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Pathology · single question

What is the key HISTOLOGICAL difference between a periapical cyst and a periapical granuloma?

  1. The granuloma has a fibrous capsule; the cyst does not
  2. The cyst has an epithelial lining derived from the rests of Malassez; the granuloma does not
  3. The cyst is composed of granulation tissue; the granuloma is not
  4. The granuloma contains cholesterol clefts; the cyst never does
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Correct answer: B. The cyst has an epithelial lining derived from the rests of Malassez; the granuloma does not

  • A. Both lesions typically have a peripheral fibrous connective tissue wall. This is not the discriminator.
  • B. CORRECT. The single defining difference is EPITHELIUM. A periapical (radicular) CYST has a lumen lined by stratified squamous EPITHELIUM, proliferated from the epithelial RESTS OF MALASSEZ under chronic inflammatory stimulus. A periapical GRANULOMA is chronically inflamed granulation tissue — lymphocytes, plasma cells, macrophages, fibroblasts and capillaries — with NO epithelial lining. Radiographs cannot reliably distinguish them; only histopathology can.
  • C. This reverses the terms. Both contain inflamed granulation tissue; the cyst additionally has an epithelial lining and a lumen.
  • D. Cholesterol clefts with associated multinucleated giant cells can be present in BOTH lesions and are not discriminatory.

Note: Despite the name, a periapical granuloma is NOT a true granuloma — there is no epithelioid histiocyte formation. It is simply chronic granulation tissue, and the name is a historical misnomer.

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