[94] p63 Immunohistochemistry Is a Useful Marker for Muscle Differentiation

SE Martin, MP Gohen, TM Ulbright, EM Hattab. Indiana University School of Medicine, Indianapolis, IN

Background: p63, a member of the p53 gene family, is a selective nuclear marker of myoepithelial cells. Antibody against p63 is frequently used in the diagnosis of prostate carcinoma, as well as in the identification of myoepithelial cells in other tissues including the breast. p63 has also been shown to be expressed in squamous cell carcinoma, metaplastic breast carcinoma, sarcomatoid carcinoma, and giant cell tumor of bone. Recently, it was found that all p53 family members are involved in regulating the process of muscle differentiation through the retinoblastoma protein. Ablation of these p53 family functions blocks the differentiation program and promotes malignant transformation by enabling cooperating oncogenes to transform myoblasts.
Design: Immunohistochemical staining for p63 was performed on paraffin sections of 35 rhabdomyosarcomas, 5 leiomyomas, 5 leiomyosarcomas, 5 rhabdomyomas, 5 rhabdomyomatous Wilms' tumors, 3 cases of normal cardiac muscle and 1 medullomyoblastoma. Each case was also stained with desmin and myogenin for comparison purposes. Unlike the nuclear staining scored in myoepithelial cells, only cytoplasmic staining for p63 was considered positive.
Results: Thirty-four of 35 cases of rhabdomyosarcoma showed cytoplasmic p63 staining. Thirteen of these cases displayed exquisite definition of the cross-striations. In addition, 5/5 cases of rhabdomyoma, 5/5 cases of rhabdomyomatous Wilms' tumor, and 1/1 case of medullomyoblastoma exhibited cytoplasmic p63 staining. Cardiac muscle samples (3/3) also demonstrated positive cytoplasmic staining and distinct cross striations. Smooth muscle tumors exhibited only very focal and faint cytoplasmic staining in 5/5 leiomyomas and 4/5 leiomyosarcomas. p63 cytoplasmic staining was more intense and highlighted the cross striations with superior definition than desmin.
Conclusions: The p63 immunostain is a sensitive marker for skeletal muscle differentiation and highlights the cross-striations of strap cells with exceptional definition, far superior to desmin. p63 appears to localize to the Z bands of skeletal and cardiac muscle, while smooth muscle, which lacks cross-striations, does not stain as intensely. Ultrastructural immunohistochemical examination of p63 stained sections to aid in protein localization is underway.
Category: Bone & Soft Tissue

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 3, Tuesday Morning


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