Malignant fibrous histiocytoma arising in the upper posterior triangle of the neck.
We describe the case of a 59-year-old man who came to us with a right neck mass of 4 to 5 months' duration. A histologic diagnosis of malignant fibrous histiocytoma was made, and the patient underwent wide local excision and neck dissection followed by postoperative radiation therapy. We briefly discuss the characteristics and treatment of this rare entity.
Malignant fibrous histiocytomas--first described by O'Brien and Stout in 1964--are high-grade, pleomorphic, soft-tissue sarcomas.  They are primarily made up of spindle cells arranged in a storiform pattern and admixed with histiocyte-like cells. Because of the dichotomous distribution of cells in these tumors, there is controversy over their histogenesis. Recent immunohistochemical studies suggest that the basic cell is the fibroblast or myofibroblast and that histiocytic differentiation is either variable or absent.  The pleomorphic cell type and the broad histologic appearance, which can include myxoid or hemangiocytomatous features, make the pathologic identification of these tumors difficult and require that they be differentiated from other sarcomas that have a pleomorphic appearance.
Malignant fibrous histiocytomas usually involve the extremities and retroperitoneum. These tumors are relatively rare in the head and neck region, accounting for only I to 3% of all cases of malignant fibrous histiocytoma.  Fewer than 200 head and neck cases have been reported in the literature.  In this article, we describe a new case of malignant fibrous histiocytoma that arose in the upper posterior triangle of the neck and involved the posterosuperior portion of the right sternocleidomastoid muscle.
A 59-year-old man came to our VA center with a right neck mass of 4 to 5 months' duration. He denied any pain or symptoms associated with the mass, and he denied any recent change in weight. He had no history of radiation exposure or trauma to the area.
Examination revealed a firm 2.5-cm mass over the posterosuperior border of the right sternocleidomastoid muscle inferior to the mastoid process. The mass was nontender and mobile, and no cervical lymphadenopathy was appreciated. Fine-needle aspiration cytology revealed a spindle-cell lesion. Computed tomography (CT) demonstrated a multilobulated and uniformly enhancing soft-tissue mass. The mass was inseparable from the posterior aspect of the right stemocleidomastoid muscle; it abutted but did not infiltrate the muscles forming the floor of the right posterior triangle (figure 1). Biopsy examination revealed that it was a malignant fibrous histiocytoma. CT of the chest was negative for pulmonary metastasis.
The patient was taken to the operating room for wide excision of the mass, including resection of the floor of the neck musculature and neck dissection of levels II, III, and V; the sternocleidomastoid muscle and spinal accessory nerve were sacrificed. The pathology report noted an area suspicious for a positive margin, and the patient underwent further resection of the area; subsequent pathologic examination failed to find any residual tumor. The patient recovered well and was referred for postoperative radiotherapy.
Microscopically, the mass contained spindle cells arranged in a storiform pattern. In addition, multinucleated, histiocyte-like cells were found interspersed between the spindle cells (figure 2). Mitotic activity was prominent, and small areas of necrosis were noted. Immunohistochemical staining results included bright positivity for muscle-specific actin (1A4) and vimentin (V9) (figure 3A). About 20 to 30% of the cells stained for S-100 protein (rabbit polyclonal antiserum). Many of the spindle cells and all of the multinucleated cells were positive for CD68 (KP1), a histiocytic marker (figure 3B). The tumor cells were also positive for keratins (AE1/AE3 and 35BH11), but they were negative for melanoma-specific antigen (HMB45) and CD34 (QBEND/10). Fewer than 5% of the cells were positive for Ki-67 (MIB-1).
Electron microscopic examination was performed on tissue retrieved from one of the paraffin blocks of the resected tumor. The spindle cells showed myofibroblastic differentiation (figure 4). Some, however, were characterized by the presence of many lysosomal granules in the cytoplasm. These cells tended to be multinucleated. The light microscopic, immunohistochemical, and electron microscopic findings were considered to be diagnostic of a malignant fibrous histiocytoma.
