Pleuropulmonary blastoma is a unique dysontogenetic neoplasm of childhood that appears as a pulmonary and/or pleural-based mass, and is characterised histologically by a primitive, variably mixed blastematic and sarcomatous appearance. We report a 12-month-old female child who was operated for a lung cyst at the age of six months and postoperative histopathology was suggestive of type I pleuropulmonary blastoma (PPB). She presented to us at the age of twelve months with a huge mass over the left chest wall and axilla, histopathological examination of which was type III PPB. Partial removal of the lung cyst led to transition from type I to type III PPB in a short span of a few months. Complete surgical removal followed by adjuvant chemotherapy is needed for a better outcome in type I PPB.