Intra-abdominal Solitary Myofibroma in a Child: A Rare Case Report

Abstract

Intra-abdominal masses in children are usually malignant. Benign tumours at this location are not seen frequently. It is even rarer to find solitary myofibromas intra-abdominally as these tumours are known to have predilection for the head and neck region. We present an unusual case of solitary myofibroma with abdominal localisation in a six-year-old male child who presented with abdominal distension since six months. Computed Tomography (CT) abdomen revealed a complex solid-cystic mass extending from umbilicus to right iliac fossa and measuring 9×6×4 cm. Histopathological examination revealed a tumour displaying biphasic nodular pattern with the presence of lighter staining fascicles of mature myoid cells along with darker staining and more cellular areas of smaller primitive cells. On Immunohistochemistry (IHC), tumour cells were positive for vimentin and Smooth Muscle Actin (SMA) with variable reactivity for desmin while these were negative for CD34 and Anaplastic Lymphoma Kinase 1 (ALK). Based on the histopathological and immunohistochemical findings, final diagnosis of myofibroma was made. Recognition of these lesions is extremely challenging owing to their rare presentation intra-abdominally and also because of their close morphological overlap with other spindle cell tumours commonly found at this site. This case highlights the combined role played by histopathology and IHC in making a clear distinction between different entities. It is imperative for both clinicians and histopathologists to establish the correct diagnosis as excision of the solitary myofibroma is curative in most cases and offers better clinical course than the more commonly found malignant tumours at this site.