Low power: DQ stain
Image showing predominantly cohesive fragments of monomoporhic cells with uniform nuclear sizes and minimal cytoplasm. Note scattered single spindle cells in the background
Low power: Pap stain
Images showing fragments with transgressing vessels and scattered single monomorphous nuclei in the background. Note the absence of necrosis, marked atypia and prominent mitoses.
High power: DQ stain
Image showing slight variability in nuclear size, lack of nucleoli, small pale blue cytoplasm, eccentric nuclear location. Note the some rare very large nuclei are seen; this is reminiscent of ancient atypia noted in other neoplasms
Cell block showing fragments with artifactual trabecular arrangement. The cells are of uniform size and shape, have abundant pale pink cytoplasm, eccentrically placed nuclei, lack nucleoli, lack single cell necrosis, lack marked atypia and mitoses. In this example, the lesion was located in the left lower lobe of the lung and was thought to be atypical carcinoid by morphology alone. Special stains clinched the diagnosis of synovial sarcoma
TLE-1 immunostain is consistent with the diagnosis of synovial sarcoma in the light of the morphologic features. It is not specific for the entity; however, can be used as a surrogate marker that is representative of t(X;18).
Features
• Typically biphasic with spindled and epithelioid cells
• Monophasic synovial sarcoma has predominant spindled pattern
• Spindle cells
– Uniform bland cells
– Elongated hyperchromatic and irregular nuclei
– Conspicuous nucleoli
– Scant cytoplasm
• Epithelioid cells
– Round and regular nuclei
– Fine even chromatin
– Conspicuous nucleoli
– Moderate amount of vacuolated cytoplasm
• May have mitosis including atypical mitotic figures
• Mast cells may be present
• IHC: cytokeratin, EMA, TLE, S100 (focal), CD99, BerEp4, vimentin, calretinin
• Translocation t(X;18) SYT:SSX fusion