Granulomatous prostatitis

Granulomatous prostatitis, also known as prostatic granuloma and prostate gland granuloma, is an uncommon benign finding of the prostate.

Granulomatous prostatitis
Diagnosis in short
Granulomatous prostatitis. H&E stain.
LM	granulomas +/- eosinophils
Subtypes	non-specific, post-TURP, specific, allergic
LM DDx	disseminated granulomatous diseases
Stains	GMS stain, Ziehl-Neelsen stain
Site	prostate gland
Prevalence	uncommon
Radiology	may be PI-RADS 4 or 5
Prognosis	dependent on underlying etiology
Clin. DDx	other types of prostatitis, prostate carcinoma

Granulomatous prostatitis
External resources
EHVSC	10148

General

• Common.
• Usually secondary to BCG treatment of bladder cancer.
• Several classifications exist - the most commonly used is by Epstein & Hutchins.

Epstein & Hutchins classification

The groupings:

1. Non-specific.
   • No cause identified, usu. incidentally discovered.
   • Most common.
2. Post-TURP. ‡
   • Palisading granuloma with necrotic core (histology similar to a rheumatoid nodule) +/- eosinophils.
3. Specific.
   • Identifiable infectious agent, usu. BCG (in the context of treating bladder cancer), rarely tuberculosis and even more rarely various fungi and syphilis.
4. Allergic granulomatous prostatitis.
   • Usually associated with eosinophils.
   • Examples:
     1. Granulomatosis with polyangiitis (Wegener granulomatosis).
     2. Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome).

Note:

• ‡ May also be seen post-biopsy.

Gross/Imaging

• MRI findings may mimic significant prostate cancer (PI-RADS 4 or 5).

Microscopic

Features:

• Granulomas in the prostate - key feature.
  • +/-Palisading granulomas with a necrotic core (similar to a rheumatoid nodule) - consistent a with prior TURP.
• +/-Eosinophils.

Images

• 

  Granulomatous inflammation of the prostate/bladder neck - low mag. (WC/Nephron)

• 

  Granulomatous inflammation of the prostate/bladder neck - high mag. (WC/Nephron)

Stains

• GMS stain.
• Ziehl-Neelsen stain.

Note:

• Stains are indicated when there is a suspicion of an infective etiology based on histomorphology (necrosis) or clinical information (e.g. immunosuppression).

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Post-TURP

Prostate Tissue, Transurethral Resection of the Prostate (TURP):
	- Benign prostatic tissue with glandular and stromal proliferation.
	- Palisading granulomas with necrotic cores and scarring, see comment.

COMMENT:
The granuloma morphology is consistent with post-TURP changes.

Block letters

PROSTATE GLAND, TRANSURETHRAL RESECTION OF THE PROSTATE (TURP):
- BENIGN PROSTATIC TISSUE WITH GLANDULAR AND STROMAL PROLIFERATION.
- PALISADING GRANULOMA WITH NECROTIC CORE, SEE COMMENT.

COMMENT:
This is morphologically consistent with a post-TURP granuloma.

Idiopathic

A-L. PROSTATE GLAND,
 RIGHT LATERAL SUPERIOR, RIGHT MEDIAL SUPERIOR, RIGHT LATERAL MIDZONE,
 RIGHT MEDIAL MIDZONE, RIGHT LATERAL INTERIOR, RIGHT MEDIAL INFERIOR,
 LEFT LATERAL SUPERIOR, LEFT MEDIAL SUPERIOR, LEFT LATERAL MIDZONE, 
 LEFT MEDIAL MIDZONE, LEFT LATERAL INTERIOR, LEFT MEDIAL INFERIOR, 
  CORE BIOPSIES:
	- BENIGN PROSTATE TISSUE;
	- GRANULOMATOUS PROSTATITIS, NON-NECROTIZING, SEE COMMENT.

COMMENT:
Granulomatous prostatitis is usually idiopathic. Other possibilities include: 
post-procedural granulomatous inflammation (e.g. post-TURP, BCG treatment), 
allergic prostatitis and infections.

Infectious etiologies of granulomatous disease should be considered clinically.

Isolated granuloma without necrosis

D. PROSTATE, RIGHT MEDIAL INFERIOR, BIOPSY:
- BENIGN PROSTATE TISSUE;
- ACUTE AND CHRONIC INFLAMMATION;
- FOCAL GIANT CELLS AND AN ISOLATED GRANULOMA WITHOUT APPARENT NECROSIS.

COMMENT:
The granuloma (Part D) is histologically favoured to be nonspecific (as
most prostate granulomas are); however, this finding should be interpreted
within the clinical context.

Periprostatic foreign body-type

D. PROSTATE, RIGHT MEDIAL MIDZONE, BIOPSY:
- BENIGN PROSTATE TISSUE;
- FOREIGN BODY-TYPE GRANULOMA, NON-NECROTIZING, SEE COMMENT.

COMMENT:
The granuloma appears to be within the periprostatic soft tissue. It consists 
of multinucleated (foreign body-type) giant cells, hyaline material, and rare 
interspersed neutrophils. No necrosis is identified. This finding may represent 
a reaction to displaced epithelium.

See also

• Prostate gland.
• Genitourinary pathology