Presentation of a Rare Malignancy: Leiomyosarcoma of the Prostate
Diagnosis
Diagnosis may be further eluded as digital rectal exam (DRE) findings tend to reveal nonspecific enlargement of the prostate, resembling that of BPH. DRE may show a hard and firm prostate with nodular induration at the base or over the lobes of the prostate.6 At this stage a urology consultation is useful, as diagnosis is most commonly achieved using transrectal ultrasound (TRUS) with ultrasound-guided needle biopsy or after a TURP procedure.3
Prostate sarcoma is associated with markedly enlarged prostate volume, irregular margins with invasion, or heterogenous hypoechoic lesions on TRUS.7 Transperineal biopsy, computed tomography (CT)-guided biopsy, or suprapubic prostatectomy have been less frequently employed for diagnosis in previously reported cases.8 Specialized imaging modalities, such as CT scan or bone scan, do not show any specific findings with regards to these tumors; their role is limited to evaluation of the local and distant metastasis and for follow-up assessments.9 Transabdominal ultrasound may assess hydronephrosis or enlarged prostate and its relation to nearby structures, although it has not been shown to be helpful in establishing a specific diagnosis.6
Histologically, prostatic leiomyosarcoma is a distinct subtype of prostatic sarcoma. Other subtypes include stromal tumors such as rhabdomyosarcoma, fibrosarcoma, and spindle cell sarcoma.2 The majority of leiomyosarcomas are high-grade lesions demonstrating neoplastic spindle cells with nuclear atypia, multifocal necrosis, and cystic degeneration. Low-grade leiomyosarcomas are very rare.10 Immunohistochemistry is characteristically positive for vimentin, smooth muscle actin, and desmin expression. Cytokeratin may be positive in up to 25% of cases, whereas S-100, CD34, CD117, and PSA are negative.2,3 These histopathological findings help to differentiate leiomyosarcoma from other prostatic tumors.
Tumor size may vary greatly, and measurements have been reported to range from 3 cm to 21 cm, frequently presenting with invasion of local structures.11 Advanced stage disease is commonly found at initial diagnosis and is thought to be due to the lack of early specific symptoms. Metastatic disease at presentation may be found in up to one-third of patients, with the lungs being the most common site of metastasis followed by the liver. Local extent and distant spread of disease may be determined by CT or magnetic resonance imaging (MRI) scans, which provide clear delineation of neoplastic and nonneoplastic tissues. 
Treatment
Treatment regimens may include a multimodal approach of combination surgery, radiation, and chemotherapy. However, there are currently no standardized guidelines for treatment and the optimal therapy remains unknown.2,3,6 Surgery remains the mainstay of treatment, and patients with surgically resectable tumors are treated with curative intent. Surgeries performed include radical retropubic prostatectomy, radical cystoprostatectomy, suprapubic prostatectomy, and pelvic exenteration.2,5,8,12 These operations may be preceded or followed by radiation therapy and/or chemotherapy depending on extent of disease.
