Fibrous hamartoma of infancy is a rare benign tumor of the subcutaneous tissues seen in children. More than 90% of cases present in the first year of life with up to 25% being congenital 1.
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Epidemiology
There is a reported male:female ratio of 2:1 but the exact incidence is unknown 2.
Clinical features
Presentation is usually with a painless, mobile lump that is usually less than 5 cm. It is commonly around the trunk or extremities though it can occur in the head and neck regions as well.
Pathology
Histologically these lesions are comprised of three distinct tissue/cell components 1,2:
- intersecting trabeculae of mature fibrous tissue
- islands of immature mesenchymal tissue
- mature adipose tissue
- can predominant lesions
The precise mixture of the various components in individual tumors determine their imaging characteristics.
Radiographic features
Ultrasound
- heterogenous hyperechogenecity
- serpentine intervening hypoechoic portions
- margins well defined or lobulated
- vascularity is minimal if present
MRI
Features include 4:
- fatty component is T1 and T2 hyperintense
- often predominates the lesion
- fibrous tissue is T1 and T2 hypointense
- often arranged in intersecting trabeculae
- isointense to muscle
- some lesions can have large fibrous component
The presence of fat containing subcutaneous mass with intersecting bands of fibrous signal tissue in the appropriate age group is highly suggestive of the diagnosis. When closely apposed to the deeper muscle or fascial planes it may be difficult to differentiate from more aggressive soft tissue tumors.
Treatment and prognosis
Local excision is usually curative since recurrence is uncommon.
Differential diagnosis
Possible differential considerations include.
- benign
- malignant
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