FIGURE 3: A , H&E image of EHE with plump neoplastic atypical
vascular endothelial cells (inset 1, arrow) compared to admixed normal
benign flattened and spindle endothelial cells (inset 2, star).B. CD31 immunostain highlighting membranes of neoplastic cells.
C, FLI-1 immunostain highlighting large irregular nuclei of neoplastic
cells. A horseradish peroxidase-diaminobenzidine (HRPO-DAB) detection
system was used. Original magnification of A-C (400x).
A wide panel of antibodies was employed to further characterise this
lesion. CD34, CD31 and FLI-1 immunopositivity confirmed vascular
endothelial origin. Metastatic carcinoma was ruled out by negative
staining for AE1/AE3 and Cam5.2 (cytokeratins). In light of thyroid
nodule, additional TTF-1 and PAX8 stains were employed to rule out
metastatic PTC; these were both negative. They are crucial for thyroid
organogenesis and differentiation and are thus invariably positive in
the presence of thyroid metastasis9. Less likely
entities such as epithelioid sarcoma and haemangioblastoma were excluded
by negative immunostaining results for INI-1 and inhibin, respectively.
As the lesion showed well-formed vessels as opposed to the more classic
blister cells and myxohyaline stroma, a TFE3 antibody was employed to
assess for the presence of a YAP1-TFE3 gene fusion which is
characteristic in this subset of EHE. The TFE3 results were,
unfortunately negative.
There is no locally available FISH platform to assess the presence of
the WWTR1-CAMTA1 gene fusion nor is there a locally available fusion
specific antibody.
Overall the architectural, cytomorphological atypia and
immunohistochemical features are that of an atypical vascular lesion.
The features are more atypical than that haemangioma but fall short of
the significant atypia of angiosarcoma. Therefore a consensus diagnosis
of EHE was reached.