| Abstract|| |
Malignant fibrous histiocytoma (MFH) is uncommon within the central nervous system. MFH is a malignant tumor composed of a mixture of fibroblastic and histiocytic cells, and is also known as pleomorphic fibrous xanthoma, malignant fibrous xanthoma, and pleomorphic fibrous histiocytoma. It is a pleomorphic sarcoma originally found in soft tissue and there are few reported cases within the central nervous system, in particular the cerebellum. To the best of my knowledge, this is third case arising from the cerebellum. This tumor is difficult to diagnose and may be difficult to treat.
Keywords: Cerebellum, immunohistochemistry, malignant fibrous histiocytoma, sarcoma
|How to cite this article:|
Gelincik I. Cerebellar malignant fibrous histiocytoma. Indian J Pathol Microbiol 2012;55:402-5
| Introduction|| |
Malignant fibrous histiocytoma (MFH) is defined as a group of pleomorphic sarcomas which shows no line of differentiation.  The site of primary origin tends to be mainly in the extremities followed by the trunk, the head, and the neck. It is the most common soft-tissue sarcoma with the peak incidence in the seventh decade. MFH are rare tumors within the central nervous system. They are pleomorphic sarcomas that were originally observed in soft tissue.  However, they have been reported in the brain, duramater, cranial bones, spine and peripheral nerves.  Intracranial MFH may occur at any age with no sex predominance. The average age is 38 years, but one quarter of reported cases are among children. When seen intracranially, they are normally supratentorial but can arise in the frontal, temporal or parietal lobe, or be intraventricular, within the sellar, the cerebellum or at the cerebellopontine angle.
| Case Report|| |
A 65-year-old man presented with a 8-week history of all day occipital headache, dizziness and vomiting. The patient was admitted to intensive care. He had no significant past medical history, any prior history of surgical trauma/radiotherapy to head and neck region and was not on regular medication. On neurological examination, he had weakness alert, orientation and displayed left cerebellar signs. Brain magnetic resonance imaging (MRI) was performed, and the T1-weighted image revealed 6 × 4 × 4 cm, oval and relatively irregular margins, isohyperintensity lesion in the left cerebellar hemisphere of the posterior fossa [Figure 1]. There was surrounding edema and effacement of the fourth ventricle with subsequent triventricular hydrocephalus. The patient underwent left suboccipital craniotomy and excision of the tumor. Intraoperatively the tumor was very vascular, gritty, necrotic in some areas and in the left cerebellar hemisphere. The breast ultrasonographic, bone scintigraphic, and thoracoabdominal computed tomographic findings were normal.
Histopathological study of the cerebellum showed focal involvement of the cerebellum by neoplastic cell aggregation [Figure 2]a. Hematoxylin and eosin (H & E)-stained slides revealed anaplastic proliferation of atypical nuclei with moderate cytoplasms or oval-shaped cells admixed with atypical giant cells [Figure 2]b apopitotic cells, focal necrosis and mitosis [Figure 2]c. Mitotic figures were also easily identified. For further investigation, immunohistochemistry panels were performed. Ki67 staining for MIB-1 labeling was determined by an increase in mitotic activity [Figure 2]d. The immunophenotyping studies suggested a strong positive reaction for vimentin [Figure 3]a and focally positive staining for CD68 [Figure 3]b, pancytokeratin [Figure 3]c and smooth actin [Figure 3]d. However, tumor cells had negative reactions to desmin, HMB 45, leukocyte common antigen (LCA), S-100 protein, glial fibrillary acidic protein (GFAP), epithelial membrane antigen (EMA), CD34 and CD31. Without any response to the antibiotic, the patient died within the first week after surgery. Based on these findings, the histological diagnosis was MFH.
