Also known as: immature nerve sheath myxoma

Clinical Features:

• Benign tumor of controversial histogenesis
• Most often seen in young adults, with a female predominance
• May affect any area of the body, but most common on the head and neck
• Firm pink to red-brown papule or nodule
• May recur if incompletely excised

Histologic Features:

• Ill-defined lesion filling the dermis and sometimes extending into the subcutis
• Fascicular, nodular, nested or plexiform pattern
• Composed of epithelioid to spindled cells with abundant eosinophilic cytoplasm and ovoid nuclei with prominent nucleoli
• Numerous mitoses can sometimes be seen.
• Foci of significant atypia are sometimes present.
• In contrast to classic neurothekeoma, myxoid change is not a prominent feature.
• Stromal changes can include chronic inflammation, fibrosis and hyalinization.
• The epidermis can on occasion show melanocytic hyperplasia.
• Immunohistochemistry of is of limited utility.  The tumor is negative or only weakly positive for S-100, Leu-7 (CD57), type IV collagen and EMA.  Some cases are positive for NSE, MSA or CD34.  The only universally positive immunohistochemical stain is vimentin.

Cases associated with this book:

Cellular neurothekeoma
Author: Stephen Lyle, M.D., Ph.D.

Conference: DermatopathologyConsultations.com Teaching Collection