A Case of Malignant Rhabdoid Tumor Arising from Soft Parts in the Prepubic Region

Abstract
An extrarenal malignant rhabdoid tumor arising from soft parts in the prepubic region of a 37-year-old man is described. This case appears to be unusual with regard to its location and age at onset. To our knowledge, the patient is the oldest recorded in whom such a lesion has arisen. Histologically, the tumor consisted of an admixture of polygonal and elongated cells with abundant eosinophilic cytoplasm frequently containing hyaline-like globules. Ultrastructurally, these cytoplasmic inclusions were compatible with intermediate filaments. Immunohistochemical staining disclosed keratin (non-squamous epithelial type) and epithelial membrane antigen positivity. These characteristic features were identical to malignant rhabdoid tumor of the kidney seen in infants and young children. This extrarenal malignant rhabdoid tumor showed an aggressive clinical course, although its exact histogenesis was unclear.