Amyloidoma
Cyril Fisher, MD, DSc, FRCPath
Key Facts
Terminology
Solitary localized tumor-like deposit of amyloid in absence of systemic amyloidosis
Macroscopic Features
Pale waxy cut surface
Microscopic Pathology
Amorphous acellular eosinophilic material
Adjacent lymphoplasmacytic infiltrate
Ancillary Tests
Congo red
Apple-green areas in polarized light
AL amyloid is permanganate resistant
Top Differential Diagnoses
Elastofibroma
Amianthoid fibers
Fibrin deposits
Tumoral calcinosis
 Hematoxylin & eosin shows irregular-shaped amyloid deposits  with adjacent stroma containing inflammatory cells. |
 Congo red stain shows the intense red (congophilic) coloration of amyloid. Note the slight variation in staining intensity and the angulated shape and distinct demarcation of the deposits. |
TERMINOLOGY
Synonyms
Tumoral amyloidosis
Definitions
Solitary localized tumor-like deposit of amyloid in absence of systemic amyloidosis
ETIOLOGY/PATHOGENESIS
Idiopathic
No associated disease
Immune Dyscrasias
Myeloma, plasmacytoid lymphoma
AL (light chain) amyloid
Green birefringence resistant to pre-treatment with potassium permanganate
Long-term Hemodialysis
β2 microglobulin deposition
Chronic Inflammation
Rheumatoid arthritis
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