This presentation provides a detailed pathological review of Case 11: an 80-year-old male with a pink, cratered, scaly papule on the nose, initially clinically suspected to be squamous cell carcinoma (SCC). The subsequent histology reveals a challenging diagnosis: an epithelioid angiosarcoma presenting in a nodular and sheet-like proliferation in the dermis of sun-damaged skin. The speaker highlights the deceptive morphology, noting the atypical, dark blue/purple cells that can mimic poorly differentiated carcinoma (due to keratin expression) or melanoma (due to atypical nuclei). Key diagnostic features emphasized are the characteristic "slate blue/purple" color, the presence of malignant vascular channels, and "hob-nailed" endothelial cells protruding into lumens. The speaker stresses the importance of hunting for these vascular structures, especially in partial biopsies, and recommends using ERG and CD31 immunohistochemistry to confirm the diagnosis, cautioning against relying solely on CD34, which can be negative.
Pathological Review of Case 11: Epithelioid Angiosarcoma Mimicking SCC
00:00:08 Case Presentation: 80-year-old male with a pink, crateriform papule on the nose, clinically suspected to be Squamous Cell Carcinoma (SCC).
00:00:48 Histopathology Overview: Features a dense, nodular, sheet-like proliferation of dark blue/purple cells filling the dermis. Initial appearance was highly misleading clinically.
00:01:30 Atypical Morphology: Shows very ugly epithelioid cells with atypical nuclei filling the dermis in sheet-like areas, sometimes with a nested look. Weak, focal keratin expression was noted.
00:01:54 Differential Diagnosis & Immunohistochemistry (IHC): Differential included melanoma, poorly differentiated carcinoma, and the final diagnosis. Sox 10 was negative.
00:02:17 Diagnostic Pitfall in Biopsies: Caution against missing the diagnosis on shallow or partial biopsies, especially when keratin expression is strong, which can lead to misdiagnosis as carcinoma.
00:03:44 Keratin Staining: Mostly negative, but some weak focal staining was present, illustrating how it can confuse the diagnosis toward carcinoma.
00:04:10 Diagnostic Clue (Color): The characteristic bluish-purple or slate blue-gray color of the cytoplasm is a key pointer toward the actual diagnosis.
00:04:28 Key Feature: Vascular Channels: The diagnosis is Epithelioid Angiosarcoma, identified by finding malignant vascular channel formation with "hob-nailed" endothelial cells protruding into the lumen.
00:04:56 Nest Mimicry: Nesting appearance is often caused by malignant vascular lumens filling up due to multi-layering of tumor cells.
00:05:56 Recommended IHC Panel: To avoid missing epithelioid angiosarcoma when considering sarcomas or ugly epithelial tumors, the speaker recommends including ERG or CD31.
00:07:01 Vascular Marker Results: CD31 shows diffuse, strong expression. The speaker notes they have never personally seen an angiosarcoma negative for ERG or CD31.
00:07:26 Key Takeaway: Do not rely on CD34 alone to rule out vascular tumors, as it was negative or patchy in this case and other angiosarcomas.
00:08:01 Hobnailing: While hobnailing can occur in benign lesions, ugly, atypical, multi-layered hobnailing strongly suggests malignancy (angiosarcoma).
00:08:32 Growth Pattern: Angiosarcomas grow by dividing dermal collagen and wrapping around structures, demonstrating an infiltrative and anastomosing channel pattern.