Ossifying fibromyxoid tumor of the soft tissue in the left upper arm and a review of the literature: A case report

Abstract

Ossifying fibromyxoid tumor (OFMT) of the soft parts is a mesenchymal neoplasm of uncertain lineage. Fibromyxoid matrix and peripheral metaplastic bone are common histological features of this type of tumor. In the present study, a case of OFMT in a 33-year-old female was reported. The patient was referred to the First Affiliated Hospital of China Medical University (Shenyan, China) in January 2018. The patient had developed a mass in the left upper arm 6 months prior to presentation, which was slowly enlarging. The tumor was 1.5 cm in diameter, with hard texture. Histologically, the tumor showed a clear boundary with no invasion into the adjacent tissue. The majority of tumor cells were round and medium-sized, with abundant pale cytoplasm, without obvious atypia and densely arranged in sheets. The tumor tissue was characterized by cartilage-like morphology and fibromyxoid and hyalinization matrix. Mitotic index was <1/10 high-power fields. Additionally, tumor cells were positive for S-100 and vimentin expression, but negative for smooth muscle actin, CD34, cytokeratin, desmin, human melanoma black 45 and melanoma A. Ki67 index was ~1%. The patient underwent surgery and the tumor was totally removed. No recurrence was observed at the final 6-year follow-up. Based on the aforementioned findings, the patient was diagnosed as typical OFMT. Slow growth and clear boundaries often suggest an indolent nature to this type of tumor. However, close follow-up should be performed due to its malignant potential.

Keywords: case report; ossifying fibromyxoid tumor; upper arm.

Figure 1

Ultrasound examination of the tumor. Ultrasound examination of the tumor. Tumor located 3 mm below the epidermis in the left upper arm (blue arrow) measuring 18x12 mm. The boundary of the mass was clear. The shape was regular and nearly ellipsoidal. No significant blood flow signal was detected. The patient underwent surgery and the tumor was completely removed. No tumor recurrence was observed at 6 years after surgery.

Figure 2

Histopathological features of the tumor. (A) Boundary of the tumor was clear (black arrows; magnification, x100). (B) Fibrous capsule (red arrowhead) surrounding the tumor tissue. (C) Tumor cells were dense and the majority were arranged in sheets. Mucous matrix was seen in some areas. (D) Some areas displayed cartilage-like features (area in the box). Magnification, x200 and (E) x400. (F) Cells with pericellular lacune-like structures (arrow; magnification, x400). (G) In some areas, cells were spindle-shaped with mucoid matrix. (H) Some areas showed hyalinization matrix. Magnification, x40. (I) Tumor cells were mostly round, medium-sized with plump pale cytoplasm. Tumor cell nuclei were round or oval and light-stained (magnification, x400). Mitotic index was <1/10 high-power fields.

Figure 3

Immunohistochemical findings. Tumor cells were negative for (A) smooth muscle actin (B) CD34, (C) creatine kinase, (D) desmin, (E) human melanoma black 45 and (G) melanoma A. Positive immunostaining for smooth muscle actin and CD34 was detected in the blood vessels in tumor tissues (black arrows). (F) Ki67 immunostaining was seen in the nucleus. Ki67 index was ~1 and 5% in certain areas. (H) Weakly positive S-100 staining is shown. (I) Vimentin was diffusely positive. Magnification, x200.