Etiology. No etiologic factors have been identified for malignant fibrous histiocytoma, but radiation exposure is suspected to play a causal role. Possible associations with Paget' s disease or bone infarcts have also been described. 
Clinical presentation. All subtypes of malignant fibrous histiocytoma occur in patients between the ages of 50 and 70 years, with the exception of the angiomatoid variant.  In the head and neck, most cases of malignant fibrous histiocytoma are storiform-pleomorphic or myxoid variants. These tumors most often occur in the region of the sinonasal tract (30%), craniofacial bones (15 to 20%), larynx (10 to 15%), soft tissue of the neck (10 to 15%), major salivary glands (5 to 15%), and oral cavity (5 to 15%).  A malignant fibrous histiocytoma of the oral cavity, parotid, or neck usually appears as a painless enlarging mass. A number of other diverse symptoms can also be seen, including dyspnea, hoarseness, hemoptysis, cranial nerve palsy, paresthesia, and epistaxis, depending on the tumor's site of origin. These tumors are more common in men than women (61%). 
Diagnosis. The histologic diagnosis of malignant fibrous histiocytoma of the head and neck can be challenging, especially with small biopsy specimens (multiple biopsies are sometimes required). In some instances, the diagnosis can be established with confidence only when the entire tumor has been excised and thoroughly examined. Diagnosis requires an adequate biopsy for electron microscopy and special stains.
Farhood et al reviewed 176 cases of soft-tissue sarcoma of the head and neck that had been treated at Memorial Sloan-Kettering Cancer Center in New York City between 1950 and 1985 and identified only seven cases of malignant fibrous histiocytoma.  They believed that limited biopsy material, such as that obtained from tissue core or needle aspirate, should not be regarded as optimal for making a definitive diagnosis of primary soft-tissue tumors. In their series, all patients had undergone a formal tissue biopsy prior to definitive treatment. This was also our experience; two previous fine-needle aspirations in our patient had failed to provide a definitive diagnosis. We were able to arrive at a diagnosis of malignant fibrous histiocytoma only after an open biopsy.
Differential diagnosis. At least nine entities should be considered in the differential diagnosis. They include atypical fibroxanthoma, spindle-cell carcinoma, amelanotic malignant mucosal melanoma, osteosarcoma, fibrosarcoma, pleomorphic rhabdomyosarcoma, pleomorphic liposarcoma, dedifferentiated sarcomas, and glioblastoma multiforme. 
Treatment. The rarity of malignant fibrous histiocytoma has precluded any one individual from acquiring sufficient experience to reach any meaningful conclusions regarding the most appropriate therapy. However, as with sarcomas at other sites, surgical excision of tumors in the head and neck region remains the definitive treatment. The extent and adequacy of excision will largely determine the incidence of local recurrence and survival. Extracapsular enucleation of the tumor will result in up to a 90% local recurrence rate because of the presence of microscopic pseudopodia, which tend to grow through the pseudocapsule. According to Weber et al, a positive surgical margin is the single most important factor leading to local failure.  Thus, wide excision, usually defined in the limb as 5 cm outside the capsule, is the recommended treatment and is associated with a better prognosis.
In the head and neck, however, wide excision is rarely possible because of a tumor's close proximity to neurovascular and other vital structures that cannot be resected without the risk of severe morbidity.  Thus, wide resection is only rarely possible. This raises the need for adjuvant therapy. Although the data on postoperative radiation therapy are limited, some authors advocate its use based on studies of the treatment of other types of soft-tissue sarcomas of the head and neck. [10,11] For example, Eeles et al reported a better local control rate at 5 years with the use of combined-modality treatment (60%) than with surgery alone (40%).  Based on these and other findings and on the high incidence of local recurrence, they advocate the use of postoperative radiotherapy in most cases. [4,10,11]
The review of 176 cases by Farhood et al showed that after definitive surgical treatment, the margins of the surgical specimens were pathologically positive in 79 patients (44.9%), negative in 56 (31.8%), and unknown in 41 (23.3%).  The pathologic status of the margins was significantly correlated with survival. Patients with negative margins had a 5-year survival rate of 85%, while those with positive margins had a 5-year survival of only 28%. After they were identified as having pathologically positive margins, 23 of the 79 patients underwent reexcision. However, surgical attempts failed to secure free margins in 21 patients, and 20 of them eventually died of disease. Farhood et al also reported that 11 of 22 patients (50%) who had high-grade sarcomas, including malignant fibrous histiocytoma, eventually died of disease, even when their margins were free. They wrote that the dismal prognosis of high-grade soft-tissue sarcomas calls for improved treatment strategies. 
