Metastatic high-grade myxofibrosarcoma: review of a clinical case.

We present the particular clinical and histological features of a metastatic high-grade myxofibrosarcoma (MFS) of the left buttock in a 77-year-old male patient. The tumor was biopsied and surgically removed in order to increase the patient's comfort, due to its increased size and aggressive clinical behavior. Computed tomography (CT) revealed metastases in the pleura and mediastinal lymph nodes, so limb-sparing tumor excision followed by palliative care was the best practice for the patient until the fatal outcome. The histological assessment revealed a tumor composed partly of solid sheets of spindled and pleomorphic cells, partly of areas with prominent myxoid matrix and numerous elongated capillaries. Mitotic figures are frequent, often atypical, followed by numerous giant cells with abundant eosinophilic elongated cytoplasm, resembling myoid cells often multinucleated. A panel of immunohistochemical stainings, including muscle-specific actin (MSA), S-100, CD34, desmin and myogenin were performed with a negative result, which aided excluding other soft tissue tumors like rhabdomyosarcoma and leiomyosarcomas, while Ki-67 was highly expressed in more than 70% of the tumor cells. This tumor received 6 points in accordance with the Fédération Nationale des Centres de Lutte Contre le Cancer (modified FNCLCC) and was defined as a high-grade MFS [stage IV, G3 pT2bN0M1, according to the 8th edition of TNM Classification of Malignant Tumors, ICD-O 8811÷3 in World Health Organization (WHO) Classification 2013]. Due to the clinical findings combined with the histological profile, the fatal prognosis was expected, though the time period was shorter than predicted, confirming the aggressive nature of the tumor. Even if traditionally was considered MFS as a non-metastatic lesion, recent case reports and studies, including our case revealed that this tumors in fact have the potential to be fatal due to metastatic disease.