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Is Anti–h-Caldesmon Useful for Distinguishing Smooth Muscle and Myofibroblastic Tumors?

Katherine M. Ceballos MD, Gunnlaugur P. Nielsen MD, Martin K. Selig BA, John X. O’Connell MB, FRCPC
DOI: http://dx.doi.org/10.1309/K5JP-A9EN-UWN7-B5GG 746-753 First published online: 1 November 2000


Misinterpretation of positive staining of antibodies to desmin, smooth muscle actin, and muscle actin as representing smooth muscle differentiation in the context of a spindle cell tumor is not uncommon. Anti–h-caldesmon is a promising novel immunohistochemical reagent for more specific smooth muscle differentiation. We studied 72 tumors (11 leiomyosarcomas, 26 malignant fibrous histiocytomas [MFHs], 11 fibromatoses, 11 cellular cutaneous fibrous histiocytomas [CCFHs], 5 malignant peripheral nerve sheath tumors, 4 synovial sarcomas, and 4 cases of nodular fasciitis), the reactive myofibroblastic response in 5 cases of acute cholecystitis, and the desmoplastic response surrounding 5 invasive breast carcinomas. Tissues were examined for expression of h-caldesmon, desmin, smooth muscle actin, and muscle actin. Diffuse staining for h-caldesmon was present only within the leiomyosarcomas. Focal staining for h-caldesmon involving less than 1% of lesional cells was present in 3 of 26 MFHs and 1 of 11 CCFHs. There was overlap in staining for the other “myoid” markers in all of the lesions that contained myofibroblasts. Anti–hcaldesmon seems to be a reliable marker of smooth muscle differentiation, and its inclusion in a panel of myoid immunohistochemical reagents should allow distinction of smooth muscle and myofibroblastic tumors.

Key Words:
  • h-Caldesmon
  • Immunohistochemistry
  • Myofibroblast
  • Smooth muscle