title: Primary renal myxofibrosarcoma.
abstract: Kidney sarcomas are rare, representing only 1% of malignant renal tumors. We herein report the case of a 70-year-old woman that was admitted for an episode of confusion in relation to hypertensive encephalopathy. Imaging investigations revealed a large mass in the right kidney with extension to the renal hilum. The patient underwent right open radical nephrectomy. The histopathologic study disclosed a 15-cm, myxoid and cellular, pleomorphic tumor with elongated, curvilinear, thin-walled vessels, and focal necrosis that involved the upper and middle segments of the kidney. Immunohistochemically, the tumor cells showed strong positivity for vimentin, bcl2 protein (nuclear staining pattern), CD34, CD99, and alpha-methylacyl coenzyme A racemase. The tumor was diagnosed as myxofibrosarcoma (MFS) grade 2 according to the FNCLCC system. To the best of our knowledge, this is the first report of an MFS arising from the kidney. Thus, MFS is an uncommon soft tissue tumor that can exceptionally arise from the kidney. The differential diagnosis with other myxoid tumors is of vital importance because it includes lesions with subtle differences and extremely variable biological behavior. Radical surgery is the treatment of choice. Long-term follow-up is recommended because of the tumor's capability for local recurrence and distant metastasis.
authors.affiliation: Department of Anatomical Pathology, Marqués de Valdecilla University Hospital, Medical Faculty, University of Cantabria and IDIVAL, Santander, Spain. Electronic address: apavbj@humv.es.
authors.forename: José-Fernando
authors.initials: JF
authors.lastname: Val-Bernal
authors.affiliation: Service of Anatomical Pathology, Doctor Negrín University Hospital, Las Palmas de Gran Canaria, Spain.
authors.forename: M Rosa
authors.initials: MR
authors.lastname: García-González
authors.affiliation: Department of Anatomical Pathology, Marqués de Valdecilla University Hospital, Medical Faculty, University of Cantabria and IDIVAL, Santander, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Mayorga
authors.affiliation: Service of Urology, Doctor Negrín University Hospital, Las Palmas de Gran Canaria, Spain.
authors.forename: Reinaldo H
authors.initials: RH
authors.lastname: Marrero
authors.affiliation: Service of Urology, Doctor Negrín University Hospital, Las Palmas de Gran Canaria, Spain.
authors.forename: Nicolás
authors.initials: N
authors.lastname: Jorge-Pérez
mesh_terms: D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D005354:Fibrosarcoma / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis / Q000473:pathology*; D009362:Neoplasm Metastasis; D009392:Nephrectomy / Q000379:methods; D012008:Recurrence
keywords: Immunohistochemistry; Kidney; Myxofibrosarcoma; Sarcoma