Myofibroblastoma of Axillary Soft Tissue in a Child

Aims: Myofibroblastoma (MFB) is an unusual benign mesenchymal tumour which has neoplastic cells showing a variable myofibroblastic differentiation at morphologic, immunohistochemical and ultrastructural levels. MFB is commonly seen in adult population with age range of 36-67 years. This tumour is very rare in paediatric population with few reported cases below the age of 21 years. We report myofibroblastoma in a youngest female child which mimicked a malignant tumour.

Presentation of Case: A four-year-old female child with history of tender left axillary swelling since one year. The swelling was initially small and gradually increased to present 8 x 6 cm size. The lump was oval, firm to hard, mobile, tender with clear margins and smooth surface. MRI studies of the left shoulder and thorax revealed enhancing neoplastic mass in the left axilla inseparable from the subscapularis muscle measuring 8 x 5 x 6 cm. Grossly the tumour measured 8 x 5 x 6 cm, was well-circumscribed and partially encapsulated with solid, grayish-white to tan appearance. The overall features favoured the diagnosis of myofibroblastoma.

Discussion: Myofibroblastoma is a benign mesenchymal tumour commonly involving breast in elderly males. Extra-mammary location is very rare for this tumour with few reported cases. In English literature only six cases have been reported below 21 years of age and all were teenagers. The prior youngest reported case was in a nine-year-old girl with left groin swelling.

Conclusion: Extra-mammary myofibroblastoma is a rare entity and is uncommon in paediatric population below the age of five years.