Procedure: Excisional biopsy of pedunculated skin mass.

Gross description: Specimen submitted in one container, in formalin, labeled "abdominal mass", and consists of a skin fragment measuring 10 x 5 x 3 cm showing polypoid ulcerated mass measuring 7 x 6 x 4 cm.  At the cut section, multinodular ill-defined, firm whitish ad whorled lesion is identified measuring 6.5 x 6 x 3.5 cm. The skin lesion is at 1 cm away from the lateral margin and at 2.5 cm from the deeper margin.  

Microscopy: Extensive sub epidermal proliferation of spindle cells interlacing among fibrous stroma with infiltrative borders extending into the surrounding adipose tissue. Multiple foci of transition into more storiform and peripheral palisading patterns along with nuclear atypia and brisk mitotic activity of 5-6/10 HPF (high power field). No necrosis identified. Margins are free (tumor is located at 1 cm away from the closest lateral margin and 2.5 cm from the closest deeper margin). Nuclear atypia and brisk mitoses (6 mitoses per 10HPF). The immunohistochemistry: CD34: Positive in some peripheral areas of the tumor but weak or negative in the center of the tumor. Desmin: Negative. h-Caldesmon: Negative. SMA: Negative. S100: Negative. The tumor's analysis with Next-generation sequencing (NGS) was unsuccessful due to technical issues.

Diagnosis: High grade fibrosarcomatous variant of dermatofibrosarcoma protuberans (FS-DFSP) infiltrating the skin & subcutaneous tissue with superficial ulceration.

The patient was referred to the medical oncologist for further evaluation.