Soft tissue
Fibroblastic / myofibroblastic
Fibrous hamartoma of infancy
Author: Komal Arora, M.D.
Topic Completed: 1 July 2012
Minor changes: 4 January 2022
Copyright: 2002-2022, PathologyOutlines.com, Inc.
PubMed Search: Fibrous hamartoma of infancy
Table of Contents
Definition / general | Epidemiology | Sites | Case reports | Treatment | Clinical images | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosis | Additional referencesCite this page: Arora K. Fibrous hamartoma of infancy. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissuefibroushamart.html. Accessed January 19th, 2022.
Definition / general
- Tumor-like condition in newborns to 2 year olds
- Poorly circumscribed proliferation of immature spindle cells in organoid pattern with fat and dense fibrocollagenous tissue
Epidemiology
- Rare; usually age 2 years or less (25% discovered at birth), does not occur after puberty, 2/3 male
- Usually boys
Sites
- Axilla, shoulder and inguinal region (J Urol 1994;152:990)
- Not hands and feet
- Solitary, rapidly growing, freely movable mass of subcutis or dermis
Case reports
- 6 month old girl with fibrous hamartoma of infancy manifesting as multiple nodules with hypertrichosis (J Dermatol 2006;33:427)
- 6 month old boy with recurrent and synchronous fibrous hamartoma of infancy (Pediatr Surg Int 2005;21:119)
- 11 month old boy with fibrous hamartoma of infancy (The Internet Journal of Dermatology 2001;1(2))
- 4 year old boy with fibrous hamartoma of infancy in an unusual location (Gulf J Oncolog 2010;(8):52)
- 10 year old boy with fibrous hamartoma of infancy (Acta Derm Venereol 2005;85:276)
- Giant fibrous hamartoma of infancy (J Am Acad Dermatol 2011;64:579)
Treatment
- Benign, although may recur locally
- Excision, need not be aggressive as recurrence is uncommon (J Am Acad Dermatol 2006;54:800, J Korean Surg Soc 2011;81:61)
Clinical images
Images hosted on other servers:
Axillary tumor in 6 month old boy
Scapular tumor in 7 year old girl
Scapular tumor
at surgery
showing well
developed capsule
Gross description
- Poorly circumscribed, gray-white with yellow fat, usually 5 cm or less
Microscopic (histologic) description
- Poorly circumscribed, organoid with 3 components:
- Trabecular or stellate immature mesenchymal cells with scant cytoplasm and bland straight or wavy nuclei in myxoid matrix
- Fibrocollagenous tissue composed of bland fibroblasts or myofibroblasts
- Mature fat; overlying epidermis usually has eccrine changes, including hyperplasia, duct dilation, intraluminal papillary formations and squamous syringometaplasia (J Cutan Pathol 2007;34:39)
- No / scant mitotic figures
Microscopic (histologic) images
AFIP images
Primitive
spindle cells
may infiltrate fat
Triphasic
pattern of
fibrous
spindle cells
Primitive and
fibrous spindle
cells are bland
and uniform
Contributed by Mark R. Wick, M.D.
Images hosted on other servers:
Three cell types
Cytology description
- Moderate cellularity, adipose tissue fragments, clusters of fibroblastic cells, myxoid and collagenous matrix
- No mitotic figures, no atypia (Diagn Cytopathol 2003;28:272, Acta Cytol 2008;52:201)
Positive stains
Negative stains
Electron microscopy description
- Fibrous trabeculae are composed of fibroblasts and myofibroblasts, primitive mesenchymal cells have slender cytoplasmic processes with few organelles
Molecular / cytogenetics description
- EGFR exon 20 insertion / duplication mutations are characteristic (Am J Surg Pathol 2016;40:1713)
- Rarely complex translocations (Cancer Genet Cytogenet 2006;171:115, Cancer Genet Cytogenet 2010;201:66)
- Rarely t(2;3) (Arch Pathol Lab Med 2005;129:520)
Differential diagnosis
- Calcifying aponeurotic fibroma: almost always hands or feet, prominent calcification, no primitive cells within myxoid stroma
- Myofibroma: prominent hemangiopericytoma-like pattern, usually no fat
Additional references
