Opsoclonus-myoclonus-ataxia syndrome in neuroblastoma: histopathologic features-a report from the Children's Cancer Group.

BACKGROUND: Opsoclonus-myoclonus-ataxia (OMA) is a paraneoplastic syndrome that occurs in about 2-3% of all cases of neuroblastoma. The histopathologic characteristics of neuroblastoma tumors associated with this syndrome were evaluated in a series of cases and controls. PROCEDURE: Pathology slides from a total of 54 neuroblastoma tumors were reviewed blindly. They included 13 tumors associated with opsoclonus-myoclonus and 41 age- and stage-matched controls. All tumors were classified into either the favorable (FH) or unfavorable histology (UH) group according to the International Neuroblastoma Pathology Classification (the Shimada system). Grade of lymphocytic infiltration was evaluated and presence or absence of lymphoid follicles was recorded in the individual tumor tissues. RESULTS: Twelve of 13 cases with opsoclonus-myoclonus were in the FH group. Twelve of 13 cases had diffuse (found in every section prepared from the multiple portions of the primary tumor) and extensive (occupying more than 50% of a single of multiple microscopic fields with x 100 magnification) lymphocytic infiltration with lymphoid follicles. Of the 41 control cases (27 FH and 14 UH tumors), 18 had focal areas of lymphocytic infiltration and six showed lymphoid follicles, but none had diffuse or extensive infiltration in their primary tumors. CONCLUSIONS: Diffuse and extensive lymphocytic infiltration with lymphoid follicles is a characteristic histologic feature of neuroblastic tumors with opsoclonus-myoclonus. This observation suggests an immune-mediated mechanism for this rare paraneoplastic syndrome.