Cervical lymphadenopathy secondary to rhabdomyosarcoma presenting as Horner syndrome in an infant.

A 4-week-old boy with left ptosis, anisocoria, and a mass on his left hand was diagnosed with Horner syndrome. The diagnosis precipitated a work-up for a possible malignant etiology. Magnetic resonance imaging demonstrated enlarged left cervical and axillary lymph nodes. A biopsy of the hand lesion confirmed embryonal rhabdomyosarcoma, but a biopsy of the axillary lymph node was negative. Mechanical pressure by noncancerous enlarged lymph nodes is hypothesized to cause the Horner syndrome.