Soft tissue
Peripheral nerve
Other benign
Benign triton tumor / neuromuscular choristoma
Author: Vijay Shankar, M.D.
Last author update: 1 November 2012
Last staff update: 26 April 2023
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: Neuromuscular hamartoma
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 June 6th, 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
AFIP images
Nodules of
skeletal muscle
and neural
elements
Nodules contain
fascicles and nerve
fibers in perimysial
fibrous sheath
Rare case with haphazardly distributed skeletal muscle and nerve fibers, cellular stroma and bland spindle cells with scant cytoplasm and oval nuclei
Nerve fibers are S100+
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
