Ann Thorac Surg 1999;67:1474-1476
© 1999 The Society of Thoracic Surgeons
Case Reports
Intraosseous neurilemoma of the sternum
Kohei Takata, MDa,
Kosuke Okuda, MDa,
Mitsuo Ochi, MDa
a Department of Orthopaedics, Shimane Medical University, Izumo, Japan
Accepted for publication October 12, 1998.
Address reprint requests to Dr Takata, Department of Orthopaedics, Shimane Medical University, 89-1 Enyacho, Izumoshi, Japan 693-8501
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Abstract
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Sternal benign bone tumor is uncommon. We report a very rare case of intraosseous neurilemoma in the sternum. A girl, 10 years of age, was diagnosed as having a sternal tumor. Computed tomographic scan disclosed a mushroom-shape tumor in the region from inside of the sternum to the ventral soft tissues. Surgical resection was performed. Histopathologic findings showed a typical neurilemoma with Antoni type A and B patterns. No recurrence has been found.
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Introduction
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Primary bone tumors of the chest wall are uncommon [1]. Among those tumors, sternal tumors are rare and usually malignant [2]. On the other hand, intraosseous neurilemoma is rare and accounts for less than 1% of primary bone tumors [3]. We report an extremely rare case of neurilemoma developed in the sternum.
A 10-year-old girl was referred to our department in December 1992. A tumor of 5 x 4 cm was found at the sternal region. Plain radiogram showed a round translucent focus with the surrounding sclerotic region in the manubrium of the sternum (Fig 1). Computed tomographic scan disclosed a tumor protruding from inside of the sternum to the ventral soft tissues. The cortical bone of the ventral region disappeared (Fig 2A). On T1-weighted magnetic resonance image, moderate signal intensities were found, and on T2-weighted image, high signal intensities were found. No invasion of the tumor into the thoracic cavity was found (Fig 2B). On technetium and gallium scintigram, no abnormality was observed. We presumed it was a benign tumor, and surgery was performed on January 12, 1993. A 10-cm vertical incision was made over the tumor. The tumor outside the sternum was 3.5 x 5.0 cm in size and had encapsulated with a well-defined margin. By frozen section examination of the mass, it was diagnosed as neurilemoma. The tumor outside the sternum was resected; the defect of anterior table was oval with the size of 1.5 x 1.0 cm. The tumor inside the sternum was curetted. The wall of the tumor was hard, and the deep portion was rough and irregular. The posterior table was intact. Curetted space was filled with pedicled subcutaneous fatty tissues.
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Fig 1. Plain radiogram (oblique view) showing a round translucent lesion accompanying the surrounding sclerotic region (arrowhead) in the caudal area of the right side of the manubrium of the sternum.
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Fig 2. (A) Computed tomographic findings. Mushroom-shape tumor with moderate density spreading from inside the sternum to the ventral soft tissue (open arrow) is shown. A partial defect of cortical bone in the ventral cortex is shown. (B) Magnetic resonance findings. Sagittal section of T1-weighted image of chest showing mass in lower part of manubrium and ventral soft tissue. There is no invasion of the tumor to the thoracic cavity.
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Histopathologic examination showed two types of tumor tissue; one type was spindle-shaped cells that do not form clear palisade arrangement (Antoni A) (Fig 3A), and the other consists of a loose meshwork of fibrous tissue in which the tumor cells are sparsely distributed (Antoni B) (Fig 3B). The area with Antoni A was larger than that with the latter type. Neither hyperchromic nor heteromorphic nuclei were found.
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Fig 3. Histopathologic findings. (A) Typical spindle-shape forms were seen without clear palisade pattern (Antoni type A). (B) Widely separated cells with loose intervening collagenous matrix (Antoni type B). (Hematoxylin and eosin; original magnification x100.)
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At 4 years 5 months after the operation, no local recurrence has been found, and no abnormal findings such as enlargement of the bone lesion on plain radiogram have been obtained.
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Comment
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Benign sternal tumors are rare and in general, sternal tumors should be considered malignant [4]. In deciding a surgical procedure, it is necessary to confirm diagnosis by biopsy or frozen section.
The histopathologic characteristics of intraosseous neurilemoma have been reported as follows: nuclei are hyperchromic on occasion, the area showing Antoni type A is larger than the area of type B, and the palisade arrangement is not clear [5].
There are three mechanisms proposed for how intraosseous neurilemoma develop [5]: (1) an extraosseous tumor can cause secondary erosion of bone; (2) a tumor can arise in the nutrient canal, which forms a dumbbell; or (3) a tumor can arise inside the bone. One small area of cortex is penetrated, and the tumor expands to the soft tissue outside the bone. For a neurilemoma to arise within bone, nerve must be present in the bone. This presence was demonstrated by Sherman [6]. A more likely cause would be aberrant intercostal nerve penetrating the marrow.
In this case, from the pattern of cortex defect and histologic findings, we considered that this tumor appeared to develop inside the sternum and expand to the ventral soft tissue.
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References
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Eng J., Sabanathan S., Pradhan G.N., Mearns A.J. Primary bony chest wall tumours. J R Coll Surg Edinb 1990;35:44-47.[Medline]
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In: Dahlin D.C., Unni K.K., eds. Bone tumors: general aspects and data on 8542 cases, 4th ed. Springfield: Charles C Thomas, 1986:186-192.
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Martini N., Huvos A.G., Burt M.E., et al. Predictors of survival in malignant tumors of the sternum. J Thorac Cardiovasc Surg 1996;111:96-106.[Abstract/Free Full Text]
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De La Monte S.M., Dorfman H.D., Chandra R., Malawer M. Intraosseous schwannoma: histologic features, ultrastructure, and review of the literature. Hum Pathol 1984;15:551-558.[Medline]
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Sherman M.S. The nerves of bone. J Bone Joint Surg 1963;45A:522-528.[Free Full Text]
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Abstract
Introduction
