Diffuse-Type Tenosynovial Giant Cell Tumour Involving Bone Masquerading as Langerhans Cell Histiocytosis

Figure 2

(a) Needle biopsy of cuboid lesion showed clusters and cords of pinkish epithelioid cells in a fibromyxoid stroma (H&E x40). The insert showed numerous CD1a-positive cells on immunohistochemistry (IHC x40). (b) The curettage specimen showed cellular clusters of pinkish epithelioid cells with open nuclei (H&E x400). (c) Majority of epithelioid cells are Langerin-positive Langerhans cells (IHC x400). (d) Scattered cells are Clusterin-positive tumour cells (IHC x400). (e) FISH showed scattered nuclei with break-apart green and red signals of CSF-1 (arrowed).

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