Embryonal malignancies of unknown primary origin in children

Background. Little is known about embryonal malignancies of unknown primary origin in children. All such cases referred to a pediatric cancer center over a 30‐year period were reviewed to delineate their clinical and prognostic features and to develop recommendations for evaluation and therapy. Methods. Seventeen patients with embryonal malignancies of unknown primary origin were identified by reviewing the institutional solid tumor database. The medical records, imaging studies, laboratory records, and pathology reports for each patient were reviewed and tabulated. Results. Pathology review confirmed the original histologic diagnosis in 15 of the cases. Final diagnoses after review were rhabdomyosarcoma (n = 9), neuroblastoma (n = 7), and Ewing's sarcoma (n = 1). At initial evaluation, an extensive array of radiologic studies revealed multiple abnormalities in 16 cases. Bone marrow sampling and urinary catecholamine analysis were valuable diagnostic tools. A primary site of origin was identified in five patients: by interval assessments during treatment in two cases, and at autopsy in three. Although the median survival was only 6 months, 3 patients are alive at 12,15 and 17 years after diagnosis. Conclusions. An exhaustive search for a primary lesion appears unwarranted in children with disseminated embryonal malignancies. Tumor sampling should be adequate for the pathologic work‐up to determine the definitive diagnosis. Although the chances of cure are slight, tumor specific therapy may improve the interval of disease control, the quality of life, and the possibility of long term survival.