This transcript details the analysis of a mixoid finger lesion from a 34-year-old female, leading to the diagnosis of Nerve Sheath Myxoma (previously known as mixoid neurothekeoma). The lesion exhibits a highly characteristic, sharply circumscribed, multi-lobular architecture with prominent mixoid stroma. A striking, although unusual, feature observed is the presence of nuclear palisading resembling Verocay bodies, suggesting a link to schwannoma-like appearances within this entity. Immunohistochemistry confirms its true neural origin (S100 and Sox 10 positive). The presenter emphasizes the distinction between this benign tumor and cellular neurothekeoma and discusses the typical "whirling" pattern of spindle cells within the mixoid matrix.
Pathology Case Review: Nerve Sheath Myxoma
0:00 Case Introduction: Reviewing slide #9, a finger lesion from a 34-year-old female. Initial differential included myxoma due to the mixoid appearance.
0:34 Highly Characteristic Architecture: The lesion is sharply circumscribed into multiple lobules separated by fibrous septa. This multi-nodular pattern within a mixoid background is characteristic of this entity, often found on acral (hand/foot) surfaces.
1:12 Unexpected Schwannoma-like Feature: The tumor occasionally exhibits areas of nuclear palisading with intervening spaces, strikingly resembling Verocay bodies, which are typically seen in Schwannomas.
1:33 Definitive Diagnosis: The lesion is a Nerve Sheath Myxoma (historically called conventional neurothekeoma or mixoid neurothekeoma).
1:48 True Neural Origin: Immunohistochemically, Nerve Sheath Myxoma is S100 positive and Sox 10 positive, confirming it as a true neural tumor.
2:01 Historical Context: The presence of palisades supports previous research suggesting that mixoid, multi-nodular lesions previously misclassified as "mixoid variants of schwannoma" are actually Nerve Sheath Myxomas, confirming their nerve sheath origin.
2:48 Typical Morphology: The most common pattern involves spindle cells that "swirl around" or follow irregular rows in a loose mixoid background, creating a "vague whirling dance."
3:16 Key Takeaway (Prognosis and Differentiation): Nerve Sheath Myxomas are benign and unrelated to Cellular Neurothekeoma. They do not develop cellular nodules (though Cellular Neurothekeoma may have mixoid areas).
3:56 Final Note: Although benign, they can occasionally recur.