Psammoma bodies
Summary
Psammoma bodies are concentrically laminated, calcified structures found in certain neoplasms and some normal tissues. They are pathognomonic findings in papillary thyroid carcinoma, meningioma, papillary serous ovarian carcinoma, and malignant mesothelioma (remember: 'PMOM' mnemonic).
Detail
Psammoma bodies are spherical, calcified concretions measuring 10-100 micrometers in diameter, characterized by concentric laminations resembling tree rings. They form through dystrophic calcification of necrotic cells within papillary structures or around blood vessels. The pathogenesis involves initial cellular necrosis followed by calcium phosphate deposition and subsequent layered mineralization. While not exclusive to malignancy, psammoma bodies are highly characteristic of specific tumor types: papillary thyroid carcinoma (most common association, found in 40-50% of cases), meningioma (particularly psammomatous subtype), serous papillary ovarian carcinoma, and malignant pleural mesothelioma. They can occasionally be found in benign conditions like chronic inflammation or normal aging tissues. Histologically, they appear as pink-purple, concentrically laminated structures on H&E staining. Their presence aids in differential diagnosis, particularly distinguishing papillary thyroid carcinoma from follicular carcinoma, and identifying serous from other ovarian carcinoma subtypes.
Sources
- Robbins and Cotran Pathologic Basis of Disease
- Rosai and Ackerman's Surgical Pathology
- WHO Classification of Tumours series
- First Aid for the USMLE Step 1
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