Desmoid tumour: a rare cause of congenital unilateral calf enlargement mimicking calf hypertrophy.

Desmoid tumours, also known as aggressive fibromatosis, are rare tumours derived from mesenchymal stem cells, accounting for only 0.03 % of all tumours. While 85-90 % of cases are sporadic, desmoid tumours can occasionally be associated with Gardner syndrome (or Familial Adenomatous Polyposis), which is linked to variants in the tumour suppressor gene, APC (adenomatous polyposis coli) gene on chromosome 5. We describe a paediatric patient with congenital unilateral calf enlargement who was diagnosed as fibromatosis confirmed by muscle biopsy. Genetic workup was unrevealing, and muscle biopsy confirmed the diagnosis of fibromatosis. APC gene mutations were negative in this patient. Fibromatosis is a rare diagnosis which may have implications for the whole family and may present with congenital calf enlargement.