We describe an unusual case of primary synovial sarcoma of the kidney. A 47-year-old woman had a tumor massively replacing the right kidney. There were no primary extrarenal neoplastic lesions. Microscopically, the tumor was composed of a cellular proliferation of relatively uniform spindle-shaped cells having atypical spindle or oval nuclei arranged in fascicles with tumor necrosis, without epithelial areas. Immunohistochemically, a small number of the tumor cells were positive for epithelial markers such as cytokeratin and epithelial membrane antigen. The SYT-SSX2 fusion transcripts were detected by a reverse transcription-polymerase chain reaction (RT-PCR) using RNA extracted from formalin-fixed, paraffin-embedded tissue. ETV6-NTRK3 fusion gene transcripts that result from t(12; 15)(p13;q25), which is characteristic of cellular congenital mesoblastic nephroma, were not demonstrated. To our knowledge, this is the ninth case of primary renal synovial sarcoma. This case report indicates that synovial sarcoma should be taken into account for the differential diagnosis of renal spindle cell tumors and the molecular assay detecting the SYT-SSX fusion transcripts is useful for the final diagnosis of synovial sarcoma arising in an unusual location.

Extraskeletal myxoid chondrosarcoma is a rare soft tissue sarcoma of uncertain histogenetic origin. Because recent reports have indicated neural-neuroendocrine differentiation in some extraskeletal myxoid chondrosarcomas, we investigated 25 tumors for expressions of microtubule-associated protein-2 and Class III ␤-tubulin, which are major components of microtubules and specifically localized in neurons and their derivatives. Immunohistochemical expression of microtubule-associated protein-2 and Class III ␤-tubulin was studied in extraskeletal myxoid chondrosarcomas using formalin-fixed, paraffin-embedded tissues. Cytoplasmic expressions of microtubule-associated protein-2 and Class III ␤-tubulin were detected in 21 (84%) and 13 (52%) of the 25 extraskeletal myxoid chondrosarcomas, respectively, although the number of positively stained tumor cells varied. Expression of the Class III ␤-tubulin gene was also assessed in two immunohistochemically positive cases by in situ hybridization using an oligonucleotide probe specific for its transcript, and both cases showed expression of Class III ␤-tubulin transcript.Another case was examined with immunoelectron microscopy, and immunogold particles for Class III ␤-tubulin were localized to microtubular aggregates. Our data indicate that microtubules in extraskeletal myxoid chondrosarcoma are similar to those found in neurons, further supporting the concept that neural-neuroendocrine differentiation occurs in a significant number of extraskeletal myxoid chondrosarcoma. Extraskeletal myxoid chondrosarcoma is a rare soft tissue sarcoma with distinct clinicopathologic and cytogenetical features (1-8). It is typically myxoid and arises in the deep soft tissue of the proximal extremities and limb girdles of middle-aged adults (1-4). Characteristic chromosomal translocations including t(9;22)(q22;q12), resulting in a fusion of the EWS gene at 22q12 and the CHN/TEC gene at 9q22, have been reported in extraskeletal myxoid chondrosarcoma, as well as two other less common rearrangements, including fusion of the EWSrelated gene TAF2N to CHN/TEC and fusion of the NH2-terminal domain of the basic helix-loop-helix protein TCF12 to CHN/TEC (5-8). Extraskeletal myxoid chondrosarcoma has generally been regarded as a chondroid tumor because of morphologic similarities between extraskeletal myxoid chondrosarcoma and embryonic chondrogenesis, the presence of chondroitin-4 and 6-sulfate in its myxoid matrix, frequent S-100 protein positivity, and Type II collagen synthesis by tumor cells (1, KEY WORDS: Extraskeletal

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