PATHOLOGY

Spindle Cell Lesions of the Adult Prostate
Hansel DE, Herawi M, Montgomery E, Epstein JI
Department of Pathology, The Johns Hopkins Hospital, Baltimore, MD, USA
Mod Pathol. 2007; 20: 148-58

• Prostatic spindle cell lesions are diagnostically challenging and encompass a broad array of benign and malignant processes. A subset of these lesions arises only within the prostate and generally represents entities that originate from the prostate epithelium or stroma, such as sclerosing adenosis, sarcomatoid carcinoma, stromal tumors of uncertain malignant potential (STUMP), and stromal sarcoma. Another subset of spindle cell tumors that involve the prostate are also found at other sites and include solitary fibrous tumor, leiomyosarcoma, and neural lesions among others. Finally, tumors may secondarily involve the prostate yet present as primary prostatic processes, as is evident with several cases of gastrointestinal stromal tumors (GIST). The utility of ancillary studies, including immunohistochemistry, is often limited and the main criteria for diagnosis are the morphologic findings by routine H&E stain. This review addresses the various entities that may present as spindle cell tumors within the adult prostate and discusses the functional aspects of the differential diagnosis of these lesions.
  
  
• Editorial Comment
  Spindle cell lesions are rare in the prostate. Among these lesions is worth commenting for the urologists sarcomatoid carcinoma and the lesions proposed by the authors to be called STUMP. There is a lot of debate in the literature about the terms sarcomatoid carcinoma vs. carcinosarcoma. These terms apply to tumors that show spindling of the cells sometimes with heterologous differentiation like osteosarcoma, condrosarcoma, angiosarcoma and others. There is a tendency to call these cases sarcomatoid carcinoma with heterologous differentiation based on studies that show a monoclonal origin for these tumors.
  Stromal tumors of uncertain malignant potential (called by the authors STUMP) encompass a group of lesions that most of the times are hard to establish histologically the biological behavior in contrast to frankly sarcomatous lesions like leiomiosarcoma, rabdomiosarcoma and others. STUMP includes several patterns of lesions originating from the specialized stroma of the prostate: phyllodes tumor of the prostate, hypercellular stroma with scattered atypical yet degenerative cells, and extensive overgrowth of hypercellular stroma with the histology of a stromal nodule (1). STUMPS are considered neoplastic, based on the observations that they may diffusely infiltrate the prostate gland and extent into adjacent tissues, and often recur. Although most cases of STUMP do not behave in an aggressive fashion, occasional cases have been documented to recur rapidly after resection and a minority has progressed to stroma sarcoma.

Reference
1. Cheville J, Algaba F, Boccon-Gibod L, Billis A, Cheng L, Epstein JI, Furusato M, Lopez-Beltran A: Mesenchymal Tumours. In: Eble JN, Sauter G, Epstein JI, Sesterhenn (eds.), Pathology & Genetics, Tumours of the Urinary System and Male Genital Organs. World Health Organization Classification of Tumours, IARC Press, Lyon, 2004.

Dr. Athanase Billis
Full-Professor of Pathology
State University of Campinas, Unicamp
Campinas, Sao Paulo, Brazil