Microtubule-associated protein-2 and Class III β-tubulin are expressed in extraskeletal myxoid chondrosarcoma

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 β-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 β-tubulin was studied in extraskeletal myxoid chondrosarcomas using formalin-fixed, paraffin-embedded tissues. Cytoplasmic expressions of microtubule-associated protein-2 and Class III β-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 β-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 β-tubulin transcript. Another case was examined with immunoelectron microscopy, and immunogold particles for Class III β-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.