Ann Thorac Surg 2000;70:1718-1720
© 2000 The Society of Thoracic Surgeons
Case report
Myositis ossificans of the chest wall simulating malignant neoplasm
Joung Taek Kim, MDa,
Yong Han Yoon, MDa,b,c,
Wan Ki Baek, MDa,b,c,
Jae Yul Han, MDa,b,c,
Young Chae Chu, MDa,b,c,
Hyung-Jin Kim, MDa,b,c
a Departments of Thoracic and Cardiovascular Surgery, Inha University Hospital, Inchon, South Korea
b Department of Pathology, Inha University Hospital, Inchon, South Korea
c Department of Radiology, Inha University Hospital, Inchon, South Korea
Address reprint requests to Dr Joung Taek Kim, Department of Thoracic and Cardiovascular Surgery, Inha University Hospital, 7-206 Shinheung-dong 3 GA, Junggu, Inchon 400-103, Korea
e-mail: jtkim{at}inha.ac.kr
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Abstract
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Myositis ossificans originating from the chest wall is extremely rare. We report a case of myositis ossificans occurring in a young woman with progressive painful swelling in the chest wall. Preoperative examination suggested a malignant neoplasm originating from soft tissue. Although rare, myositis ossificans is one of the potential causes of painful swelling in the chest wall, and can be mistaken for a malignant neoplasm.
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Introduction
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Myositis ossificans is a benign condition of heterotopic bone formation. Extremities are known as the most common anatomical site of MO. We report a case of myositis ossificans of the chest wall, initially thought to be a malignant neoplasm on preoperative examination.
An 18-year-old woman was referred from a private clinic with complaints of tenderness and swelling in the right submammary area. She denied any previous illness including trauma. Rib series showed a soft tissue mass in the chest wall in the right fifth intercostal space. Thin linear periosteal reactions were also noted along the margins of the fifth and sixth ribs. Computed tomography of the chest showed 4 x 5 cm soft tissue mass containing several calcifications in the right anterolateral chest wall.
The patient underwent whole body bone scan and chest magnetic resonance imagining. There was no hot uptake on whole body bone scan. As compared to signal intensity of chest wall musculature on magnetic resonance imaging, the mass showed isointense and heterogeneously hyperintense signals on T1 and T2 weighted images, respectively. After contrast enhancement, the mass enhanced significantly. There was thin linear periosteal reaction along the margins of adjacent ribs, which suggested malignancy (Fig 1).
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Fig 1. T2-weighted MR image shows relatively well-margined hyperintense mass in the right chest wall. There is no invasion of the tumor to the thoracic cavity.
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The laboratory results including alkaline phosphatase were completely normal. Percutaneous needle aspiration cytology was done for histologic diagnosis. The aspiration smear showed scanty cellularity. Only a few inflammatory cells and giant cells were seen. Surgical exploration was done via small submammary incision under the impression of malignant neoplasm. At operation, a circumscribed 4 x 5 cm hard mass was found in the fifth intercostal space under the serratus anterior muscle. The parietal pleura under the mass were thickened. The mass was excised together with the attached fifth and sixth ribs (Fig 2A). The cut surface of the mass showed a shell of bony tissue with a more or less soft, red-brown central area surrounded by small amounts of residual muscle tissue. Microscopically, the typical zonal pattern showing a fibroblastic center and a broad zone of ossification at the periphery was seen (Fig 2B).
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Fig 2. Pathologic findings. (A) Cut surface of the mass showed a hemorrhagic area surrounded by a broad zone of ossification and small amounts of residual muscle tissue. (B) Lower power microscopic findings reveal the typical zonal pattern: a fibroblastic center and a broad zone of ossification at the periphery (Hematoxylin and eosin staining, magnification x 12.5).
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No sign of recurrence was detected on examination 8 months after the operation. The chest wall pain had subsided.
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Comment
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Myositis ossificans, a benign, ossifying soft tissue mass, has been described by various names including heterotopic ossification, pseudomalignant osseous tumor of soft tissue, extra-osseous localized nonneoplastic bone and cartilage formation, myositis ossificans circumscripta, and pseudomalignant myositis ossificans [1]. Usually, young adults, generally athletic, present with a painful soft-tissue mass located in the greater musculature of the limbs [2]. Location in the chest wall is extremely rare [3]. Although there is frequently a previous history of trauma, 40% to 60% of patients have no history of prior trauma [1, 2, 4]. The condition can be classified as follows: (1) myositis ossificans progressiva, (2) myositis ossificans traumatica, (3) myositis ossificans associated with neuromuscular and chronic disease, and (4) nontraumatic myositis ossificans [5]. Young adult women are more susceptible to nontraumatic myositis ossificans [5]. Our case seems to belong to nontraumatic myositis ossificans.
The lesion comprises a wide range of histologic features from osteoma-like to osteosarcoma-like appearance [6]. In the normal evolution of myositis ossificans, the first week after a traumatic event is characterized by an active spindle cell proliferation with mitotic activity. During the 2nd week, there is formation of primitive cartilage and woven bone, which, at 2 to 5 weeks, becomes clearly trabecular. A late phase (after 6 weeks) will show a cellular center containing plump mesenchymal cells surrounded by osteoid and a rim of lamellar bone [2, 5]. Difficulties in differentiating these lesions from osteogenic sarcoma were described in the literature [1–8]. A malignancy can be suspected radiolographically and histologically if a radiographic examination and a biopsy are obtained at an early stage or only from the center of the lesion [2, 5, 7]. Angervall and associates [8] called this benign lesion "pseudomalignant osseous tumor of soft tissue."
Various treatments have been suggested including simple observation, steroids, low vitamin D diet, and surgical excision [2, 3, 5–7]. Sporadic reports have revealed a few cases of malignant transformation of myositis ossificans. When local excision was performed, follow-up demonstrated little risk of recurrence and no malignant transformation [5, 6, 8].
Despite the extreme rarity, there is a need for better knowledge of myositis ossificans arising from the chest wall to avoid clinical misdiagnosis as malignant chest wall tumor.
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References
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Wei-Jen S., Michael T.H., Kelly G., et al. Myositis ossificans demonstrated by positive gallium-67 and technetium-99m-HMDP bone imaging but negative technetium-99m-MIBI imaging. J Nucl Med Technol 1999;27:48-50.[Abstract]
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Angervall L., Stener I., Aheren C. Pseudomalignant osseous tumor of soft tissue. J Bone Joint Surg 1969;51B:654-663.
Accepted for publication January 20, 2000.
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Abstract
Introduction
