Leiomyosarcoma of the prostate

Leiomyosarcoma of the prostate is a rare mesenchymal smooth muscle malignancy of the prostate gland.

Epidemiology

It is a rare tumor with less than 200 cases reported in the literature accounting for approximately 25% of all sarcomas of the prostate gland and less than 0.1% of primary prostate tumors ^1-3. It has been reported in children and adults in a range from 2.5 years to 80 years but is far more frequent in adults ^1-5.

Diagnosis

The diagnosis of leiomyosarcoma of the prostate is based on histological characteristics.

Clinical presentation

Patients may complain of symptoms related to the urinary tract as urinary frequency, urgency, voiding difficulties, poor flow or urinary retention, other symptoms might include perineal or rectal pain, burning on ejaculation or weight loss. Digital rectal examination (DRE) might indicate prostatic hypertrophy or a protruding, exophytic mass ^1-4. 

A urinalysis might show microscopic or macroscopic hematuria. Prostate specific antigen (PSA) might be raised or not, but in the case of the first cannot be used to monitor the progress of the disease ^1,2.

Complications

If left untreated leiomyosarcoma of the prostate will progress as any malignancy. In addition, it will lead to the following ¹:

• urinary retention / hydronephrosis
• anemia

Pathology

Macroscopic appearance

Macroscopic features of leiomyosarcomas of the prostate are non-specific. At the time of the diagnosis, tumors are often large with a capsular breach or bladder invasion. In addition, they might show necrotic or bleeding areas especially if the median area is involved ¹. 

Microscopic appearance

Microscopically the leiomyosarcoma of the prostate gland typically features spindle cells with nuclear atypia and increased mitotic activity ^1-4. In addition, there might be necrosis and cystic degeneration ^3,4. 

Immunophenotype

Immunohistochemistry stains are usually positive for vimentin, CD44 or smooth muscle actin. A smaller amount of tumors expressed desmin or cytokeratin ^1,2.

Radiographic features

Ultrasound

Transrectal ultrasound might show the following:

• heterogeneous hypoechoic lesions
• enlargement of the prostate
• extracapsular extension
• infiltration of the bladder base
• hydronephrosis

CT

CT might show locally extensive tumors or lymphadenopathy.

MRI

MRI might show a lobular or multilobular mass sometimes with cystic or necrotic changes. Also, there might be signs of local tumor extension or regional lymphadenopathy ⁵.

• T2: low signal intensity

Radiology report

The radiological report should include a description of the following:

• tumor size and extent
• localization within the prostate gland
• signs of extracapsular extension: e.g. broad capsular contact (≥10-15 mm), capsular bulge, obliteration of the rectoprostatic angle, capsular breach, neurovascular asymmetry
• signs of seminal vesicle invasion:  direct tumor extension above the prostatic base expressed by T2w hypointensity and/or diffusion restriction
• lymph node

Treatment and prognosis

Treatment options of leiomyosarcoma of the prostate gland include radical surgery from radical prostatectomy to pelvic exenteration, chemotherapy or radiotherapy or any combination of the three ¹.

Generally, the overall prognosis of leiomyosarcoma of the prostate has been reported to be poor. Best survival rates have been reported for curative surgery with no tumor residue and no metastatic disease ¹.

History and etymology

Apparently leiomyosarcoma of the prostate has been reported in 1853 by the French physician Isambert ^1,6.

Differential diagnosis

Conditions that can mimic the presentation and/or the appearance of a leiomyosarcoma of the prostate gland include:

• prostate carcinoma
• rhabdomyosarcoma of the prostate
• nodular hyperplasia with atypia
• gastrointestinal stromal tumor of the rectum (rectal GIST)