Intraosseous schwannoma of tibia: Report of a rare case with review of literature

Kavita Mardi; Lekshmi Vijayamohanan; Vineet Aggarwal; Virajrao Kore

doi:10.4103/ijors.ijors_12_20

CASE REPORT

Year : 2021 | Volume : 29 | Issue : 2 | Page : 64-66

Intraosseous schwannoma of tibia: Report of a rare case with review of literature

Kavita Mardi¹, Lekshmi Vijayamohanan¹, Vineet Aggarwal², Virajrao Kore³
¹ Department of Pathology, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India
² Department of Orthopedics, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India
³ Department of Cardiology, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India

Date of Submission	18-Oct-2020
Date of Acceptance	07-Jul-2021
Date of Web Publication	20-Dec-2021

Correspondence Address:
Kavita Mardi
Set No. 14, Type VI Quarters, IAS Colony, Meheli, Shimla, Himachal Pradesh.
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/ijors.ijors_12_20

Abstract

Intraosseous schwannomas are rare and represent 0.2% of all bone tumors. Their occurrence in tibia is extremely rare and only five cases have been reported till date. We report an additional case of intraosseous schwannoma in right tibia of a 46-year-old female whose plain radiograph of right knee joint revealed an osteolytic expansile lesion with trabeculations in the proximal tibia. Magnetic resonance imaging study showed a well defined, lobulated mass in the anteromedial aspect of upper tibia. Histopathological examination of the excised specimen revealed schwannoma which was confirmed by positivity for S-100 on immunohistochemistry.

Keywords: Bone, schwannoma, tibia

How to cite this article:
Mardi K, Vijayamohanan L, Aggarwal V, Kore V. Intraosseous schwannoma of tibia: Report of a rare case with review of literature. Int J Orthop Surg 2021;29:64-6

How to cite this URL:
Mardi K, Vijayamohanan L, Aggarwal V, Kore V. Intraosseous schwannoma of tibia: Report of a rare case with review of literature. Int J Orthop Surg [serial online] 2021 [cited 2023 Mar 25];29:64-6. Available from: https://www.ijos.in/text.asp?2021/29/2/64/332928

Introduction

Schwannoma is a benign neural sheath tumor of the soft tissue, and its intraosseous presentation is very rare. It is estimated that intraosseous schwannomas represent 0.2% of all bone tumors.^{[1],[2],[3],[4],[5],[6]} The tumor may affect any site of the skeleton, including the mandible, the sacrum, vertebral bodies, the ulna, the humerus, the femur, the tibia, the patella, the scapula, the ribs, and small bones of the hand. Intraosseous schwannoma of tibia is extremely rare.^[7],[8],[9] Only five cases of intraosseous schwannoma with tibial location have been reported so far.^{[2],[7],[8],[9],[10]} We report an additional case of intraosseous schwannoma in the right tibia of a 46-year-old female.

Case Report

A 46-year-old woman presented with complaints of vague swelling and tenderness along the medial aspect of upper part of her right leg. Local examination revealed mild tenderness and fullness distal to the right knee joint without any paraesthesia or numbness. Systemic examination, including a neurological and ear, nose, and throat evaluation, was within normal limits. A plain radiograph of her right knee joint revealed an osteolytic, expansile lesion with trabeculations and a thin sclerotic margin in the proximal tibia. Magnetic resonance imaging (MRI) study showed a well-defined, lobulated mass measuring 3.2 × 1.35 cm in the anteromedial aspect of upper tibia, with thin septae and eroding the metaphyseal region of proximal tibia [Figure 1].

