Malignant peripheral nerve sheath tumor in an elderly patient with superficial spreading melanoma: A case report

Figure 1 Color Doppler ultrasonography findings. Color Doppler ultrasonography revealed an ill-defined hypoechoic mass in the subcutaneous soft tissues of the medial left knee with abundant dotted and band-shaped blood flow signals in and around the lesion.

Figure 2 Axial computed tomography image. The axial computed tomography image revealed that the oval well-defined lesion (orange arrows) on the medial side of the left knee had a lower computed tomography value (34 HU) than adjacent anatomical structures (62 HU), which were compressed and displaced.

Figure 3 Magnetic resonance images of the malignant peripheral nerve sheath tumor. A: The sagittal T1-weighted images of the left knee showed a heterogeneously hypointense mass (orange arrows), with an irregular shape, clear boundary, internal lobules and the absence of a visible entering or exiting nerve; B: The lesion (white arrows) showed heterogeneous hypointensity on the fat-saturated T2-weighted images and the hyperintense grid-like fascia (orange arrows) suggested peritumoral edema; C and D: The lesion with thickened skin (orange arrows) also showed heterogeneous enhancement with non-enhanced focal areas (orange arrowheads) on contrast-enhanced T1-weighted images in the sagittal and coronal plane.

Figure 4 Postoperative pathological examination. A: Hematoxylin-eosin staining photomicrograph (original magnification × 200) of the mass showed tightly packed spindle cells; B: Immunofluorescence examination (original magnification × 200) demonstrated S100 positivity on immunohistochemical analysis.