RESUMO
Purpose To investigate the clinicopathological characteristics and differential diagnosis of spindle cell rhabdomyosarcoma ( SCRM) . Methods Three cases of SCRMs were analyzed by gross examination, microscopy and immunohistochemistry. Relevant lit-eratures were reviewed to summarize the diagnostic features of SCRM and its differential diagnosis. Results All the 3 cases were male infants aged from 2 days to 4 years. 2 cases were located in paratesticular and 1 in back. Tumors were all well-circumscribed but unen-capsulated, with white-gray cut surface, firmed and sized 2. 0 to 6. 0 cm in diameter. Histologically, tumors displayed invasive growth but were well-circumscribed. Tumor cells were spindle to round with eosinophilic cytoplasm and fascicular, storiform, wavy appear-ance. Horizontal structure and striated muscle brood cells were observed in some cells or local regions. A small amount of collagen fi-brils were observed in the mesenchymal components. The nucleus were long or fine wavy with unconspicuous nuclear atypia, mitosis could be occasional observed. Immunohistochemically, tumor cells were positive for vimentin, desmin, myogenin and MyoD1. CK,α-inhabin, AFP, CD34 and S-100 were negative. Conclusions SCRM is a rare and new type of rhabdomyosarcoma that commonly oc-curred in infant. It should be differentiated from other tumors, such as infantile fibromatosis, congenital fibrosarcoma, fibrosarcoma, leiomyosarcoma, triton tumor, malignant melanoma of promoting the fibrous tissues.