Diagnostic Ultrasound - Abdomen and Pelvis

Focal Lesion in Prostate
994
Differential Diagnoses: Prostate
DIFFERENTIAL DIAGNOSIS
Common
• Benign Prostatic Hyperplasia (BPH) Nodules
• Prostatic Calcification
• Prostate Carcinoma (PCa)
• Atypical Small Acinar Proliferation
• Prostatic Intraepithelial Neoplasia (PIN)
• Prostatitis
• Retention Cyst
• Focal Atrophy/Fibrosis
Less Common
• Prostatic Abscess
• Müllerian Duct Cyst
• Utricle Cyst
• Seminal Vesicle Cyst
Rare but Important
• Ejaculatory Duct Cyst
• Vas Deferens Cyst
• Other Primary Prostate Neoplasms
○ Multilocular prostatic cystadenoma, sarcoma, small and
squamous cell carcinomas, stromal tumors of uncertain
malignant potential
• Secondary Tumors of Prostate
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
• Focal lesion may be discovered by digital rectal exam (DRE)
as incidental finding or part of screening
○ Or in patient with symptoms, signs, or abnormal
lab/microbiology studies
– Fever, pain, dysuria, hematospermia, painful
ejaculation, obstructive urinary symptoms
– ↑ PSA, abnormal urinalysis, UTI
• Location of cystic lesion may help in diagnosis
Helpful Clues for Common Diagnoses
• BPH Nodules
○ Enlarged gland with hyper- and hypoechoic nodules;
echogenicity dependent on composition
○ Arise in transition zone (TZ) and periurethral glands
○ ± cystic degeneration, which is common, accounts for
most cystic prostatic lesions; irregular shapes, various
sizes, may contain hemorrhage or calcification
• Prostatic Calcification
○ Often incidental finding in asymptomatic men; seen in
benign (prostatitis) and malignant (PCa) diseases;
significance is poorly understood, possibly dependent on
zonal distribution
○ Laminated bodies of secretions and desquamated cells
are called corpora amylacea → deposition of calcium
crystals → calculi
• Prostatic Carcinoma (PCa)
○ ~ 70% originate from peripheral zone (PZ)
○ Often indistinguishable from BPH nodules in TZ
○ Historically, PCa on TRUS described as hypoechoic PZ
lesion, but other nonmalignant entities (prostatitis,
atrophy, PIN) are also hypoechoic; hypoechoic lesion has
17-57% change of being cancer
○ > 30% of PCa are isoechoic
○ Due to earlier cancer detection with PSA, study showed
only 9% of hypoechoic nodules contained PCa compared
with 10% of isoechoic areas
• Atypical Small Acinar Proliferation
○ When needle biopsy shows foci that are probably PCa
but either lack definitive diagnostic features or are too
small to be certain, they do not represent edge of benign
lesion
○ If other cores are negative, rebiopsy is performed
○ ~ 40% of men diagnosed with atypia will have PCa
diagnosed on rebiopsy
• PIN
○ Prostatic glandular epithelial dysplasia
○ Management of high-grade PIN is controversial; PCa
diagnosis on rebiopsy is similar to that in men whose
initial biopsies showed normal tissue
• Prostatitis
○ Acute: Bacterial infection, E. coli is most common
causative organism; enlarged gland, but may be normal
size; global or focal hypoechogenicity; ↑ global or
perilesional vascularity
○ Chronic: Normal-sized gland; heterogeneous ± Ca++
– Chronic bacterial: Insidious onset; relapsing, recurrent
UTI due to persistent infection despite antibiotics
– Cavitary prostatitis: Fibrosis causes ductal stenoses
and acinar dilation → multiple cysts of varying sizes
throughout gland → Swiss cheese appearance
– Granulomatous prostatitis: Rare nodular form of
chronic prostatitis; mimics PCa on DRE and imaging;
may be seen after BCG therapy for bladder cancer;
diagnosis by biopsy
• Retention Cyst
○ Common; often asymptomatic; due to obstructed acini
○ Round, unilocular cyst with smooth walls; size ~ 1-2 cm;
lateral location
○ May be indistinguishable from cystic BPH nodule
Helpful Clues for Less Common Diagnoses
• Prostatic Abscess
○ Most commonly due to acute bacterial prostatitis
○ Complex fluid collection with thick walls/septa and
peripheral hyperemia ± internal debris ± gas
○ TRUS is preferred method of evaluation; can perform
aspiration for diagnosis and therapy
• Müllerian Duct Cyst
○ Failure of regression of müllerian duct remnants
○ Typically diagnosed in patients between 20-40 years;
reported prevalence of 5%
○ Midline but may be slightly paramidline; classically
teardrop-shaped cyst; no communication with urethra
○ Usually large, can extend above prostatic base ± calculi;
malignancy reported
○ Differentiation from utricle cyst is difficult; not
associated with GU anomalies
• Utricle Cyst
○ Dilation of müllerian duct remnant
○ Typically diagnosed in patients < 20 years; reported
prevalence 1-5%
○ Midline arising from verumontanum