Frankenthaler et al reviewed the records of 118 patients who had been treated at the M.D. Anderson Cancer Center in Houston for soft-tissue fibrosarcoma of the head and neck; this population included 32 patients who had malignant fibrous histiocytoma.  Of those patients who had been treated with surgery, surgical margins were negative in 53%, positive in 26%, and unknown in 21%. In patients with positive margins, postoperative external-beam radiation was delivered from a cobalt-60 source, but it did not improve survival. Frankenthaler et al felt that wide local excision should remain the treatment of choice when possible and that the poor prognosis for malignant fibrous histiocytoma is unaffected by combined surgical and radiation treatments.
The reported rate of systemic metastases in patients with malignant fibrous histiocytoma of the head and neck ranges from 25 to 35%.  The most common sites of metastasis are the lung, regional lymph nodes, liver, and bone.  Chemotherapy should be administered when there is evidence of a distant metastasis. Doxorubicin has been shown to be the single most effective agent against these tumors. 
Another question that remains unanswered concerns the role of neck dissection. The incidence of dissemination to cervical lymph nodes has been reported to range from 0 to 15%.  There is evidence that tumors arising from the oral soft tissues are more likely to be associated with positive cervical lymph nodes.  Some authors advocate the addition of lymph node dissection to the planned surgery because it might confer a small survival advantage.  Barnes and Kanbour reported 12 cases of malignant fibrous histiocytoma of the head and neck that were treated with (two patients) and without (10 patients) postoperative radiation therapy.  Four patients also underwent simultaneous radical or modified radical neck dissection. All neck dissection specimens were free of tumor. Barnes and Kanbour thus advocated that neck dissection not be done electively, but only when there is strong clinical or histologic evidence of metastasis or in order to achieve an adequate margin of resection.  We performed neck di ssection on our patient because of the location of his tumor in the neck. The final pathology report failed to reveal any regional metastasis.
Prognosis. Malignant fibrous histiocytoma is very aggressive. According to Weiss and Enzinger, 2-year survival rates are approximately 60%, and there is a high incidence of local recurrence (44%) and metastasis (44%).  The most common sites of metastasis are the lung, regional lymph nodes, liver, and bone.  Hutchinson and Friedberg reported a 5-year survival rate of 60% and a 10-year rate of 40%.  The prognosis for patients with head and neck sarcoma is significantly worse than that of patients whose tumors arise in the extremities or in truncal sites. Head and neck sarcomas have a higher rate of local recurrence than those of all other sites except the retroperitoneum.  According to Weber et al, a positive surgical margin is the single most important reason for local failure. 
Important clinical predictors of a poor outcome are male sex, advanced age, underlying systemic illness, large primary tumors, tumors arising from bone, and deep-seated tumors. In the head and neck region, the worst prognoses are for tumors arising from the maxillary sinus (60% metastasis, 40% fatality), the mandible (40 and 30%), and the larynx (22 and 44%). Patients who have radiation-associated lesions also appear to fare poorly. Similarly, patients with systemic conditions such as leukemia, Niemann-Pick disease, and bone infarcts also have a poor prognosis. 
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|Comment:||Malignant fibrous histiocytoma arising in the upper posterior triangle of the neck.|
|Publication:||Ear, Nose and Throat Journal|
|Article Type:||Brief Article|
|Date:||Aug 1, 2001|
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