Celiac Disease Marsh 3B Villous Atrophy

A 28-year-old woman presents with a 2-year history of chronic bulky, pale, foul-smelling diarrhea, 8 kg weight loss, abdominal bloating, and iron-deficiency anemia. She has secondary amenorrhea, an itchy vesicular rash on extensor elbows and knees (dermatitis herpetiformis), and angular stomatitis. Serology shows markedly elevated IgA anti-tissue transglutaminase antibody (12× upper limit of normal), positive endomysial antibody, and HLA-DQ2 positivity. Upper gastrointestinal endoscopy of the duodenum is performed. The structure marked **B** in the diagram—showing loss of duodenal folds with mosaic (fissured), nodular, and scalloped mucosa in the second part of duodenum—is consistent with which histopathological finding on duodenal biopsy?