Case report of pleuropulmonary blastoma: The heterogenous features of a rare primitive neoplasm of the thorax

Introduction: Pleuropulmonary blastoma (PPB) is a rare primary neoplasm of the thorax frequently diagnosed in early childhood. Pleuropulmonary blastoma arises from primitive intrathoracic mesenchyme—either pulmonary and pleural, or both. Patients with pleuropulmonary blastoma usually present with respiratory symptoms and are often misdiagnosed as pneumonia in the early clinical course. Pleuropulmonary blastoma can be further classified into types I, II, and III based on histological components. Such histological distinctions have significant implications for the treatment of these lesions as well as prognosis. Currently, the treatment of pleuropulmonary blastoma is surgical resection with or without chemotherapy, based on the histological type. Case Report: We highlight the histopathological presentation of pleuropulmonary blastoma in a 3-year-old male who presented with nonspecific symptoms. After identifying an intrathoracic mass on imaging, frozen section demonstrated primarily mature cartilaginous tissue without rhabdomyosarcomatous differentiation or anaplasia. Surgical resection specimens, however, contained small areas of proliferating spindle cells with skeletal muscle features as well as primitive blastema-like cells. Following ancillary testing, the patient was diagnosed with a type II PPB. Conclusion: This case illustrates the challenges of using frozen sections to diagnose heterogenous neoplasms such as PPB. The histologic features of this patient’s tumor identified on frozen section were largely mature and benign-appearing. Only when considering the histology of the surgical specimens in combination with immunohistochemistry and gross morphology, we were able to make an accurate assessment about the type of PPB and corresponding prognosis and treatment plan. Therefore, we urge pathologists to consider PPB for large thoracic masses in pediatric patients.