A 62-year-old man presents with fatigue, abdominal pain, cramping, and nausea. Physical examination is unrevealing, and a trial of conservative medical treatment does not relieve his symptoms. Computed tomographic scan of the abdomen reveals a partially obstructive 5-cm distal duodenal mass. Image-guided biopsy produces a nondiagnostic specimen, so a diagnostic laparoscopy is performed. What clinicopathologic feature favors a diagnosis of clear cell sarcoma of soft parts involving the gastrointestinal tract over a diagnosis of GNET?