This transcript provides a detailed pathology case review focusing on a dermal/subcutaneous nodule characterized by a prominent cellular component, scattered vessels, and eosinophilic infiltration. The speaker identifies the lesion as Angiolymphoid Hyperplasia with Eosinophilia (ALHE), also known as Epithelioid Hemangioma. Key microscopic features discussed include the deceptive appearance of a "solid nodule" due to extremely plump, epithelial-like endothelial cells compressing the vascular lumens. The presentation covers the diagnostic difficulty in distinguishing eosinophils from red blood cells, the conflicting views on whether ALHE is a reactive process or a true neoplasm, the tendency for local recurrence in patients, and the relevance of newer diagnostic markers like Fos/FosB positivity.
Angiolymphoid Hyperplasia with Eosinophilia (ALHE) / Epithelioid Hemangioma Case Review
0:16 Initial Observation: The specimen shows a cellular module, initially appearing as a solid nodule, with scattered vessels and a suggestion of "hobnailing" (a type of endothelial cell protrusion).
0:52 Cellular Identification: The nodule contains red blood cells (RBCs) and scattered eosinophils (EOS). The speaker notes that differentiating eosinophils (which are granulated) from RBCs (homogeneous texture) can be difficult at low power due to similar color.
1:31 Deceptive Morphology: The appearance of a solid nodule is a "trick." The lesion is highly vascularized, but the endothelial cells lining the channels are so plump (almost epithelial-looking) that they compress the lumens, obscuring the vascular nature.
1:52 Diagnosis: The lesion is diagnosed as Angiolymphoid Hyperplasia with Eosinophilia (ALHE) or Epithelioid Hemangioma.
2:05 Nomenclature Debate: The speaker addresses the WHO recommendation to limit the use of ALHE, noting that some cases labeled ALHE might be reactive (like exuberant vessel proliferation after a bug bite), while others (particularly deeper lesions) are true neoplasms, leading to the preference for the term Epithelioid Hemangioma.
2:42 Histological Confirmation: Immunostains (e.g., CD31, actin) would confirm the vascular nature by revealing well-formed channels surrounded by pericytes and myofibroblasts, even in areas that look solid.
3:17 Diagnostic Triad: The presence of the vascular component, lymphocytes (which may form germinal centers), and eosinophils (though varying widely in number) is essential for diagnosis.
3:45 Clinical Presentation: Classic sites include the temple or areas near a damaged vessel (like the temporal artery), sometimes arising after trauma. The growth can involve the wall and even the lumen of the artery.
4:06 Key Takeaway (Recurrence): Although benign, the lesions are problematic due to a high tendency for local recurrence, often requiring multiple surgeries.
4:40 Treatment Challenges: The lack of a single effective therapy (indicated by the variety of treatments attempted, such as lasers and anti-hypertensive agents) highlights the difficulty in managing recurrence.
4:56 Molecular Markers: About 50% of these cases are positive for Fos or FosB (detectable via immunohistochemistry or molecular testing), providing a newer tool for identification.