Ann Thorac Surg 2010;89:2003-2005. doi:10.1016/j.athoracsur.2009.11.071
© 2010 The Society of Thoracic Surgeons
Case Reports
Inflammatory Malignant Fibrous Histiocytoma of Thymus Origin
Joji Samejima, MDa,*,
Ko Takahashi, MDa,
Takahiro Omori, MDa,
Koji Okudela, MD, PhDb,
Michihiko Tajiri, MD, PhDa,
Munetaka Masuda, MD, PhDc
a Department of Thoracic Surgery, Kanagawa Prefectural Cardiovascular and Respiratory Center, Yokohama, Japan
b Department of Pathology, Yokohama City University Graduate School of Medicine, Yokohama, Japan
c Department of Surgery, Yokohama City University School of Medicine, Yokohama, Japan
Accepted for publication November 23, 2009.
* Address correspondence to Dr Samejima, Department of Thoracic Surgery, Kanagawa Prefectural Cardiovascular and Respiratory Center, 6-16-1 Tomiokahigasi, Kanazawa-ku, Yokohama, 236-0051 Japan (Email: samejima{at}kanagawa-junko.jp).
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Abstract
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A 46-year-old man was referred to our department complaining of anterior chest pain. A chest computed tomographic scan revealed an anterior mediastinal tumor measuring 38 x 35 x 50 mm. Suspecting a thymoma, we performed extended thymectomy through a median sternotomy under general anesthesia. Pathologically, the tumor was composed of pleomorphic spindle-shaped cells arranged in a storiform pattern, with marked inflammatory cell infiltration. The tumor was contiguous with the thymus tissue. Based on these findings, we made the diagnosis of inflammatory malignant fibrous histiocytoma originating from the thymus. Until now, 12 months later, the patient has shown no evidence of tumor recurrence.
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Introduction
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Malignant fibrous histiocytoma (MFH) is a soft-tissue tumor that occurs most commonly in the extremities, trunk, and retroperitoneum, and there have scarcely been any reports of MFH of thymus origin. We recently encountered a patient with inflammatory MFH originating from the thymus and report this case herein, with a review of the literature.
A 46-year-old man consulted his family doctor with the complaint of anterior chest pain. A chest computed tomographic scan revealed an anterior mediastinal tumor, and the patient was referred to our department for further management. His past and family history was noncontributory. There were no remarkable findings on physical examination. The vital signs were normal. Laboratory data revealed evidence of inflammation, with elevated white blood cell count and serum C-reactive protein (white blood cell count, 12,480 /µL; C-reactive protein 1.48 mg/dL). The serum tumor marker levels were as follows: soluble interleukin-2 receptor (sIL-2R), 372 U/mL and carcinoembryonic antigen (CEA), 1.2 ng/mL. The serum titer of anti-acetylcholine receptor antibody was 1.2 nmol/L. A chest roentgenogram revealed a mass opacity in the right upper mediastinum. A chest computed tomographic scan revealed an anterior mediastinal tumor measuring 38 x 35 x 50 mm, with a well-defined margin (Fig 1). No calcification or excessive fat was seen in the tumor. No pleural effusion or lymphadenopathy was detected either. A chest magnetic resonance image indicated a mediastinal tumor with heterogeneous signal intensity. The signal intensity was intermediate on the T1-weighted images and high on the T2-weighted and diffusion-weighted images. No signs of invasion to the adjacent organs were evident. Under suspected invasive thymoma, surgery was undertaken for both definitive diagnosis and treatment. An extended thymectomy was performed through a median sternotomy under general anesthesia. The tumor was strongly adherent to the pericardium, left brachiocephalic vein, and ascending aorta; however, there was no evidence of invasion of any of these structures. Histopathologic examination of the resected specimens revealed that the tumor was firm and elastic, with clear boundaries and a white cut surface measuring 40 x 40 mm. The tumor was contiguous with the thymus tissue. Histopathologically, the tumor cells were composed of pleomorphic spindle-shaped cells arranged in a storiform pattern, associated with pleomorphic giant cells and atypical mitotic figures. Marked infiltration by a variety of inflammatory cells (ie, neutrophils, eosinophils, lymphocytes, and plasma cells) was observed (Fig 2A). Hassall's bodies were detected, and the tumor was pathologically contiguous with the thymus tissue. Immunohistochemical staining for cytokeratin AE1/AE3, which suggests epithelial cell origin, was negative. The cells were also negative for CD21, CD35, and CD23, which point to a dendritic cell line of differentiation. On the other hand, immunohistochemical staining was positive for 
1-antitrypsin and slightly positive for CD68 expression, pointing toward a histiocytic lineage (Fig 2B). Based on these findings, a pathologic diagnosis of inflammatory MFH originating from the thymus was made. The surgical margin was negative. After an uneventful postoperative course, the patient was discharged from our hospital on day 9 after the operation. Because he did not wish to undergo mediastinal irradiation, we decided to follow-up closely with him at the outpatient department. Until now, 12 months since then, the patient has shown no evidence of tumor recurrence.
