This presentation reviews a challenging dermatopathology case involving an erythematous papule from an adult patient's nose, initially suspected clinically to be a ruptured cyst or Basal Cell Carcinoma. Histological examination immediately confirmed the presence of a ruptured cystic hair follicle with associated inflammation and keratin spillage. However, within the inflammatory background, the presenter highlights enlarged, slightly atypical, and pleomorphic cells that did not fully conform to expected histiocytes. Further investigation via immunohistochemistry, specifically a CD31 vascular stain, revealed that these atypical cells were strongly positive endothelial cells forming complex, infiltrative, and anastomosing vascular channels characterized by multilayering and hobnailing. The final diagnosis was Angiosarcoma incidentally associated with the adjacent ruptured cyst. The case serves as a critical reminder for pathologists to scrutinize the entire slide and avoid prematurely concluding a diagnosis based on the first finding observed.
Angiosarcoma Masquerading as a Ruptured Cyst
0:07 Case Introduction: The specimen is an erythematous papule from an adult patient's nose, clinically suspected to be a ruptured cyst or Basal Cell Carcinoma.
0:30 Initial Histological Finding (The Red Herring): Microscopic examination confirms the presence of an obvious ruptured cyst or cystic hair follicle, with spilled keratin and surrounding inflammation.
0:53 Recognizing Atypia: Closer inspection of the background inflammatory infiltrate reveals enlarged, pleomorphic, and slightly atypical cells. These cells resembled expected histiocytes but were unusual and suspicious.
1:19 Diagnostic Intervention: A colleague correctly recognized the unusual nature of the cells and performed a vascular stain.
1:33 Definitive Vascular Marker: Immunohistochemistry using CD31 showed strong positivity in all the atypical cells in the background.
1:43 Key Pathologic Features: The positive cells formed infiltrative, anastomosing vascular channels, displaying multi-layering and hobnailing of large, atypical endothelial cells.
1:57 Final Diagnosis: The definitive diagnosis is Angiosarcoma, which happened to be incidentally adjacent to the benign ruptured cyst.
2:09 Takeaway Message: The case highlights the necessity of thoroughly examining the entire slide and not ceasing the diagnostic search after finding an initial, plausible explanation (like a ruptured cyst). The malignancy was easily overlooked due to the prominent benign finding.