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J Thorac Cardiovasc Surg 1998;115:240-242
© 1998 Mosby, Inc.
BRIEF COMMUNICATIONS |
Washington, D.C.
From the Departments of Pathologya and Thoracic Surgery,bGeorgetown University Medical Center, Washington D.C.
Received for publication June 3, 1997 Accepted for publication August 14, 1997. Address for reprints: Salwa Sheikh, MD, Department of Pathology,Georgetown University, 3900 Reservoir Rd., NW, Washington DC 20007.
Plexiform schwannomas are unusual benign peripheral nerve sheathtumors, and rare cases have been reported in the setting of "schwannomatosis."We are aware of only a single case having been reported in a patient withneurofibromatosis type 2 (NF-2). We present a case of multiple spinal, chestwall, esophageal, and paraesophageal plexiform schwannomas in a patient withNF-2. Emphasis is placed on correct identification of plexiform schwannoma andits distinction from plexiform neurofibroma and other tumors having a plexiformgrowth pattern.
A 37-year-old man with NF-2 was referred for treatment of hoarseness andleft vocal cord paralysis. Computed tomographic scan and magnetic resonanceimaging revealed a mediastinal mass. The patient's history was significant forbilateral acoustic schwannomas, a left parietal meningioma, multipleneurofibromas, and multiple intradural and extradural schwannomas. He underwenta right thoracotomy with resection of paraesophageal, retropharyngeal, and chestwall masses. The postoperative course was uneventful. All three specimensconsisted of irregular multinodular masses.
On histologic examination, the specimen consisted of multiple nodules oftumor, each separated by strands of nonneoplastic connective tissue (Fig. 1). Some nodules were highly cellular andcomposed of spindle cells. Characteristic cellular Antoni A areas with nuclearpalisading (Fig. 2), Verocay bodies, and short parallel fascicles of Schwanncells juxtaposed with hypocellular myxoid Antoni B regions were uniformlypresent. Neither necrosis nor hemorrhage wasseen.
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1 introduced theterm "schwannomatosis" for a syndrome characterized by multiplecutaneous schwannomas, central nervous system tumors, and various neurologicdeficits without stigmata of NF. 1In 1995 Val-Bernal, Figols, and Vasquez-Barquero 2 summarized 78 cases of plexiformschwannomas already reported in the literature; eight were associated withclinical schwannomatosis, six with multiple cutaneous schwannoma syndrome, andonly three with NF-1. They also reported, for the first time in the literature,a single case of plexiform schwannoma in a patient with NF-2. Rare cases havebeen reported in association with NF-1 schwannomatosis. In 1996, Reith andGoldblum 3 reported a case ofmultiple cutaneous plexiform schwannomas associated with bilateral acousticneuromas, as well as other intracranial and intraspinal neoplasms, 3 which may represent another exampleof plexiform schwannoma in NF-2.
Essentially, multifocal Schwann cell proliferation may be separated intothree groups 2: (1) multifocalmicroscopic schwannomatosis, (2) clinical schwannomatosis, and (3) multiplecutaneous schwannomas. Patients with multiple cutaneous schwannomas havehyperacousis associated with various intracranial tumors. Clinicalschwannomatosis is distinguished from NF-1 by its lack of skin pigmentation,neurofibromas, and autosomal dominant transmission. Multiple cutaneousschwannomas are unassociated with intracranial tumors. Some of these tumors maydevelop along the course of a large nerve segment. Like those with NF-2,patients with cutaneous schwannomas have loss of heterozygosity of chromosome22. Because the cutaneous schwannoma locus is present in the NF-2 region, thismay well represent a subtype of NF-2.
Plexiform schwannoma consists of multiple intradermal or subcutaneousnodules composed primarily of cellular Antoni A regions with nuclear palisadingand Verocay bodies. These tumors, like their more typical counterparts, arecomposed almost exclusively of Schwann cells without evidence of axons. Nomalignant transformation has been reported, although local recurrence has beenassociated with incomplete resection. Plexiform schwannoma must bedifferentiated from several other entities, including plexiform neurofibroma,plexiform fibrohistiocytic tumor, plexiform malignant peripheral nerve sheathtumor of infancy and childhood, plexiform granular cell tumor, and traumaticneuroma. Plexiform neurofibroma is a plexiform tumor composed of Schwann cells,perineural cells, fibroblasts, and axons admixed with collagen in a loosematrix. The term plexiform refers to theserpentine distortion it imparts to the affected nerve segment, which has beenlikened to a "bag of worms." It is critical to distinguish plexiformschwannoma from plexiform neurofibroma, because the latter is pathognomonic forNF-1 and carries a risk of malignant transformation, in contrast to the former.Plexiform fibrohistiocytic tumor is rare and was first described by Enzinger andZhang 5 in 1988. It usuallyarises in children or young adults, being more common in girls and young women.It is characterized by fibroblasts variably admixed with osteoclast-like giantcells. Although regional lymph node metastases have been reported, neithervisceral metastases nor tumor-related deaths have been documented. The so-calledplexiform malignant peripheral nerve sheath tumor of infancy and childhood wasdescribed in 1994 by Meis-Kindblom and Enzinger, 6 who related the findings in ninecases of a plexiform neoplasm in which there were morphologic features similarto plexiform schwannomas but which differed by having mitoses and lacking AntoniB zones. Although no lesion metastasized, the authors assumed the view thatthese were malignant neoplasms. Other authors, however, believe that the lesionsdescribed by Meis-Kindblom and Enzinger 6are instead examples of plexiform variants of cellular schwannomas, 7 benign tumors that are known to becellular, mitotically active, able to erode bone, and frequently congeners ofsarcomas.
In summary, we present a case of plexiform schwannoma in a patient withNF-2. In such a setting it is critical to distinguish the plexiform schwannomafrom plexiform neurofibroma, because the clinical and prognostic implicationsdiffer substantially for the two.
Footnotes
J Thorac Cardiovasc Surg 1998;115:240-2
References
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