Specificity and sensitivity of differentiation antigens in superficial soft tissue tumors: comparison of SMA, calponin, H-caldesmon, C-kit, PLAP and HPL.

We examined the expression pattern of smooth muscle actin (SMA), h-caldesmon (HCD), calponin (CALP), placental alkaline phosphatase (PLAP) and human placental lactogen (HPL) in benign and malignant spindle cell superficial soft tissue tumors in order to determine the role of these markers in differential diagnosis. Archival tissue from 38 patients with superficial smooth muscle cell and so-called fibrohistiocytic tumors (8 benign fibrous histiocytomas (BFHs), 6 dermatofibrosarcoma protuberans (DFPT), 9 malignant fibrous histiocytomas (MFHs), 9 leiomyomas (LMs) and 6 leiomyosarcomas (LMSs)) were immunostained with antibodies against SMA, HCD, CALP, PLAP and HPL. smooth muscle cell (SMC) tumors showed significantly high immunopositivity for HCD than that of so-called fibrohistiocytic tumors (p is less than or equal to 0.05) but 1/3 of DFPT and MFH cases and half of BFH cases also showed HCD immunopositivity; thus, this difference is debatable and not highly discriminative as expected. All tumor groups showed 100% immunopositivity for CALP. SMC tumors displayed significantly stronger and more widespread immunostaining pattern for PLAP than so-called fibrohistiocytic tumors (p < 0.05). Superficial soft tissue tumors did not express c-kit. In conclusion, HCD and PLAP can be used as ancillary immunomarkers in differential diagnosis of SMC tumors (Tab. 2, Fig. 7, Ref. 37).