Metastatic Sarcomatous Tumor to Mandible Identifies Pleuropulmonary Blastoma Tumor Predisposition Syndrome

Abstract

<h3>Introduction</h3> Pleuropulmonary blastoma (PPB) affects infants and young children and may occur as a cystic (Type I), partially cystic-partially solid (Type 2), or solid (Type 3) tumor. PPB is an embryonal tumor derived from lung and pleural mesenchyme. This malignant tumor is composed of sarcomatous elements, most commonly a mixture of spindle cell sarcoma with focal rhabdomyosarcomatous elements. However, it may have a wide variety of sarcomatous components. The tumor is characterized by DICER1 mutation, which may be somatic (tumoral) or constitutional. Constitutional DICER1 mutation indicates a predisposition for the development of other tumors and may have implications for the child and other family members. <h3>Clinical Presentation and Pathology Findings</h3> This 18 month-old male presented with a rapidly enlarging, expansile left mandibular mass. A biopsy was performed which showed a predominantly spindle cell sarcoma (vimentin-positive) with focal areas of readily identified rhabdomyoblasts (positive for desmin; negative for myogenin and MyoD1. Molecular genetic testing of the tumor identified a DICER 1 mutation and was negative for rearrangements associated with rhabdomyosarcoma (FOXO1, FUS-TFCP2, EWSR1-TFCP2, NCOA2, VGLL2). Radiologic workup identified a predominantly solid pulmonary mass. Lobectomy was performed and diagnosis of PPB was confirmed. Sarcoma-based oncologic management was carried out. Subsequent genetic testing identified DICER1 constitutional mutation. <h3>Conclusion</h3> PPB presenting as a metastatic disease is not unusual, with the involvement of various sites and organs (most common sites: brain, bone). Although exceedingly rare, PPB should be considered in an infant or young child when encountering a possible metastatic sarcomatous tumor and prompts radiologic evaluation for a possible primary lung tumor. Molecular genetics plays an essential role in identifying risk for PPB Tumor Predisposition Syndrome. Oncologic management is sarcomabased and children with isolated lung tumors have variable outcomes (Type I - 85%, Type 2 - 60%, Type 3 - 40%).