How does a periapical cyst differ from a periapical granuloma in structure?

• A. A periapical cyst is a fluid-filled cavity lined with epithelium, whereas a granuloma is chronic inflammatory tissue without such a lining.
• B. A granuloma has an epithelial lining; a cyst does not.
• C. Both are identical; there is no difference.
• D. A cyst is always benign; a granuloma is malignant.

Answer: (A)

Periapical cysts and periapical granulomas differ by their structural makeup: a cyst is a defined fluid-filled cavity lined with epithelium, while a granuloma is solid chronic inflammatory tissue without such an epithelial lining. The epithelial lining of the cyst creates a true cavity, often containing fluid or debris, whereas the granuloma is composed of inflammatory cells, fibroblasts, and granulation tissue at the apex without a surrounding epithelial boundary. This is why describing a cyst as a fluid-filled cavity lined by epithelium and a granuloma as tissue lacking that lining accurately captures their fundamental difference. The ideas that a granuloma has an epithelial lining or that the two are identical are incorrect, and both entities are not malignant.