Myxofibrosarcoma of the Breast: A Case Report

Development of a myxofibrosarcoma in the breast tissue is extremely rare. Reported here is a case of myxofibrosarcoma found in the left breast tissue of a male in his late fifties. The patient first underwent tumor resection, followed by a left mastectomy with the reconstruction of the vastus lateralis valve. The tumor comprised atypical spindle-shaped cells in a myxoid matrix with elongated blood vessels. Myxofibrosarcoma was diagnosed based on histology and immunohistochemical examination results performed for differential diagnosis. At two years and two months after the mastectomy, no local occurrence or metastasis had occurred.


Introduction
Myxofibrosarcoma generally develops in the extremities, though it sometimes occurs in the head or neck. On the other hand, a myxofibrosarcoma in the breast tissue is extremely rare, with only 18 known cases reported thus [1][2][3][4][5][6][7][8][9]. Since there are no specific markers for myxofibrosarcoma, diagnosis of occurrence in the breast tissue has been based on histology in most cases. We report a case of myxofibrosarcoma in the breast tissue with immunohistochemical examination results for differential diagnosis.

Case Presentation
The patient was a male in his late fifties, who consulted our medical center upon referral from a local doctor after findings of a left breast mass. A tumor sized 10 cm in diameter was observed in the upper region of the left breast. Ultrasound examination results indicated a well-demarcated hypoechoic tumor in the left upper area measuring 24 x 66 x 62 mm (Figure 1), while MRI showed a 68 x 34 x 84 mm tumor in the left chest wall, with low signal intensity in fat suppression T1-weighted images, high signal intensity in T2-weighted images, high signal intensity in diffusion-weighted images, and low values in apparent diffusion coefficient (ADC) maps. The MRI findings also revealed that the tumor was in extensive contact with the pectoralis major muscle along with possible adhesions, though there was no obvious indication of infiltration ( Figure 2). Needle biopsy results were highly suggestive of sarcoma, thus the patient was referred to our hospital for treatment.  The surgically resected tumor was measured at 90 x 90 x 42 mm. Gross findings showed the cut surface to be heterogeneous in color and mottled myxomatous areas, while the boundary was somewhat indistinct. Infiltration of tumor cells into surrounding adipose and pectoralis muscle tissues was also observed in some areas ( Figure 3).

FIGURE 3: Gross findings of the resected tumor
The mass was measured at 90 x 90 x 42 mm. The cut surface was heterogeneous in color and showed myxomatous areas, while the boundary of the tumor was somewhat indistinct. Infiltration into surrounding fatty and pectoralis muscle tissue was also observed.

Discussion
A myxofibrosarcoma in the breast tissue is extremely rare, with only 18 known cases reported thus [1][2][3][4][5][6][7][8][9]. Their diagnosis has been based on histology in most cases, while various immunohistochemical markers were examined for differential diagnosis in only four ( Table 2) [2,[6][7][8]. The present report provides details of a case in which diagnosis of myxofibrosarcoma in the breast tissue was determined based on histology and immunohistochemical examination results.
Recently, TLE 1 was proposed as a specific marker of synovial sarcoma [16], in addition to the combination of traditional markers such as BCL-2 and CD99. Unfortunately, TLE 1 could not be performed because of a new marker that we could not obtain. Most liposarcomas show positive findings for MDM2 and CDK4 in the cell nuclei [15]. Chondrosarcomas and malignant schwannomas also have no specific markers, though S100 and CD117 have been reported positive in 20% and 30% of chondrosarcoma cases, respectively [15], while S100 and SOX10 show focal positivity in malignant schwannomas [15]. In the present case, all of the above markers were negative ( Table 2). Therefore, the possibility of leiomyosarcoma, synovial sarcoma, liposarcoma, chondrosarcoma, and malignant schwannoma could be excluded based on immunohistochemical results.

No.
Immunohistochemistry Literature A malignant phyllodes tumor of the breast consists of pleomorphic spindle-shaped tumor cells that often show a mucinous matrix [17,18]. Diagnosis is relatively easy to obtain when the tumor contains a nonneoplastic epithelial component. However, malignant phyllodes tumors with an epithelial component that has been eradicated by tumor cells are difficult to differentiate when attempting to obtain a diagnosis of myxofibrosarcoma. In phyllodes tumor cases, positivity for PgR and AR have been reported in 100% [19], and 98% [20] of examined stromal cells, respectively. Sawyer et al. also reported that β-catenin was positive in the nuclei of stromal tumor cells in 72% of phyllodes tumors [21]. In the present tumor, PgR, AR, and nuclear β-catenin were all negative. Therefore, the possibility of a malignant phyllodes tumor, in this case, could be excluded.
Besides a malignant phyllodes tumor, some breast tumors with components of spindle cells with myxoid matrix or spindle cells with giant cells have to be listed for the differential diagnosis. These include myxofibroblastoma, and metaplastic carcinoma [22][23][24]. Especially, the exclusion of metaplastic carcinoma is very important because of the difference in the treatment strategy in advanced cases [25]. However, a component of spindle cells in metaplastic carcinoma is immunoreactive for cytokeratins though variably [22,23], while the present tumor did not express cytokeratins at all. On the other hand, myofibroblastoma is a benign tumor and its tumor cells typically express CD34, ER, PgR, and AR [15,23,24], which were not expressed in the present tumor. Therefore, both myxofibroblastoma and metaplastic carcinoma could be excluded from the differential diagnosis of the present tumor.
The five-year survival rate for a patient with myxofibrosarcoma has been reported to range from 30% to 35% [1]. Myxofibrosarcoma can metastasize to the lung, bone, and lymph node, and local recurrence following tumor resection often occurs because of an inadequate surgical procedure. Therefore, control of local recurrence by extensive tumor resection and additional radiation therapy after the resection is important [21]. Extensive tumor resection was performed in the present case, with no local occurrence or metastasis at two years and two months later.
Hartel et al. presented a clinicopathologic study of 19 cases with a primary malignant fibrous histiocytoma of the breast tissue, of which six were myxofibrosarcomas [1]. They found that such tumors were more common in middle-aged women or elderly men, with a poor prognosis for elderly patients with distant metastasis [1], as also noted in other reports of primary myxofibrosarcoma of the breast tissue [2,3,[5][6][7][8][9]. Based on reported findings of local recurrence up to three years after surgery in similar affected cases [4], long-term follow-up examinations are considered necessary for the present patient.
Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.