This video presents a detailed pathology case study of a schwannoma (nerve sheath tumor) identified in a 20-year-old female presenting with a 2 cm neck mass. The discussion focuses on the classic microscopic features necessary for diagnosis using Hematoxylin and Eosin (H&E) staining. Key characteristics covered include the hypercellular Antoni A areas featuring prominent nuclear palisading (Verocay bodies), and the hypocellular Antoni B areas exhibiting loose, foamy, and myxoid changes. Crucial secondary diagnostic clues are emphasized, such as hyaline sclerosis surrounding vessels and the presence of a thick, fibrous capsule that results from the tumor pushing the nerve's perineurium outward. While diagnosis is often morphological, the role of immunohistochemical confirmation (S100 and SOX10 positivity) is also noted.
Pathology Case Study: Diagnosing Schwannoma
0:00 Case Introduction: The subject is a 20-year-old female patient with a 2 cm neck mass. The diagnosis is a schwannoma.
0:24 Antoni A Areas and Palisading: Schwannomas feature hypercellular Antoni A areas. These areas exhibit pronounced nuclear palisading, where nuclei are lined up in clusters, forming characteristic Verocay bodies.
0:46 Recognizing Cellularity: Although schwannomas are benign, Antoni A areas can sometimes be highly cellular, requiring caution to distinguish them from malignancy. Mitoses are typically rare.
1:21 Subtlety of Diagnosis: Palisading can be very subtle in some schwannomas, making it essential to look for other clues. Subtle clustering of cells is also seen in other tumors like spindle cell lipoma.
2:22 Hyaline Sclerosis: A highly useful diagnostic feature is the presence of hyaline sclerosis around vessels. This prominent, reactive sclerotic change stiffens the vessel walls, even in small vessels.
3:07 Antoni B Areas: The hypocellular regions are known as Antoni B areas. These areas are loose, edematous, or myxoid, often containing foamy or frothy cells. They can sometimes mimic neurofibroma (e.g., showing "shredded carrot" type collagen).
3:46 Thick Fibrous Capsule: Schwannomas typically possess a thick, fibrous capsule on the outside. This is formed because the tumor arises within the nerve and pushes the nerve’s outer layer (perineurium) outward.
4:22 Immunohistochemistry (IHC): Schwannomas are strongly and diffusely positive for S100 protein and SOX10. However, the diagnosis is usually made based on H&E morphology alone, reserving IHC for small biopsies or unusual cases.
4:50 Diagnostic Pitfalls: Schwannomas can sometimes have significant hemorrhage, and the resulting blood-filled areas and hemosiderin deposits can lead to confusion with vascular tumors.