PMC7522039_01
USG showed a 6 x 5.3 mm round oval subcutaneous cystic lesion in the posteromedial area of the distal femoral region.
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During the USG procedure as shown in Fig. 1, the patient complained of pain, presumably due to an inflammatory process of the lesion.
CT Angiography resulted in normal muscular and skeletal structures without vascular abnormality features.
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The CT angiography in Fig. 2 revealed normal muscular and skeletal structures without vascular abnormality features.
Yellowish, firm, thin, and encapsulated tumor measuring 1.5 x 10 x 0.5 cm.
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The gross specimen was 1.5 x 10 x 0.5 cm, firm, solid, and partly cystic with yellowish-white nodules as shown in Fig. 3.
Excised Tissue Microscopic features.. (a) Finely demarcated nodules composed of small rounded cells forming syncytial structures surrounding thin capillary vessels (perivascular growth). Some empty cystic area was seen (H&E, 10x), (b) Round tumor cells with round or oval smooth nucleus, and bland chromatin (H&E, 40x), (c) Immunohistochemistry CD 31 (40x), showing vascular endothelial cells (brown). All tumor cells are negative stained thus confirmed to be non-endothelial neoplasm, (d) Immunohistochemistry Smooth Muscle Actin (SMA). All tumor cells and vascular are positive stained. SMA is a characteristic of protein in glomus cells 1-3 (20x), (e) Immunohistochemistry S100. All tumor cells are negative stained. Tumor cells are not neurogenic tumor (40x).
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The microscopic feature in Fig. 4 showed relatively well-circumscribed nodule with small dilated vascular spaces surrounded by sheets and clusters of round monomorphic glomus cells with rounded nuclei and moderated amounts of eosinophilic cytoplasm.
Smooth Muscle Actin (SMA) (40x).. All positive tumor cells are surrounded by thin capillary spaces and form.. a "perivascular collar" (marked with the arrows).
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As shown in Fig. 5, the specific smooth muscles' actin protein indicated tumor cells, while S100 for the neurogenic origin and CD 31 for the endothelial cells of the tumor cells were negative.