PMC9499769_01
(a) Plain X-ray of left foot demonstrated an expansile lytic lesion in cuboid and lateral cuneiform. (b) CT scan highlighted its well-defined margin and cortical scalloping of lateral cuneiform (arrowed). (c) MRI showed PD-intermediate signal of the lobulated lesion with distal cortical perforation and (d) hyperintense signal on T2.
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Plain X-ray and CT scan (Figures 1(a) and 1(b)) showed a multilobulated expansile osteolytic lesion in the left cuboid and lateral cuneiform bones. MRI demonstrated PD-intermediate and T2-hyperintense signal in the lesion matrix (Figures 1(c) and 1(d)).
(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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Needle biopsy was done and showed tumour tissue characterized by clusters and cords of pinkish epithelioid cells in a fibromyxoid stroma (Figure 2(a)). Further IHC demonstrated numerous CD1a (Figure 2(a), insert) and Langerin-positive Langerhans cells, while H3.3G34 W and H3K36 M for giant cell tumour of bone and chondroblastoma, respectively, were negative. There were cords and clusters of pinkish epithelioid cells similar to those seen in the needle biopsy (Figure 2(b)). IHC (Figure 2(c)). In addition, there were prominent pseudoalveolar spaces, focal chondroid metaplasia, aggregates of multinucleated giant cells, and scattered Desmin-positive dendritic cells. These features were compatible with a diffuse-type tenosynovial giant cell tumour (DTSGCT), being supported by IHC for Clusterin which stained a minor population of the epithelioid cells (Figure 2(d)) and cells lining the pseudoalveoli. This diagnosis was further confirmed by fluorescent in situ hybridization (FISH) demonstrating colony stimulating factor 1 (CSF1) translocation in scattered cells using a break-apart probe (Figure 2(e)).