Figure 1: MRI revealing well-defined, lobulated mass in the anteromedial aspect of upper tibia

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She subsequently underwent a definitive tumor excision and the specimen was sent for histopathological examination. Grossly, a single fat laden 5 × 4 × 1 cm well-circumscribed mass was received, which on serial sectioning was firm in consistency and uniformly gray white in color. Microscopically, the lesion was well circumscribed and well encapsulated, comprising of alternating hypercellular (Antoni A) and hypocellular (Antoni B) areas. The hypercellular areas comprised uniform spindle cells arranged in short bundles and interlacing fascicles, with elongated, wavy/serpentine nuclei, dense nuclear chromatin, inconspicuous nucleoli, and eosinophilic cytoplasm with indistinct cytoplasmic borders. Frequent intranuclear inclusions were seen. Verocay bodies, nuclear palisading, and whorling of cells were also seen [Figure 2]. Hyalinized blood vessels were seen throughout the tumor, along with sprinkling of mast cells. S-100 positivity was noted on immunohistochemistry [Figure 3], and a diagnosis of intraosseous schwannoma of right proximal tibia was rendered. The patient did not receive any further therapy and is presently on follow-up since 8 months; she remains well and symptom-free without any recurrence to date.

Figure 2: Photomicrograph showing hypercellular (Antoni A) and hypocellular (Antoni B) areas with Verocay bodies and nuclear palisading (H&E, 20×)

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Figure 3: S-100 positivity in tumor cells (IHC, 20×)

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Discussion

Intraosseous schwannoma is a rare condition. The most widely accepted theory to justify such rarity is that these tumors appear almost exclusively in sensory fibers, which are scarce in bones, prevailing in the periosteum.^[1] In bones, these fibers are mostly located near vessels accounting for bone nutrition.^[3] Thus schwannoma can involve the bone via three main mechanisms: (1) it is extraosseous, eroding into the bone; (2) the tumor is located within the nutrient canal, with the formation of a dumbbell-shaped tumor; or (3) it arises centrally within the bone.^{[11],[12],[13]}

The most affected bone is the mandible. Although some authors believe that the long intraosseous course of the mandibular nerve results in a greater incidence of the tumor in this region, it has been reported that the same happens in other bones, with no increased incidence in these other locations. The sacrum is the second most affected site, which can be justified by the numerous sensory roots passing through its foramina, but can also occur in other bones such as humerus, ulna, metacarpals, phalanges, femur, fibula, and tibia.

Regarding the clinical presentation, these tumors may cause pain associated or not with edema. Some cases may present with pathological fracture at diagnosis. Tumor growth is slow and insidious, with long periods of evolution.^[1],[2],[3]

Radiographically, these tumors manifest as well-circumscribed lytic lesions, possibly with a sclerotic halo, which sometimes tapers or destroys the cortical layer. Adjacent soft tissues are rarely invaded. There is no calcification or bone tissue formation within the lesion.^[1],[2],[3]

Nuclear magnetic resonance is a better imaging method to assess cortical and soft tissue involvement when compared with CT. Schwannoma lesions present hypointense signal on T1-weighted images, heterogeneous signal on T2-weighted images, and diffuse paramagnetic contrast enhancement.^[3]

Important differentials on microscopy at this site include neurofibroma (unencapsulated, without characteristic Antoni A and B areas), malignant peripheral nerve sheath tumor (atypia with necrosis and atypical mitoses), benign fibrous histiocytoma (foamy cells, multinucleate giant cells, and chronic inflammation are present), and the fibrous component of fibrous dysplasia (with absence of schwannian spindle cells and negative staining for S-100).^[14] Diffuse immunoreactivity for S-100 distinguishes this tumor from other benign spindle cell lesions.

Intraosseous schwannoma is associated with a good prognosis, which is independent of its size or the presence of bone invasion.^[14] Although malignant transformation has been reported in schwannomas of soft tissues, all intraosseous schwannomas reported to date have been benign, such that curettage or marginal excision remains the therapy of choice. However, intralesional resection associated with local adjuvant therapy and bone filling also seems to be an effective method for surgical treatment.^[15],[16]

In conclusion, intraosseous schwannomas, though rare, should be kept as a clinical differential in radiographically lytic intraosseous tumors of the tibia to avoid the over treatment of patients. Furthermore, careful evaluation of family history along with a thorough neurological evaluation to rule out vestibular schwannomas or neurofibromatosis is essential in these cases.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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