The "botryoid sign": a characteristic feature of rhabdomyosarcomas in the head and neck

We investigated nine patients with rhabomyosarcoma in the head and neck (6- 53 years of age), using CT and MRI. The tumours originated in the paranasal sinuses (3), check (2), soft palate (1), orbit (1), sternocostoclavicular muscle (1) and parapharyngeal space (1). The histological subtype was embry onal in five, alveolar in three and pleomorphic in one case. The tumours en hanced markedly and heterogeneous on CT and MRI. The masses were isointense or gave slightly higher signal than surrounding muscles on T1- and heterog eneously high signal on T2-weighted images. In four tumours, multiple ring enhancement resembling bunches of grapes. This appears to be characteristic of rhabdomyosarcoma and probably reflects a component of botryoid-type rha bdomyosarcoma in which mucoid-rich stroma is covered with a thin layer of t umour cells. We have named this imaging feature the "botryoid sign".