|Figure 1: Magnetic resonance imaging (MRI) showing 6 × 4 × 4 cm, oval and relatively irregular margins extra-axial left cerebellar hemispheral lesion of isohyperintensity in T1-weighted image (a): coronal, (b): and sagitial|
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|Figure 2: Hematoxylin and Eosin-stained slides and Ki67 staining for MIB-1 labeling (a): Histopathological study of the cerebellum showed focal involvement of the cerebellum (arrow head) by neoplastic cell aggregation (arrow) (H and E; × 200). (b): Photomicrograph revealed anaplastic proliferation of atypical nuclei with moderate cytoplasms or oval-shaped cells admixed with atypical giant cells (H and E; × 400), (c): and apopitotic cells, focal necrosis and mitosis (H and E; × 400). (d): Tumor cells showing a brisk rate of Ki67 proliferation (Ki67; × 400)|
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|Figure 3: Immunostained slides (a): Strong and diff use vimentin immunostaining in tumoral cells (IHC; × 400). (b): A few cells are positive with CD 68 (IHC; × 200). (c): A few cells are posi ve with pancytokeratin (IHC; × 200). (d): A few cells are positive with smooth muscle actin (IHC; × 200)|
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| Discussion|| |
Sarcomas are malignant mesenchymal tumors that account for a low percentage of all brain tumors.  Intracranial MFH is an extremely rare tumor. It can originate in the central nervous system or arise as a metastasis from a primary extracranial tumor. , and there are few reported cases within the central nervous system, in particular the cerebellum. Here, a case of MFH in the cerebellum is described.
Pathologically the tumor consists of histiocyte and fibroblast cells, thus a tumor of mesenchymal origin. Both the fibroblasts and histiocytes synthesise reticulin, collagen and a basement membrane like granular material around the neoplastic cells.  It may be connected to the meninges, may be vascular and may invade the brain. The tumor can also metastasise via the cerebrospinal fluid or be a metastases from a soft tissue primary.  Males are affected more commonly than females with peak incidence in the sixth decade of life.  Our case is a man.
There are six histological subtypes: storiformpleomorphic, giant cell, inflammatory, atypical, myxoid and angiomatoid type.  The latter two subtypes were excluded by the World Health Organization (WHO) classification in 2002.  The myxoid subtype accounts for about one quarter of all the MFHs reported worldwide and were reclassified as myxoid fibrosarcoma because of its distinctive pathological characteristics and better prognosis than other subtypes. The angiomatoid subtype was renamed as angiomatoid fibrous histiocytoma. All of the tumors were classified as high-grade sarcomas, a grade 2 or grade 3 on a three-tiered grading system.
Microscopically, MFH is composed of collagen-forming spindle cell proliferation arranged in a storiform or cartwheel pattern accompanied by varying numbers of inflammatory cells, foam cells, and siderophages. Commonly benign and malignant giant cells are seen. , Malignancy is determined by an increase in mitotic activity.  The tumor in the present case was diagnosed as MFH since the pathology showed undifferentiated proliferation of atypical nuclei with moderate cytoplasms or oval-shaped cells admixed with atypical giant cells and mitosis. Mitotic figures were pronounced. Histologically, diagnosis is aided by immune staining. Typically, there is an absence of GFAP, S100, EMA, desmin, HMB 45, LCA, CD34 and CD31 staining as in this case. GFAP staining will aid differentiation from a pleomorphic xanthoastrocytoma and gliosarcoma, which are glial origin tumors. MFH show a definable line of differentiation, foremost among which are the pleomorphic variants of leiomyosarcoma and carcinomas. The presence of just rare cells showing positivity for epithelial (positivity for pancytokeratin) or myogenic antigens (positivity for smooth actin) most often has little significance and does not, of itself, exclude this diagnosis. There is strong and diffuse positivity with vimentin and focally positive staining for CD68, pancytokeratin and smooth actin in tumoral cells, also seen in this case.  The differential diagnoses to exclude are metastases, gliosarcoma, glioblastoma and xanthoastrocytoma, Langerhans cell histiocytosis, lymphomas and meningeal sarcoma. , LCA staining will aid differentiation from lymphoid origin tumors.
Without any response to the antibiotics and with a progressive deterioration of neurologic and mental condition, the patient died within the first week after surgery. The ultimate prognosis remains unclear due to the small numbers of patients with this tumor. Rarity of MFH in the cerebellum does not eliminate their importance as they have clinical resemblance to other intracerebellar tumors and they are also associated with a very poor prognosis.
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Bolge Egitim ve Arastirma Hastanesi, Patoloji Klinigi Cat Yolu cad. Yildizkent-Erzurum
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]