Intramuscular high-grade myxofibrosarcoma of left buttock of 66-year-old male patient - approach to systematic histopathological reporting.

Here we present a systematic approach to histopathological reporting of high-grade myxofibrosarcoma of 66-year-old male patient. The tumor was biopsied with fine-needle aspiration (FNA) and core-needle biopsy (CNB) and then the whole myxoid tumor was excised with left musculus gluteus maximus. The lesion was stained with Hematoxylin-Eosin (HE), Periodic acid-Schiff (PAS), Alcian blue, Masson's trichrome, Ki67, alpha-smooth muscle actin (α-SMA), S100, CD34 and vimentin. FNA material grounded the diagnosis of non-epithelial neoplasia, while CNB was enough to produce diagnosis of myxoid sarcoma. The tumor lied under superficial fascia with no extension beyond deep fascia or any invasion of skin, vessels or nerves, either. The tumor was intramuscular, mainly myxoid with hypercellular areas of highly atypical cells with bizarre giant multinucleated cells that clearly belonged to category of high-grade sarcoma. According to Fédération Nationale des Centres de Lutte Contre le Cancer (FNCLCC), the case was assessed for 5 points. Ki67 index reached more than 80% malignant cells. Alcian blue was strongly positive in myxoid background. Masson's trichrome emphasized fibrillary structure of tumor. Negativity for S100, α-SMA with strong co-expression of CD34 and vimentin supported the diagnosis of myxofibrosarcoma. The lesion was diagnosed as high-grade myxo-fibrosarcoma (formerly myxoid malignant fibrous histiocytoma) G2 pT2b [7th edition pTNM (pathological tumor-node-metastasis), code ICD-O 8811/3 in World Health Organization (WHO) Classification 2013]. In approach to diagnosis of soft tissue malignancies, a strict sequence of procedures should be applied as only meticulous and ordered diagnostic pathway would succeed in and correct identification of a peculiar type of sarcoma.