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Dermatofibrosarcoma protuberans-fibrosarcomatous variant

Case contributed by Ammar Ashraf
Diagnosis certain

Presentation

Left lower abdominal mass for 25 years. Increasing in size and bulging out for the last 6 months. Also history of blood and serous discharge for the last 6 months. No history of fever, anorexia or weight loss.

Patient Data

Age: 45 years
Gender: Female

A sizable, lobulated exophytic soft tissue mass, measuring 6.3 x 5.5 x 5.4 cm, arising from the skin/subcutaneous tissues, is seen in the left iliac fossa region. Mild heterogeneous enhancement is seen in its basal part on the post-contrast scan. Surrounding skin is mildly thickened. No deep extension to the underlying anterior abdominal wall muscles or the abdominal cavity. Enlarged liver (18 cm) without any focal lesion or biliary dilatation. Enlarged spleen (15.8 cm) in its longitudinal diameter showing at least three rounded focal lesions which are hypodense on the venous phase and isodense on pre-contrast & delayed phase scans. Dilated portal and splenic veins measuring 1.8 cm and 1.5 cm respectively; however, they are patent and have no internal filling defects. Multiple enlarged intra-abdominal lymph nodes (perisplenic, porta hepatic, para-aortic, aorto-caval, common iliac and mesenteric). Many of these enlarged lymph nodes are faintly calcified. Persistent fetal lobulation seen in both kidneys. Surgical sutures seen along the lower rectum. Small simple right ovarian cyst. Mild divarication of the recti muscles noted at the level of umbilicus. 

Case Discussion

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. 

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