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Epithelioid Hemangioendothelioma (EHE) of the Lung: A Case Study

• 0:00:03 Introduction: Dr. Jared Gardner presents a case of epithelioid hemangioendothelioma (EHE) involving the lung.
• 0:00:13 EHE Behavior: EHE's behavior varies by location. In the liver or lungs, it acts more like a malignancy (though often slow-growing). In soft tissue or skin, the prognosis is generally better, depending on specifics.
• 0:00:40 Morphology: EHE is a vascular tumor, but at first glance often looks more like a carcinoma, an epithelial tumor, because of the abundant cytoplasm and arrangement in nests.
• 0:01:03 Lung Involvement: In the lung, EHE grows within the alveolar spaces, giving it a unique appearance compared to other sites.
• 0:01:48 Stroma: EHE often has a dense background stroma, which can be blue and mixoid, dense pink and hyalinized, sclerotic collagen, or a mix. This can make it look chondroid (cartilage-like).
• 0:02:31 Diagnostic Clues: Despite being vascular, EHE often lacks well-formed blood vessels. A key microscopic clue is the presence of "blister cells" - cells with cytoplasmic vacuoles containing degenerated red blood cell fragments.
• 0:03:59 Key Features: Epithelioid tumor cells, a chondromyxoid background, and blister cells with red cell fragments point towards EHE.
• 0:04:12 Immunohistochemistry: EHE stains positive with vascular markers like ERG, CD31, and CD34.
• 0:04:24 Molecular Testing: If morphology is unclear, molecular testing can confirm the diagnosis. Most EHEs have a WWTR1-CAMTA1 gene fusion, while a subset has a YAP1-TFE3 fusion.
• 0:04:50 Nuclei: EHE nuclei are large and somewhat atypical, but usually not dramatically pleomorphic (although higher-grade cases exist).
• 0:05:11 Historical Context: The intra-alveolar growth pattern initially led pathologists to mistake EHE for a type of bronchoalveolar carcinoma, previously named "intravascular bronchoalveolar tumor" (IVBAT).
• 0:05:35 Naming: Sharon Weiss and Franz Enzinger coined the term "epithelioid hemangioendothelioma," which is now the accepted name.
• 0:05:46 Rarity: EHE is a relatively rare and unique tumor.
• 0:05:51 Lung-Specific Growth: This case highlights the distinctive growth pattern of Error: Couldn't find 1429 EHE in the lung.
• 0:06:00 Further Learning: Links to additional videos and resources on EHE will be provided.