Angiomyolipoma pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2], Faizan Sheraz, M.D. [3]

Overview

Pathophysiology

Gross

Well circumscribed - uniform yellow.

Since all three components of an angiomyolipoma (vascular cells, immature smooth muscle cells and fat cells) contain a "second hit" mutation, they are believed to have derived from a common progenitor cell that suffered the common second hit mutation. Angiomyolipomas are members of the perivascular epithelioid cells tumour group (PEComas) and are composed of variable amounts of three components;blood vessels (-angio), plump spindle cells (-myo) and adipose tissue (-lipo). Almost all classic angiomyolipomas are benign but they do have the risk of rupture with bleeding or secondary damage/destruction of surrounding structures as they grow.

Variants

There is a special variant called an epithelioid angiomyolipoma, composed of more plump, epithelial looking cells, often with nuclear atypia, that have a described risk of malignant behaviour. This variant, unlike conventional AMLs, may mimic renal cell carcinoma.10 Metastases have also been described 9.

Microscopic Pathology

Microscopic

Features:

Smooth muscle.
Adipose tissue - not always present^[1] - key feature.
Abundant blood vessels.

1. Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. H & E stain.

2. Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. The same case as demonstrated in "Image 1". H & E stain.

3. Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. The same case as demonstrated in "Image 1". H & E stain.

4. Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. The same case as demonstrated in "Image 1". HMB-45 immunostain.

Cytologic

Features^[1]

Nuclei - round/ovoid.
Chromatin - bland.==IHC==
Melanocytic markers +ve.^[2]
- HMB-45 +ve in all cases (15/15).^[3]
- Melan A +ve in ~87% of cases (13/15).
Epithelial markers -ve^[2], e.g. EMA and AE1/AE3.
SMA +ve.
CD117 +ve/-ve.

Ki-67:^[4]
- Epithelioid variant of AML +ve.
- Conventional AML -ve.

References

↑ ^1.0 ^1.1 Crapanzano, JP. (2005). "Fine-needle aspiration of renal angiomyolipoma: cytological findings and diagnostic pitfalls in a series of five cases". Diagn Cytopathol. 32 (1): 53–7. doi:10.1002/dc.20179. PMID 15584043. Unknown parameter |month= ignored (help)
↑ ^2.0 ^2.1 Template:Ref GUP
↑ Esheba, Gel S.; Esheba, Nel S. (2013). "Angiomyolipoma of the kidney: clinicopathological and immunohistochemical study". J Egypt Natl Canc Inst. 25 (3): 125–34. doi:10.1016/j.jnci.2013.05.002. PMID 23932749. Unknown parameter |month= ignored (help)
↑ Ooi, SM.; Vivian, JB.; Cohen, RJ. (2009). "The use of the Ki-67 marker in the pathological diagnosis of the epithelioid variant of renal angiomyolipoma". Int Urol Nephrol. 41 (3): 559–65. doi:10.1007/s11255-008-9473-1. PMID 18839327.

Template:WikiDoc Sources

[pmid15584043-1] 1.0 ^1.1 Crapanzano, JP. (2005). "Fine-needle aspiration of renal angiomyolipoma: cytological findings and diagnostic pitfalls in a series of five cases". Diagn Cytopathol. 32 (1): 53–7. doi:10.1002/dc.20179. PMID 15584043. Unknown parameter |month= ignored (help)

[Ref_GUP324-2] 2.0 ^2.1 Template:Ref GUP

[pmid23932749-3] Esheba, Gel S.; Esheba, Nel S. (2013). "Angiomyolipoma of the kidney: clinicopathological and immunohistochemical study". J Egypt Natl Canc Inst. 25 (3): 125–34. doi:10.1016/j.jnci.2013.05.002. PMID 23932749. Unknown parameter |month= ignored (help)

[pmid18839327-4] Ooi, SM.; Vivian, JB.; Cohen, RJ. (2009). "The use of the Ki-67 marker in the pathological diagnosis of the epithelioid variant of renal angiomyolipoma". Int Urol Nephrol. 41 (3): 559–65. doi:10.1007/s11255-008-9473-1. PMID 18839327.

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