Secondary amyloidosis diagnostic study of choice

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Sahar Memar Montazerin, M.D.[2]

Overview

The diagnostic study of choice in amyloidosis is tissue biopsy of the affected organ. Urinary protein measurement followed by renal biopsy is the gold standard of the diagnosis.

Diagnostic Study of Choice

• Since AA amyloidosis is a condition that occurred due to another illness, the diagnostic study of choice varies according to the primary disorder.
• However, the amyloidosis itself should be confirmed through histologic examination of the affected organs.
• A tissue biopsy of the affected organ is the gold standard test for amyloidosis. Particular stains can determine the subtype of amyloidosis.
• Kidney is affected to a greater extent compared to other organs. The 24-hour urine collection with the assessment of urinary protein may be useful and in the case of renal involvement, a kidney biopsy is required.
• Staining the tissue sample with antibodies that are specific for AA amyloidosis will confirm the final diagnosis.
• Organ-specific labs: If a particular organ is affected, laboratory measurements that are specific to that organ can be measured. For example, if there is liver involvement, liver function tests (such as AST, ALT, total bilirubin, and alkaline phosphatase) should be measured.

Diagnostic Criteria

• Following diagnostic criteria has been used for AL amyloidosis. However, it may be applicable for AA amyloidosis as well.

Primary tumor (T)
Stage	Finding
	Spine	Pelvis	Appendicular skeleton, trunk, skull, and facial bones
Tx	Cannot be assessed	Cannot be assessed	Cannot be assessed
T0	No evidence of primary tumor	No evidence of primary tumor	No evidence of primary tumor
T1	Confined to one vertebral segment or two adjacent vertebral segments	Confined to one pelvic segment with no extraosseous extension	Tumor ≤8 cm in greatest dimension
T2	Confined to three adjacent vertebral segments	Confined to one pelvic segment with extraosseous extension or two segments without extraosseous extension	Tumor >8 cm in greatest dimension
T3	Confined to four or more adjacent vertebral segments, or any nonadjacent vertebral segments	Spanning two pelvic segments with extraosseous extension	Discontinuous tumors in the primary bone site
T4	Extension into the spinal canal or great vessels	Spanning three pelvic segments or crossing the sacroiliac joint	_
Regional lymph nodes (N)
Stage	Finding
Nx	cannot be assessed
N0	No regional lymph node metastasis
N1	Regional lymph node metastasis
Distant metastasis (M)
Stage	Finding
M0	No distant metastasis
M1	Distant metastasis
M1a	Distant metastasis to lung
M1b	Distant metastasis to bone or other distant sites
Histologic grade (G)
Stage	Finding
Gx	cannot be assessed
G1	Low grade
G2	High grade (moderately differentiated)
G3	High grade (poorly differentiated)
G4	Undifferentiated