Giant cell types: Langhans, foreign body and Touton
A giant cell is a large cell with many nuclei, formed when macrophages fuse, and the way the nuclei are arranged tells the Langhans, foreign body and Touton types apart.
Remember
Look at where the nuclei sit: at the edge, often in a horseshoe, points to Langhans; scattered at random points to foreign body; a ring around central cytoplasm, and foamy, lipid-rich cytoplasm outside the ring, points to Touton.
Macrophages are large white blood cells that arise from blood monocytes and engulf and digest material. Sometimes macrophages meet something they cannot phagocytose (engulf and digest), such as a foreign body or certain bacteria. They then fuse together into a giant cell, a large cell with many nuclei that isolates the offending substance. The type present can aid diagnosis.
In a Langhans giant cell the nuclei lie at the edge of the cell, often in a horseshoe. This type occurs in granulomatous inflammation, such as tuberculosis (TB), when macrophages cannot destroy an organism. The shape of a giant cell alone does not establish TB; the clinical context and further investigations are needed to establish the cause.
A foreign body type giant cell has nuclei arranged randomly through the cytoplasm. It forms around a foreign body, meaning inert foreign material such as suture or splinters, that macrophages cannot digest.
A Touton giant cell has its nuclei in a ring or wreath around central cytoplasm, plus foamy, lipid-rich cytoplasm outside the ring. The foamy look comes from the cell having phagocytosed lipid, so Touton cells are seen where lipid content is high, such as fat necrosis (death of fatty tissue) and xanthomas (fatty deposits made of lipid-laden cells).
The quickest clue to the type is the nuclear pattern.
Key facts
- Langhans
- nuclei at the edge of the cell, often in a horseshoe, in granulomatous inflammation including tuberculosis
- Foreign body type
- nuclei arranged randomly, around material that macrophages cannot digest
- Touton
- a ring of nuclei around central cytoplasm, plus foamy, lipid-rich cytoplasm outside the ring, seen in areas of high lipid content such as fat necrosis and xanthomas
- Why they form
- macrophages fuse when they cannot phagocytose, and the giant cell isolates the offending substance
- Tuberculosis caution
- the shape of a Langhans cell alone does not establish tuberculosis; the clinical context and further investigations are needed
Exam traps
- A foreign body giant cell does not show a horseshoe of nuclei at the edge of the cell, because its nuclei are scattered haphazardly through the cell. The horseshoe belongs to the Langhans type.
- Langhans and Touton cells both show a ring-like nuclear pattern, but a Langhans giant cell has its nuclei around the edge of the cell, often in a horseshoe, not a ring around central cytoplasm with foamy cytoplasm outside it.
- A Touton giant cell does not form around suture material, because a ring of nuclei with foamy, lipid-rich cytoplasm belongs to fatty lesions such as xanthomas and fat necrosis.
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