This pathology case review focuses on a liver lesion in a 40-year-old female, diagnosed as Epithelioid Hemangioendothelioma (EHE). The analysis highlights the distinctive microscopic features, including a dense, homogeneous, bluish-pink "chondromyxoid" stroma often colorfully referred to as "Periwinkle blue." EHE is classified as a vascular neoplasm of intermediate malignant potential. Key diagnostic findings include the proliferation of epithelioid cells in cords and nests, often plugging existing vessels, and the presence of "blister cells"—cytoplasmic vacuoles containing fragmented red blood cells, which represent attempted but aborted lumen formation. The video emphasizes the importance of recognizing the tumor’s characteristic appearance, its potential for serious clinical outcomes, and its associated molecular features, primarily the WWTR1-CAMTA1 fusion.
Epithelioid Hemangioendothelioma (EHE) Case Review
0:08 Case Introduction: The video examines a liver lesion in a 40-year-old female, noting the abnormal tissue replacing normal hepatocytes.
1:06 Key Visual Clue: The Matrix: The dense, bluish-pink background stroma is highlighted, often described as "chondromyxoid" or, more uniquely, a "Periwinkle blue" color (1:37). This dense, homogeneous matrix facing out normal tissue is characteristic of this entity.
2:56 Diagnosis and Malignancy: The definitive diagnosis is Epithelioid Hemangioendothelioma (EHE). This is a vascular neoplasm of intermediate malignant potential (a classification used for tumors that fall between benign hemangiomas and highly aggressive angiosarcomas).
3:51 Classification Caution: The speaker stresses that different types of hemangioendotheliomas (EHE, Kaposiform, Pseudomyogenic) are separate, unique entities with distinct molecular features and behaviors, and pathologists should never use the wastebasket diagnosis of "Hemangioendothelioma NOS" (Not Otherwise Specified).
4:04 Historical Context and Clinical Features: EHE was historically mistaken for carcinoma due to its epithelioid appearance and general lack of definitive vascular channels (a finding later disproven by Dr. Sharon Weiss).
4:44 Clinical Presentation: EHE frequently presents as multiple lesions in the liver and lungs. Although often slow-growing, it can metastasize and be fatal, making it the most clinically problematic of the hemangioendothelioma types.
6:25 Diagnostic Microscopic Feature: The tumor cells often grow by filling or "plugging" existing vessels (6:13). The classic and most helpful diagnostic finding is the "blister cell" (6:56), which is an epithelioid cell containing an intracellular vacuole with fragmented red blood cells inside.
7:15 Differential Diagnosis: EHE can express keratin, making it easy to mistake for carcinoma. The presence of vacuolization alone is common in many epithelioid vascular tumors, but the internal red cell fragments (the true blister cell) are highly characteristic of EHE.
8:09 Molecular Pathology: The characteristic molecular alteration in the majority of EHE cases is the WWTR1-CAMTA1 fusion. A smaller subset carries the YAP1-TFE3 fusion; this variant may occasionally form true vascular channels, providing an exception to the general rule.