Table of Contents
Definition / general | Terminology | Clinical features | Case reports | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Differential diagnosisCite this page: Shankar V. Benign triton tumor / neuromuscular choristoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueneuromuscularhamartoma.html. Accessed November 29th, 2023.
Definition / general
- Rare developmental lesion of mature skeletal muscle and nerve
Terminology
- Also called neuromuscular hamartoma
- Malignant triton tumor refers to rhabdomyosarcoma plus MPNST)
Clinical features
- Usually < 2 years old, affects brachial plexus or sciatic nerve
- May involve large cranial nerve trunks and present as intracranial mass
- Very rarely involves peripheral nerve and presents as small nodules
- Aggressive behavior
Case reports
- 15 year old boy with tumor of trigeminal nerve (AJNR Am J Neuroradiol 2005;26:967)
- 36 year old woman with tumor of trigeminal nerve (Acta Neurochir (Wien) 2006;148:83)
- 51 year old man with migraine (Cephalalgia 2012;32:171)
- 61 year old man with bilateral exophthalmos and lid retraction (Orbit 2010;29:168)
Treatment
- Biopsy for diagnosis plus observation, may develop fibromatosis after biopsy or complete excision
- May recur, mandating regular followup after excision
Gross description
- Circumscribed, firm, gray-brown-white, multinodular, attached to nerve
Microscopic (histologic) description
- Multiple nodules, each 3 - 5 mm, separated by narrow bands of connective tissue
- Nodules are composed of fascicles of striated muscle of varying size with nerve fibers (myelinated or not) within same perimysial fibrous sheath
- Stroma may be more cellular with bland spindle cells and resemble fibromatosis
Microscopic (histologic) images
Positive stains
- Striated muscle: desmin and muscle specific actin
- Nerve: S100, neuron specific enolase, neurofilament protein
Differential diagnosis
- Embryonal rhabdomyosarcoma:
- Poorly and moderately differentiated cells
- Fetal rhabdomyoma:
- Usually not intimately associated with nerves, S100 negative