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h-Caldesmon as a Specific Marker for Smooth Muscle Tumors
Comparison With Other Smooth Muscle Markers in Bone Tumors

Kazuo Watanabe MD, Takahiro Tajino MD, Miho Sekiguchi MD, Toshimitsu Suzuki MD
DOI: http://dx.doi.org/10.1309/JNQX-F4KM-Q0Q0-7XK8 663-668 First published online: 1 May 2000


Caldesmon is a protein widely distributed in smooth and non–smooth muscle cells and is thought to regulate cellular contraction. Its isoform, highmolecular- weight caldesmon (h-CD), was demonstrated to be specific for smooth muscle cells and smooth muscle tumors of the soft tissue and to never be expressed in myofibroblasts. We performed an immunohistochemical study to examine h-CD expression in the following bone tumors: conventional and nonconventional osteosarcoma, 13; malignant fibrous histiocytoma of bone, 5; giant cell tumors of bone, 5; chondroblastoma, 3; metastatic leiomyosarcoma, 2; and rhabdomyosarcoma, 1. Frequent immunoreactivity for muscle actin (alpha-smooth muscle actin or muscle-specific actin) was seen in 11 of 13 osteosarcomas and all other tumors, whereas h-CD was expressed intensely only in 2 leiomyosarcomas. h-CD is considered a specific and useful marker to distinguish smooth muscle tumor from bone tumors with myoid differentiation.

Key Words:
  • Caldesmon
  • Actin
  • Leiomyosarcoma
  • Bone tumor
  • Osteosarcoma
  • Malignant fibrous histiocytoma
  • Giant cell tumor of bone
  • Chondroblastoma