Secondary Leptomeningeal Sarcomatosis

A 4-year-old boy with a 1-year history of rhabdomyosarcoma of the nasopharynx and central skull base, who recently finished radiation therapy (total tumor dose of 4002 rads using 6-MV photons) and a course of chemotherapy (vincristine, actinomycin D, and cyclophosphamide), presented to the emergency department after his mother found him unresponsive. After admission, it was determined that he was in status epilepticus, which was refractory to intravenous anticonvulsants. Magnetic resonance imaging (Figure 1) showed a diffuse meningeal enhancement representing either infectious meningitis or metastatic disease. Examination of the spinal fluid revealed no evidence of neoplastic disease or infection. Imaging studies done 9 days after admission showed significant progression of his disease, with increased meningeal thickening and focal extension to the adjacent cortex and subcortical white mater. The patient died 14 days after admission, and an autopsy (limited to the brain) was performed.At autopsy, diffuse opacification of the meninges was grossly evident (Figure 2). There was cerebellar herniation and brain stem compression. Tissue sections revealed extensive involvement of the meninges and perivascular Virchow-Robin spaces by rhabdomyosarcoma (Figure 3, hematoxylin-eosin). Tumor invaded the parenchyma in multiple cerebral and brain stem sections. Tumor cells were strongly positive for desmin (Figure 4). Examination of the optic nerves revealed invasion of the subarachnoid and perivascular spaces, giving the cross-section a mosaic-like appearance (Figure 5, hematoxylin-eosin). Histologic and immunohistochemical findings were consistent with the original nasopharyngeal specimen.Rhabdomyosarcoma is the most common sarcoma of childhood. The incidence of rhabdomyosarcoma is highest in children ages 1 to 4 years; the rate falls by age 10 years and eventually levels off at ages 15 to 19 years. Embryonal rhabdomyosarcoma is the most common (75%) variant and has the highest incidence in children ages 1 to 4 years. Histologically, the tumor is composed of small, round, or spindle-shaped basophilic cells with occasional “strap cells.” Alveolar rhabdomyosarcoma is less common and presents throughout childhood. It consists of small, round to oval tumor cells that occur in nests separated by connective tissue septa. Twenty-three percent of primary rhabdomyosarcoma lesions have a parameningeal presentation.1The mosaic-like appearance of the optic nerves is caused by tumor involvement of the perivascular spaces, which separates the axons into bundles. The perivascular spaces are continuous with the space around the nerve, which is an extension of the subarachnoid space.Studies done by the Intergroup Rhabdomyosarcoma Study Group23 have shown that rhabdomyosarcoma arising in nonorbital parameningeal areas has a high probability of meningeal invasion. When meningeal involvement occurs after chemotherapy and radiation, the outcome is usually fatal.