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.
There is a reported male:female ratio of 2:1 but the exact incidence is unknown 2.
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.
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.
- heterogenous hyperechogenecity
- serpentine intervening hypoechoic portions
- margins well defined or lobulated
- vascularity is minimal if present
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.
Possible differential considerations include.
- 1. Laffan EE, Ngan BY, Navarro OM. Pediatric soft-tissue tumors and pseudotumors: MR imaging features with pathologic correlation: part 2. Tumors of fibroblastic/myofibroblastic, so-called fibrohistiocytic, muscular, lymphomatous, neurogenic, hair matrix, and uncertain origin. (2009) Radiographics : a review publication of the Radiological Society of North America, Inc. 29 (4): e36. doi:10.1148/rg.e36 - Pubmed
- 2. Saab ST, McClain CM, Coffin CM. Fibrous hamartoma of infancy: a clinicopathologic analysis of 60 cases. (2014) The American journal of surgical pathology. 38 (3): 394-401. doi:10.1097/PAS.0000000000000104 - Pubmed
- 3. Lee S, Choi YH, Cheon JE, Kim MJ, Lee MJ, Koh MJ. Ultrasonographic features of fibrous hamartoma of infancy. (2014) Skeletal radiology. 43 (5): 649-53. doi:10.1007/s00256-014-1838-1 - Pubmed
- 4. Stensby JD, Conces MR, Nacey NC. Benign fibrous hamartoma of infancy: a case of MR imaging paralleling histologic findings. (2014) Skeletal radiology. 43 (11): 1639-43. doi:10.1007/s00256-014-1940-4 - Pubmed