Encyclopedia of Pathology

Living Edition
| Editors: J.H.J.M. van Krieken

Undifferentiated Pleomorphic Sarcoma

  • Alessandro FranchiEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-28845-1_4964-1



Undifferentiated pleomorphic sarcoma (UPS) is a malignant mesenchymal tumor with no identifiable line of differentiation. It is a therefore diagnosis of exclusion.

Clinical Features

  • Incidence

    UPS originating in the genitourinary tract is rare, and literature consists mainly of single case reports.

  • Age

    UPS is a tumor of adults, arising mainly in patients between the fifth and the eight decades.

  • Sex

    It occurs predominantly in males.

  • Site

    Genitourinary UPS arises more frequently in the urinary bladder, but few examples have also been reported in the kidney, the prostate, and the spermatic cord (Kunze et al. 1994; Kulmala et al. 1994; Ptochos et al. 1999; Demir et al. 2012).

  • Treatment

    Treatment is surgical, combined in some cases with chemotherapy and radiation.

  • Outcome

    UPS is an aggressive tumor with frequent local and distant relapse and a poor prognosis.


UPS usually appears as a large multilobulated gray-white, fleshy mass. The cut surface often shows hemorrhagic, myxoid, and/or necrotic changes.


The tumor is composed by an admixture of spindle and pleomorphic cells, set in a variably collagenized, sometimes focally myxoid, extracellular matrix (Fig. 1). Tumor cells are organized in fascicular and cartwheel (storiform) patterns. Cellularity is variable, and pleomorphism, atypical mitoses, areas of tumor necrosis, histiocyte-like cells, and foamy cells, as well as giant tumor cells with enlarged, polylobulated nuclei, are commonly observed.
Fig. 1

Undifferentiated pleomorphic sarcoma presenting with a fascicular storiform pattern. Tumor cells are mainly spindled and present nuclear atypia


Immunohistochemically, tumor cells are positive for vimentin and focally for smooth muscle actin. H-caldesmon, desmin, S100 protein, and epithelial markers are usually not expressed.

Molecular Features

UPS presents complex genomic aberrations.

Differential Diagnosis

UPS can be diagnosed after having excluded other high-grade spindle and pleomorphic malignancies. The main differential diagnosis in the urogenital tract is with sarcomatoid carcinoma (de Peralta-Venturina et al. 2001), which presents morphologic and immunohistochemical overlaps with UPS (positivity for vimentin and focal expression of actin). However, sarcomatoid carcinoma presents an epithelial component, or, even in absence, it is at least focally immunoreactive to cytokeratin and/or EMA. Other high-grade pleomorphic sarcomas can be excluded by searching for specific lines of differentiation, also with the help of an appropriate immunohistochemical panel.

References and Further Reading

  1. de Peralta-Venturina, M., Moch, H., Amin, M., Tamboli, P., Hailemariam, S., Mihatsch, M., Javidan, J., Stricker, H., Ro, J. Y., & Amin, M. B. (2001). Sarcomatoid differentiation in renal cell carcinoma: A study of 101 cases. The American Journal of Surgical Pathology, 25, 275–284.CrossRefGoogle Scholar
  2. Demir, L., Can, A., Dirican, A., Bayoğlu, V., Rezanko, T. A., Akyol, M., Kucukzeybek, Y., Erten, C., & Tarhan, M. O. (2012). Malignant fibrous histiocytoma of the spermatic cord in a patient with polycystic kidney disease; review of the literature. Clinical Genitourinary Cancer, 10, 280–283.CrossRefGoogle Scholar
  3. Kulmala, R. V., Seppanen, J. H., Vaajalahti, P. J., et al. (1994). Malignant fibrous histiocytoma of the prostate. Case report. Scandinavian Journal of Urology and Nephrology, 28, 429–431.CrossRefGoogle Scholar
  4. Kunze, E., Theuring, F., & Kruger, G. (1994). Primary mesenchymal tumors of the urinary bladder. A histological and immunohistochemical study of 30 cases. Pathology, Research and Practice, 190, 311–332.CrossRefGoogle Scholar
  5. Ptochos, A., Karydas, G., Iosifidis, N., Tyrothoulakis, E., Papazafiriou, G., & Kehagia-Koutoufari, T. (1999). Primary renal malignant fibrous histiocytoma. A case report and review of the literature. Urologia Internationalis, 63, 261–264.CrossRefGoogle Scholar

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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Department of Translational Research and of New Technologies in Medicine and SurgeryUniversity of PisaPisaItaly