Spindle Cell/Sclerosing Rhabdomyosarcoma : Introduction
Introduction: Spindle cell and sclerosing rhabdomyosarcomas (RMS) were previously considered separate entities. However, they are now thought to be related based on overlapping morphologic as well as molecular genetic features (MYOD1 mutations). They are grouped together as spindle cell/sclerosing RMS in the new WHO Classification. They are uncommon neoplasms and account for 5% to 10% of all RMS. All age groups are affected, although the initial cases were reported in children. There is a striking male predilection. In the pediatric variant, the mean age at diagnosis is 7 years. The most common site of involvement is the paratesticular region followed by the head and neck region. It carries a favorable prognosis. Spindle cell variant of RMS in adults, however, shows predilection for head and neck region and extremities, has greater cytologic atypia, and is more aggressive than pediatric lesions. The image shows spindle cell/sclerosing RMS in an adult. The degree of cellularity and the lack of collagenous stroma creates an appearance resembling fibrosarcoma.