Encyclopedia of Pathology

Living Edition
| Editors: J.H.J.M. van Krieken

Angiomyolipoma, Mediastinal

  • Ronda Sanders
  • Merce JordaEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-28845-1_3283-1

Angiomyolipoma is a usually benign mesenchymal neoplasm composed of smooth muscle, blood vessels, and adipose tissue in varying amounts (Morita et al. 2012). It occurs predominantly in the kidney but can rarely occur in extrarenal locations including the liver, lungs, and the mediastinum (Candaș et al. 2013). Though they may be sporadic in origin, angiomyolipomas are associated with tuberous sclerosis and TSC2/PKD1 contiguous gene syndrome (Martignoni et al. 2002). Patients with a genetic syndrome tend to present at a younger age than patients without a genetic mutation. Angiomyolipomas belong to the perivascular epithelioid cell tumor (PEComa) family, which means they have perivascular and epithelioid features and can coexpress melanocytic and muscle markers. The PEComa family includes angiomyolipoma (AML), clear-cell sugar tumor (CCST) of the lung, lymphangioleiomyomatosis (LAM), clear-cell myomelanocytic tumor of the falciform ligament/ligamentum teres, and other rare clear-cell tumors (Martignoni et al. 2008).

Clinically, angiomyolipomas usually behave benignly. However, the epithelioid variant has risk of malignant behavior and thus carries a worse prognosis (Park et al. 2016). They also carry a risk of hemorrhage, risk of invasion of adjacent organs, and risk of metastasis. Patients with mediastinal angiomyolipomas may present with chest pain and/or shortness of breath (Liang et al. 2015). A characteristic feature on imaging is the presence of macroscopic adipose tissue. CT-guided percutaneous transthoracic needle biopsy may be performed prior to definitive treatment. The definitive treatment of angiomyolipomas is surgical excision.

On gross examination, angiomyolipomas are nonencapsulated, well- circumscribed, and may have a pushing border. Capsular invasion is present in approximately 25% of cases. On sectioning, angiomyolipomas may have a predominantly red, yellow, or white cut surface depending on proportion of vascular tissue, adipose tissue, and smooth muscle in the tumor. Sporadic cases are usually unifocal and unilateral. A genetic syndrome should be considered if a patient presents with multifocal or bilateral disease. Though they may invade local lymph nodes, this is not considered a sign of malignancy (Llarena Ibarguren et al. 1991).

On microscopic examination, angiomyolipomas have thick-walled hyalinized blood vessels (Fig. 1), mature adipose tissue (Fig. 2), and smooth muscle (Fig. 3). The epithelioid variant will have clear or eosinophilic polygonal cells that contain abundant cytoplasm (Fig. 4). These cells also have well-defined cell borders. The cells may be pleomorphic and sometimes may even have multilobulated nuclei. Necrosis is often present in the epithelioid variant as well.
Fig. 1

Thick blood vessels in angiomyolipoma

Fig. 2

Mature adipose tissue in angiomyolipoma

Fig. 3

Smooth muscle in angiomyolipoma

Fig. 4

Angiomyolipoma, epithelioid variant with eosinophilic cells

As mentioned before, angiomyolipoma is part of the PEComa family and therefore stains positive for melanocytic markers such as HMB45 (Fig. 5) and Melan-A/MART-1. It also stains positive with muscle markers (smooth muscle actin, muscle-specific actin, calponin, and desmin). Other positive stains include S100, CD117, and vimentin. Angiomyolipomas are negative for cytokeratins.
Fig. 5

Positive HMB-45 immunostain in angiomyolipoma

Differential diagnosis includes thymoma especially if the thymoma has a spindled cell morphology and solitary fibrous tumor among other entities. These however will not be positive for melanocytic markers.

References and Further Reading

  1. Candaș, F., Berber, U., Yildizhan, A., Yiyit, N., Görür, R., & Ișitmangil, T. (2013). Anterior mediastinal angiomyolipoma. The Annals of Thoracic Surgery, 95(4), 1431–1432.CrossRefPubMedGoogle Scholar
  2. Liang, W., Xu, S., & Chen, F. (2015). Malignant perivascular epithelioid cell neoplasm of the lung: One case report. Medicine (Baltimore), 94(22), 904.CrossRefGoogle Scholar
  3. Llarena Ibarguren, R., et al. (1991). Renal angiomyolipoma with lymphatic involvement. Archivos Españoles de Urología, 44(1), 75–76.PubMedGoogle Scholar
  4. Martignoni, G., et al. (2002). Renal disease in adults with TSC2/PDK1 contiguous gene syndrome. The American Journal of Surgical Pathology, 26(2), 198–205.CrossRefPubMedGoogle Scholar
  5. Martignoni, G., Pea, M., Reghellin, D., et al. (2008). PEComas: The past, the present and the future. Virchows Archiv, 452(2), 119–132.CrossRefPubMedGoogle Scholar
  6. Morita, K., et al. (2012). Angiomyolipomas of the mediastinum and lung. Journal of Thoracic Imaging, 27(1), W21–W23.CrossRefPubMedGoogle Scholar
  7. Park, J. H., Lee, C., Suh, J. H., Kim, G., Song, B., & Moon, K. C. (2016). Renal epitheliod angiomyolipoma: Histopathologic review, immunohistochemical evaluation and prognostic significance. Pathology International, 66(10), 571–577.CrossRefPubMedGoogle Scholar

Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.Department of Pathology and Laboratory Medicine and Department of UrologyUniversity of Miami Miller School of MedicineMiamiUSA