Pathology of Lipofibromatosis

Dr Sampurna Roy MD                            2022

Lipofibromatosis is a rare pediatric lesion composed of abundant adipose tissue together with bundles of fibroblasts.

According to Fetsch et al - [ this tumour comprises part of the spectrum of what has been referred to in the literature as infantile/juvenile fibromatosis, its clinicopathologic features and, in particular, its distinctive tendency to contain fat as an integral component, warrant separate classification as a "lipofibromatosis."]

Age: 11 days to 12 years

Site:  The patients usually  presented with a soft tissue mass  involving upper and lower extremities, trunk , head or neck.

Microscopic features:

Two components:

1.Bundles of spindle shaped fibroblast-like cells with focal fascicular pattern

2. Disorganized mature adipose tissue.

The lesion mainly involved the septa of fat and skeletal muscle.

Mitotic activity is limited  - Less than 1/10HPF.

Cytological atypia is not prominent. 

The tumours entrapped vessels, nerves, skin adnexa and skeletal muscle.

Immunohistochemistry:  CD99 ; smooth muscle actin ; bcl2 - Focal Positivity  , S100 protein ; muscle actin ; EMA  - Less frequently positive ,  Desmin ; Keratins ; CD57 - Negative

Differential diagnosis:

-Fibromatosis;

-Fibrous hamartoma of infancy: In lipofibromatosis primitive nodular fibromyxoid component is absent. 

-Calcifying aponeurotic fibroma ;  Lipoblastoma