Congenital alveolar rhabdomyosarcoma: clinical and molecular distinction from alveolar rhabdomyosarcoma in older children

Background: Congenital alveolar rhabdomyosarcoma (RMS) is extremely rare and invariably fatal with current therapy. Its clinical presentation is unusual and is distinct from RMS in older children, with > 50% of patients presenting with multiple cutaneous metastases. To the authors' knowledge, the biology of this condition has not been studied to date.

Methods: The clinical and pathologic findings of four cases of congenital RMS are presented along with those of other cases found in the literature. Molecular analysis was undertaken to detect the characteristic chromosomal translocations of alveolar RMS in three cases with suitable material.

Results: To the authors' knowledge, there are no recorded survivors of congenital alveolar RMS. Clinical and histopathologic findings in four patients with congenital alveolar RMS are detailed along with treatment responses. It now is recognized that tumor specific translocations can be detected in the majority of cases of alveolar RMS using the reverse transcriptase-polymerase chain reaction (RT-PCR) method. However, detailed molecular analysis using RT-PCR was unable to detect the presence of either the classic t(2;13) or variant t(1;13) translocation in three cases analyzed at the molecular level.

Conclusions: To the authors' knowledge the optimal treatment for this rare tumor is not known. The longest survivor in the current series underwent myeloablative therapy with peripheral stem cell support, suggesting that more intensive treatment may be of value in this rare condition. None of the three tumors analyzed by RT-PCR harbored characteristic RMS translocations. The molecular biology of this highly malignant and aggressive congenital tumor appears to be different from alveolar RMS in older children and warrants further investigation.