Congenital Smooth Muscle Hamartoma
Steven D. Billings, MD
Key Facts
Terminology
Rare lesion presenting in infants, characterized by disorganized proliferation of benign smooth muscle bundles in dermis, often involving subcutis
Clinical Issues
Infants
Most common in lumbosacral area
Macule or plaque
Often hyperpigmented, may have coarse hairs
Microscopic Pathology
Benign smooth muscle bundles
Haphazard arrangement
Thin fascicles rather than solid growth pattern
No atypia
No mitoses
No necrosis
 Hematoxylin & eosin shows a haphazard arrangement of smooth muscle bundles in the dermis. |
 Hematoxylin & eosin shows a fascicular arrangement of smooth muscle with characteristic elongated blunt-ended nuclei. |
TERMINOLOGY
Synonyms
Smooth muscle hamartoma
Definitions
Rare benign smooth muscle tumor presenting in infants
Characterized by disorganized proliferation of smooth muscle bundles
CLINICAL ISSUES
Epidemiology
Age
Infants
Site
Lumbosacral area and proximal extremities
Presentation
Macule or plaque
Indurated
Often hyperpigmented
May have coarse hairs
Pseudo-Darier sign
Piloerection induced by mechanical stimulation
Occasionally presents as multiple lesions
Occasional familial cases
Treatment
Surgical approaches
Simple excision
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