Fig. 1

a Operative specimen revealed a subcutaneous tumor measuring 40 × 40 mm. b Split surface of the tumor. c Histopathological examination with hematoxylin and eosin staining of the tumor showed evidence of malignant spindle-cell proliferation (× 200). d–f Immunohistochemistry showed that these tumor cells were positive for CK AE1/AE3 (d; × 400) and CK7 (e; × 400), but negative for CK20 (f; × 400)