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Fig 1. Chest computed tomographic scan showing an anterior mediastinal tumor, measuring 38 x 35 x 50 mm, with a well-defined margin. No pleural effusion or lymphadenopathy was detected.
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Fig 2. (A) The tumor was composed of pleomorphic, spindle-shaped cells arranged in a storiform pattern, with pleomorphic giant cells and atypical mitotic figures. Marked infiltration by a variety of inflammatory cells was observed. (Hematoxylin and eosin stain; x20.) (B) Immunohistochemical staining was positive for a1-antitrypsin (x20).
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Comment
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Malignant fibrous histiocytoma is the most frequently encountered soft-tissue sarcoma in late adult life. Malignant fibrous histiocytoma was first described in the 1960s as one of a group of lesions presumably derived from a mixed histiocytic and fibroblastic lineage [1], which occurs most commonly in the extremities (lower extremities, 49% [particularly in the thigh, 30%] and upper extremities, 19%), followed by the retroperitoneum and abdomen (16%). Malignant fibrous histiocytoma typically arises from the skeletal muscle (59%) and deep fascia (19%) [2]. In 1976, Harrowe and colleaguesreported MFH originating from the mediastinum for the first time. More recently, Murakawa and colleagues [3] reviewed 34 cases of mediastinal MFH, including 10 cases of anterior mediastinal origin. Reports of MFH originating from the thymus are particularly scarce [4].
The histologically protean characteristics of the tumor were described by Weiss and Enzinger [2] because of the diverse morphological characteristics, in which it is often difficult to differentiate MFH from some other malignant neoplasms characterized by the presence of polymorphic cells (eg, liposarcoma, leiomyosarcoma, fibrosarcoma, and rhabdomyosarcoma). The pathologic criteria for the diagnosis of MFH are as follows: being composed of fibroblast-like and histiocyte-like cells in various proportions, arranged in a storiform pattern, with the presence of bizarre giant cells and inflammatory cells. The findings in our patient satisfied these criteria. In addition, 1-antitrypsin is considered to be a useful marker for MFH [5]. The seropositivity for 1-antitrypsin in our patient supported the diagnosis of MFH. Malignant fibrous histiocytoma is classified into five histologic subtypes, as follows: (1) storiform-pleomorphic type (most common), (2) myxoid type (eg, myxofibrosarcoma), (3) giant cell type, (4) inflammatory type, and (5) angiomatoid type (most of these occur in young adults and show low-grade malignancy). No prognostic differences have been described among the histologic subtypes [6]. The tumor in our case was concluded to be an inflammatory type, because marked polymorphonuclear leukocytic infiltration was noted.
A few characteristic imaging findings of MFH have been described. Fat suppression on magnetic resonance imaging is useful for distinguishing MFH from some liposarcomas. Magnetic resonance imaging may be useful to evaluate the relations between the tumor and the adjacent organs. However, biopsy is considered to be the most reliable for a definitive diagnosis.
As for treatment of MFH, surgical resection plays a central role. The extent of resection remains controversial; however, radical resection for mediastinal MFH may be difficult because of the location of the tumor. Adjuvant radiotherapy has been reported to reduce the incidence of local recurrence, but not the overall survival [7]. A meta-analysis has provided evidence that chemotherapy improved the time-to-local and time-to-distant recurrence and the overall recurrence-free survival, but not the overall survival [8]. Despite not receiving adjuvant radiotherapy or chemotherapy, our patient has shown no evidence of tumor recurrence until now, approximately 12 months after the diagnosis. However, careful and close follow-up will be necessary.
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References
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- O'Brien JE, Stout AP. Malignant fibrous xanthomas Cancer 1964;17:1445-1455.[Medline]
- Weiss SW, Enzinger FM. Malignant fibrous histiocytoma: an analysis of 200 cases Cancer 1978;41:2250-2266.[Medline]
- Murakawa T, Nakajima J, Fukami T, et al. Malignant fibrous histiocytoma in the anterior mediastinum Jpn J Thorac Cardiovasc Surg 2001;49:722-727.[Medline]
- Imai K, Saito H, Minamiya Y, et al. Malignant fibrous histiocytoma originating from the thymus Gen Thorac Cardiovasc Surg 2008;56:606-609.[Medline]
- Chowdhury LN, Swerdlow MA, Jao W, et al. Post-irradiation malignant fibrous histiocytoma of the lung. Demonstration of alpha 1-antitrypsin-like material in neoplastic cells. Am J Clin Pathol 1980;74:820-826.[Medline]
- Oda Y, Tamiya S, Oshiro Y, et al. Reassessment and clinicopathological prognostic factors of malignant fibrous histiocytoma of soft parts Pathol Int 2002;52:595-606.[Medline]
- Yang JC, Chang AE, Baker AR, et al. Randomized prospective study of the benefit of adjuvant radiation therapy in the treatment of soft tissue sarcomas of the extremity J Clin Oncol 1998;16:197-203.[Abstract/Free Full Text]
- Sarcoma meta-analysis collaboration Adjuvant chemotherapy for localized resectable soft-tissue sarcoma of adults: meta-analysis of individual data Lancet 1997;350:1647-1654.[Medline]
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Abstract
Introduction
