PMC9950734_01
(A) PET/CT of the patient showing medium FDG uptake of the left hilar and mediastinum nodes. Pre (B) and post (C) contrast sagittal T1 weighted magnetic resonance images of the right thigh of the patient, showing a deep-seated lobulated mass, with cystic regions, bleeding elements and strong heterogeneous enhancement indicative of synovial sarcoma.
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On a PET/CT examination performed approximately 1 year after radiotherapy, medium FDG uptake in the lymph nodes of the mediastinum was observed and was considered indicative of residual disease (Figure 1A). Thigh MRI revealed a (10 x 8.5) cm2 lobulated mass, situated deep in the posterior compartment with cystic regions, bleeding elements, fluid-fluid levels, and post contrast administration strong heterogeneous enhancement (Figures 1B, C).
Representative histological images from the biopsy specimen. Low (40x) (A) and high (400x) (B) power views showing solid and acinar growth pattern, poor differentiation, eosin - hematoxylin stain.
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Histologic examination revealed a neoplastic population of high cellularity, poorly differentiated with a pseudogladular and focally solid growth pattern (Figure 2).
High power views of the histological images, showing strong nuclear positivity for TLE-1 (A), strong positivity against pancytokeratin (B) and, finally, strong immunoreactivity for thyroglobulin proving the origin from the thyroid gland (C). Immunohistochemical peroxidase staining, diaminobenzidine as chromogen.
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AE1/AE3 and negative for the markers S100, CD34 and MyoD1, supporting the diagnosis of synovial sarcoma (Figures 3A, B). A molecular examination for synovial sarcoma was also requested. Hence further immunohistochemistry examination was performed using additional stains, revealing a thyroid transcription factor 1 and thyroglobulin-positive cells, suggestive of a metastatic tumor originating from thyroid tissue (Figure 3C).