Microscopic Description:

Tumor is composed of blood vessels, smooth muscle, and adipose tissue.

H&E-stained sections reveal mature adipocytes surrounded by spindle-shaped smooth muscle cells and thick-walled, congested blood vessels. The three components of the tumor are adipose tissue, smooth muscle cells, and irregular blood vessels.

 These cells lack signs of malignancy, and should show no evidence of atypia, mitotic activity.

Immunohistochemistry  show positive staining for expression of MelanA and HMB45, and negative for PAX8.

Smooth muscle antigen (SMA) is positive for smooth muscle bundles which are a predominant component of the tumor.

Discussion:

Angiomyolipoma is the most common benign tumor. They most often originate in the kidneys and are a type of perivascular epithelioid cell tumors.

They are typically asymptomatic and benign, noncancerous. They are typically discovered incidentally.

  • Though normally asymptomatic and slow-growing, when they start to compress/impact nearby structures and organs, they can cause symptoms such as abdominal pain, hematuria, anemia, and hypertension.

Angiomyolipoma usually occur in people from the ages of 40 to 60 years of age. It is more prevalent in women than men.

Angiomyolipoma are benign, mesenchymal tumors composed of a well-differentiated mixture of adipose tissue, smooth muscle cells, and blood vessels. Lack of cellular atypia and mitotic activity distinguishes them from neuroblastoma and renal cell carcinoma.

Histologically, angiomyolipoma is characterized by a disorganized mixture of adipose tissue, smooth muscle cells, and blood vessels.

The IHC profile of ganglioneuroma shows expression of melanocytic markers MelanA or HMB45.

The primary treatment for angiomyolipoma is the surgical removal of the tumor if it starts to rapidly grow or impact other body structure and cause symptoms.

  • Large tumors (>4 cm) pose a risk of spontaneous hemorrhage which is why surgery is necessary.
References:

Fejes Z, Sánta F, Jenei A, Király IE, Varga L, Kuthi L. Angiomyolipoma of the kidney-Clinicopathological analysis of 52 cases. Pathol Oncol Res. 2023;28:1610831. Published 2023 Jan 9. doi:10.3389/pore.2022.1610831

He, W., Cheville, J., Sadow, P. et al. Epithelioid angiomyolipoma of the kidney: pathological features and clinical outcome in a series of consecutively resected tumors. Mod Pathol 26, 1355–1364 (2013). https://doi.org/10.1038/modpathol.2013.72

Jinzaki M, Silverman SG, Akita H, Nagashima Y, Mikami S, Oya M. Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management. Abdom Imaging. 2014;39(3):588-604. doi:10.1007/s00261-014-0083-3

Nelson CP, Sanda MG. Contemporary diagnosis and management of renal angiomyolipoma. J Urol. 2002 Oct;168(4 Pt 1):1315-25. doi: 10.1016/S0022-5347(05)64440-0. PMID: 12352384.

Rout P, Leslie SW. Renal Angiomyolipoma. In: StatPearls. Treasure Island (FL): StatPearls Publishing; May 2, 2024.

Sanchez NG, Ávila Romay AA, Martínez Luna E, Padilla Rodríguez AL. Cutaneous Angiomyolipoma-A Distinct Entity That Should Be Separated From Classic Angiomyolipoma: Complete Review of Existing Cases and Defining Fundamental Features. JMIR Dermatol. 2022;5(3):e40168. Published 2022 Sep 27. doi:10.2196/40168

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