheath origin, which grow from theformation of a lateral mass on the parent nerve, oftenmaking the nerve easily identifiable. Conversely, neuro-fibromas are non-encapsulated, they possess a poorlyorganized structure, and they grow by diffusely expand-ing the parent nerve containing all nerve elements, in-cluding axons, sheath cells, and connective tissue, whichmay prevent the axons from being identified as theycourse through the tumor.2 Therefore, to completelyexcise the neurofibroma, nerve preservation is oftenimpossible. Unilateral phrenic nerve paralysis usuallyresults in minimal morbidity, but it may be symptomaticwith borderline lung function, in which case, diaphrag-matic plication seems effective. On the other hand,

Schoeller et al. reported that immediate microsurgicalreconstruction of the phrenic nerve with a nerve graft,which is less invasive, could be effective for symptom-atic hemidiaphragmatic paralysis.12 However, they rec-ommended this procedure only if there was an adequatetime frame to allow complete reinnervation, consider-ing that a nerve regenerates at a velocity of 1 mm perday from the proximal nerve to the diaphragm, and ifthe patient’s general condition enabled the extra oper-ating time needed for reconstruction without increasingthe risk. Therefore, in selected patients, reconstructionof the phrenic nerve is an excellent method of reanimat-ing the diaphragm. Because the ultimate goal of surgeryis to achieve safe and complete tumor excision, we sug-gest considering the nerve anastomosis to prevent com-plete phrenic nerve palsy.

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Fig. 4a,b. Cut surface of the gross specimen revealed that theperipheral zone had a gelatinous appearance and the centralzone had a solid appearance. a The phrenic nerve was com-pletely involved (bar � 10 mm). b Histological examination

revealed long and narrow nuclei, and wavy bands of spindle-shaped cells with myxomatous interstitial tissue in the back-ground (H&E, �400)

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