Seminal vesicle amyloidosis refers to the deposition of amyloid in the seminal vesicles and can occur as organ-limited amyloidosis and/or as part of systemic amyloidosis.
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Epidemiology
Amyloid deposition in the seminal vesicles is apparently commonly seen in elderly men with a prevalence ranging from 16%-21% is more commonly seen in the localized form 1-3. It has been also reported in up to 10% of radical prostatectomy specimens.
Diagnosis
The diagnosis of seminal vesicle amyloidosis is made histologically by proof of amyloid deposits in the subepithelium or the lamina propria of both seminal vesicles 1,2.
Clinical presentation
Clinically seminal vesicle amyloidosis can present with hematospermia.
Pathology
Amyloid deposits of the seminal vesicles occur characteristically in the subepithelium or the lamina propria. In the localized form, both seminal vesicles are involved. On the other side amyloid deposits in vessel walls or within the muscular tissue indicates systemic amyloidosis 1,2.
Etiology
In the seminal vesicles, amyloid is apparently derived from semenogelin 1, which is a secretory product of the seminal vesicles and is thought to have a role in the localized form 4.
Microscopic appearance
Amyloidosis is characterized by the deposition of amyloid fibrils in the extracellular space which appears as an apple-green birefringence under polarized light and can be positively stained with Congo red 1. Beyond that amyloid looks like an amorphous pale eosinophilic substance that often features cracks.
Immunophenotype
Immunohistochemistry stains are usually positive for AP protein in localized amyloidosis. Tryptophan was
Radiographic features
MRI
Imaging features of seminal vesicle amyloidosis on magnetic resonance imaging show some similarities with seminal vesicle invasion and include:
- wall thickening
- luminal narrowing
Other than seminal vesicle invasion seminal vesicle amyloidosis does not tend to show any diffusion restriction or early contrast enhancement 5.
Signal characteristics
- T1: hyperintense
- T2: hypointense walls
- DWI: lack of diffusion restriction
- DCE (Gd): lack of normal enhancement
Radiology report
The radiological report should include a description of the following:
- luminal narrowing
- associated findings of the prostate
History and etymology
There are diverse descriptions of amyloid in the seminal vesicles in the 1920s e.g. by M Winkelmann in 1927 6.
Differential diagnosis
Conditions that may mimic the clinical presentation or imaging appearance of 2-4:
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