This short educational segment addresses a persistent nomenclature problem in dermatopathology concerning the classification of certain nerve sheath tumors. The speaker advocates for the term "nerve sheath myxoma" (NSM), describing it as a multi-nodular, hypocellular myxoid proliferation of the nerve sheath, which is invariably S100 positive and likely represents a variant of schwannoma. The core confusion arises because NSM (previously called conventional/myxoid neurothekeoma) shares a similar name with "cellular neurothekeoma." The speaker emphasizes the critical distinction: cellular neurothekeoma is S100 negative, non-neural, and a fundamentally different entity, despite the confusing historical terminology.
Nomenclature Confusion in Nerve Sheath Tumors: Nerve Sheath Myxoma vs. Cellular Neurothekeoma
0:19 Diagnostic Issue: The speaker highlights a major confusing nomenclature issue in dermatopathology (second only to dysplastic nevus) where two unrelated entities were given similar names.
0:30 Preferred Terminology: The speaker prefers the term nerve sheath myxoma (NSM) for what was formerly known as conventional or myxoid neurothekeoma.
0:34 Histological Features: NSM presents as a myxoid proliferation of the nerve sheath, forming multiple hypocellular, myxoid nodules with bland spindled or stellate cells, often separated by collagen bundles. The hand is a common site for these multi-nodular tumors.
0:53 Key Takeaway (Neural Origin): Nerve sheath myxomas are true neural tumors and will always be S100 positive. They are considered variants of schwannoma.
1:05 Historical Naming: The dermal nerve sheath myxoma was previously known as "conventional or myxoid neurothekeoma."
1:14 The Source of Confusion: Later, similar-looking lesions with more cellular nodules (containing histiocyte-like cells) were named "cellular neurothekeomas."
1:22 Critical Distinction: Cellular neurothekeoma is S100 negative, non-neural, and a totally different entity, despite the misleading name, leading to "deep deep hurt" in the field due to confusing terminology.
1:45 Summary of Distinctions: Nerve sheath myxoma (S100 positive) is the former conventional neurothekeoma, while cellular neurothekeoma (S100 negative) is not neural at all.