Kidney tumor

• Member of perivascular epithelioid cell (PEC) tumor family

• Angiomyolipoma, classic variant, is a benign mesenchymal neoplasm composed of admixture of thick dysmorphic blood vessels, smooth muscle and adipose tissue
• Amount of each component is variable
• Some cases show significant sclerosis
• Epithelioid variant has potential to metastasize
• Angiomyolipoma can occur in extrarenal sites

• PEComa: perivascular epithelioid cell (PEC) tumor family

• ICD-O: 8860/0 - angiomyolipoma

• Reported in 0.13 - 2.2% of asymptomatic adults who underwent imaging studies (Eur Urol 1995;27:124, Am J Kidney Dis 2012;59:611)
• Occurs sporadically or in patients with tuberous sclerosis
• Majority are sporadic cases (80%) and usually diagnosed in middle aged adults (F > M) (Yonsei Med J 2010;51:728)
• Tuberous sclerosis cases occur in young patients and have no sex predilection (J Urol 2017;197:500)
• Constitutes ~1% of all resected renal tumors

• Presumably arises from perivascular epithelioid cells, which have no known body counterpart

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• Benign course in angiomyolipoma, classic variant
• Tumors with epithelioid and pleomorphic features can have a more aggressive course (Mod Pathol 2013;26:1355, Ann Diagn Pathol 2020;47:151538, Urol Oncol 2022;40:18)
• Sarcomatous transformation with distant metastasis is extremely rare
• Retroperitoneal hemorrhage is an important complication (Urology 2008;72:1077)
• Patients with bilateral disease can have renal failure
• Death can occur due to involvement of contiguous organs particularly blood vessels

• Tumors may be embolized or undergo surgical excision (Eur Urol 2009;55:1155)
• mTOR inhibitors such as everolimus can be used if large or extending into the vena cava (Urol Case Rep 2017;11:11)

Contributed by Tatjana Antic, M.D.

Contributed by Tatjana Antic, M.D. and Ankur R. Sangoi, M.D. (Case #359)

• Oval to spindled cells and cohesive stromal fragments, adipose tissue and branching blood vessels in a hemorrhagic background (Diagn Cytopathol 2019;47:1190)
• No mitotic figures (Cytopathology 2007;18:250)

• 5q (Hum Pathol 1999;30:295)
• TSC2 mutation in sporadic angiomyolipomas (PLoS One 2011;6:e24919)
• P53 mutation in epithelioid angiomyolipomas (Urol Oncol 2022;40:18)
• Rare cases of MDM2 amplification by fluorescence in situ hybridization in fat predominant angiomyolipomas (Virchows Arch 2020;477:661)

• Right kidney, mass, partial nephrectomy:
  • Angiomyolipoma, classic variant, measuring 3.5 cm in greatest dimension (see comment)
  • Surgical margins, negative for tumor
  • Comment: The sections show well circumscribed tumor composed of adipose tissue, thick walled blood vessels and smooth muscle. There are vessel walls with prominent sclerosis. Immunohistochemical stain SMA is diffusely positive in the vessel walls and the smooth muscle component. HMB45 is focally staining adipose tissue and smooth muscle.

• Renal cell carcinoma, clear cell type:
  • Tumors with sarcomatoid differentiation or fat invasion can be mimickers
  • Positive for AE1 / AE3, PAX8 and CAIX
  • Negative for SMA and usually negative for melanocytic markers
• Well differentiated liposarcoma:
  • No vascular component
  • Negative for melanocytic markers and SMA
• Leiomyoma:
  • No vascular or adipose component
  • Negative for melanocytic markers
• Leiomyosarcoma:
  • Prominent atypia, infiltrative, usually no vascular or adipose component
  • Negative for melanocytic markers
• Pleomorphic rhabdomyosarcoma:
  • Smooth muscle component is markedly atypical, tumor is infiltrative, no vascular or adipose component
  • Negative for melanocytic markers
• Melanoma:
  • Marked atypia, no adipose or vascular component
  • Negative for SMA
• Adrenal cortical carcinoma:
  • Usually abundant mitotic figures and marked pleomorphism
  • Both positive for MelanA but also expresses inhibin and calretinin
  • Negative for S100, HMB45, SMA, ER and PR
• Oncocytoma:
  • Cytologically bland oncocytes
  • No adipose or vascular component
  • Negative for melanocytic markers and SMA

A 16 year old girl with history of seizures was found to have bilateral renal masses containing a fat component on the CT imaging study. Histology is shown in the image above. Which hereditary disease is this patient likely to have?


1. Birt-Hogg-Dubé
2. Familiar papillary renal cell carcinoma
3. Hereditary leiomyomatosis
4. Tuberous sclerosis
5. von Hippel-Lindau

D. Tuberous sclerosis. This H&E image of an angiomyolipoma, together with the clinical history of seizures in a young female, is consistent with tuberous sclerosis.

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Reference: Angiomyolipoma

A renal tumor from a 43 year old woman shows proliferation of epithelioid cells with abundant eosinophilic cytoplasm and prominent nuclear atypia. What is the best initial immunohistochemical panel for this case?


1. Cytokeratin, PAX8, CAIX, CD10, vimentin
2. Cytokeratin, PAX8, CK7, CK20, p53
3. Cytokeratin, PAX8, MDM2, MyoD1, desmin
4. Cytokeratin, PAX8, MITF, S100, tyrosinase
5. Cytokeratin, PAX8, SMA, HMB45, inhibin

E. Cytokeratin, PAX8, SMA, HMB45, inhibin. Differential diagnosis includes high grade renal cell carcinoma, epithelioid angiomyolipoma and metastatic tumors such as melanoma and adrenal cortical carcinoma. Although the panel including cytokeratin and PAX8 could provide a diagnosis of renal cell carcinoma and any panel including HMB45 should be helpful in diagnosing melanoma, the only panel that can help with a diagnosis of epithelioid angiomyolipoma is one that includes SMA.

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Reference: Angiomyolipoma