Myxoid Liposarcoma with Cartilaginous Differentiation: A Case Study with Cytogenetical Analysis
A 45-year-old female visited the hospital with a palpable mass on the medial aspect of her thigh. The mass was observed by the patient 3 months previously and the size was perceived to be rapidly increasing. Computed tomography of the site showed an 11 cm-sized well-circumscribed mass with heterogeneous intensity, calcification and septation (). A diagnostic incisional biopsy was performed, and the tissue that was biopsied showed cartilage with atypical cytological features and focal necrosis. Analysis determined that myxoid stroma surrounded the cartilage, with the presence of some scattered lipoblasts within the myxoid stroma. Based on these findings, the biopsy was diagnosed as a malignant cartilage-forming tumor, and wide excision was performed on the entire mass. The specimen exhibited a well-demarcated ovoid mass with lobulation (), and each lobulated area was found to have different appearances that ranged from a solid gray fibrotic firm lobule, to a brown fibrotic soft lobule with a focal hemorrhage and cystic change, to a solid gray lobule with a focal glistening translucent myxoid appearance and a bluish firm resilient area with a focal calcification. Microscopic analysis revealed that the solid gray fibrotic area showed diffuse proliferation of bland fusiform cells with ovoid elongated nuclei and a moderate to abundant cytoplasm, and fine, delicate capillary vessel networks were noted within the fibrotic area (). The brown fibrotic and hemorrhagic area contained coagulative necrosis of bland fusiform cells with hemorrhage, and a previous biopsy was proposed as the cause for the change in tissue. The myxoid area was characterized by a prominent basophilic myxoid matrix with scattered bland fusiform cells and lipoblasts (). The lipoblasts had eccentrically located, small, elongated nuclei that were pushed to the periphery of the cell by clear, abundant intracytoplasmic vacuoles. The bluish resilient areas, which accounted for about 10% of the tumor volume, were characterized by cartilage with enchondral ossification, which showed mature bone without osteoid (). The cartilage was moderately cellular and was composed of chondrocytes with atypical nuclei. Based on the immunohistochemistry, some of the fusiform cells and the lipoblasts were determined to be S-100 protein positive (1:300, Thermo Fisher Scientific, Waltham, MA, USA) (), but were negative for smooth muscle actin (1:500, Dako, Glostrup, Denmark), desmin (1:1,000, Dako), and myogenin (1:100, Dako). Less than 5% of the cells were determined to be p53 positive (1:1,000, Dako) (), and the Ki-67 (1:100, Dako) labeling index was also less than 5%. Based on these findings, a diagnosis of myxoid liposarcoma was considered. Molecular evaluation was performed on both the typical myxoid liposarcomatous and the cartilaginous areas, to confirm the proposed diagnosis. The final diagnosis was determined to be myxoid liposarcoma with cartilaginous differentiation, and the patient was scheduled for radiation therapy because the tumor was very close to the resection margin. Currently, after 6 months of follow-up, the patient has not presented with any evidence of metastasis or reoccurrence.\nTypical myxoid liposarcomatous and cartilaginous areas were marked on a paraffin block after the hematoxylin and eosin slides were reviewed. Five 10 µm sections of each area were cut from the resection specimen blocks and placed into Eppendorf tubes. The total RNA was extracted from the formalin-fixed, paraffin embedded samples using an RNeasy mini kit (Qiagen, Valencia, CA, USA) following the manufacturer's instructions. After preparation, 1 µg of each of the total RNA samples were reverse transcribed using a RevertAid First Strand cDNA Synthesis kit (Thermo Fisher Scientific), and a nested polymerase chain reaction (PCR) was performed using outer and inner primer sets that were based on a previous report. The outer primer set was TLS-CHOP outer forward (5'-AGCAAAGCTATAATCCCCCTCAG-3') and TLS-CHOP outer reverse (5'-GAAGGAGAAAGGCAATGACTCA-3'), and inner primer set consisted of TLS-CHOP inner forward (5'-GACAGCAGAACCAGTACAACAGCAG-3') and TLS-CHOP inner reverse (5'-GCTTTCAGGTGTGGTGATGTATGAAG-3'). The expected size of the nested PCR products for the three common types of fusion transcripts were 379 bp, 103 bp, and 412 bp for type I (exons 7-2), type II (exons 5-2), and type III (exons 8-2), respectively. The results of the nested PCR for this study exhibited type II fusion transcripts in both the typical myxoid liposarcomatous and cartilaginous areas ().