PMC6838480_01
Appearance of the initial tumor A subcutaneous mass (10 x 10 mm) in the right forearm was clinically diagnosed as nodular fasciitis.
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A 75-year-old man presented to the outpatient department with a 1 x 1 cm mass on his left forearm that had enlarged rapidly over the previous 2 weeks without specific symptoms (Fig. 1).
Comparison of the initial and recurrent tumors.. (a) MRI showed a mass (9 x 6 mm) that was thought to be nodular fasciitis.. (b) Four years later, the recurrent subcutaneous mass (23 x 10 mm) was difficult to diagnose by CT.
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Contrast computed tomography (CT) demonstrated a mass measuring 23 x 10 mm (Fig. 2).
Pathological findings of the recurrent tumor.. (a) The mass is surrounded by a well-defined fibrous capsule.. (b) The tumor cells have eosinophilic cytoplasm and polymorphic nuclei with anisokaryosis. Physaliphorous cells are sometimes seen in association with proliferation of fibroblasts and capillaries. Cells are also seen proliferating in the interstitial region or form irregular bundles in myxoid stroma. (a, b: hematoxylin-eosin stain).. (c) Immunostaining demonstrates that almost all of the tumor cells are negative for S100 protein.
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Histopathological examination revealed spindle-shaped polymorphonuclear cells with eosinophilic cytoplasm and vacuoles (Fig. 3).
Additional excision.. (a) The lateral surgical margin was set at 20 mm.. (b) The deep margin was set at the full thickness of brachioradialis muscle.. (c) Residual tumor was not detected either macroscopically or histopathologically.
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Since malignancy could not be excluded, wide resection was performed with a lateral margin of 20 mm from the previous surgical scar and partial removal of brachioradialis muscle at the deep margin (Fig. 4).