20 January 2010 – Case of the Week #166
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Case of the Week #166
An eight month old infant presented with difficulty in feeding and shortness of breath. X-ray findings showed a right upper lobe lung mass.
The mass was a large, solid, firm, whitish-gray lobulated tumor measuring 13 x 8 x 7 cm and weighing 280 gm. Cut sections showed foci of necrosis and cystic spaces.
What is your diagnosis?
Type III pleuropulmonary blastoma
Microscopically, the tumor was composed of primitive, undifferentiated blastema cells and sarcomatous elements of different types of differentiation, including lipoblastic, chondroblastic, rhabdomyoblastic and giant cell undifferentiated sarcomas. Cystic and slit-like spaces lined by the primitive or sarcomatous cells were identified. Multiple foci of necrosis were present. These features are consistent with type III pleuropulmonary blastoma.
(PPB) is a childhood tumor of the lung or pleura that usually occurs in
children age 4 years or younger. Although rare overall, it is one of the
most common primary lung malignancies in children (Arch Pathol Lab Med 2008;132:1079), and an international registry is at http://www.ppbregistry.org.
It was first described in 1988 (Cancer 1988;62:1516), and is classified into three types:
Type I is multicystic, and may progress into types II or III.
Type II shows thickened areas within the cysts.
Type III shows solid masses.
Children usually present with difficulty breathing or other respiratory problems. MRI or CT can help diagnose, though biopsy is suggested (Pediatr Radiol 2007;37:337). Microscopically, PPB shows mixed blastematous and sarcomatous appearance and primitive cells (Singapore Med J 2007;48:e190).
The differential diagnosis for type III cases is broad, because of the histologic variability. Many tumors may resemble embryonal rhabdomyosarcoma, but PPB also has cystic architectural, blastema tissue and other mesenchymal components such as cartilage. In addition, primary pulmonary or pleural rhabdomyosarcoma is extremely rare. Other tumors to consider include monophasic synovial sarcoma, malignant peripheral nerve sheath tumor, mesothelioma, malignant teratoma and undifferentiated sarcoma. Immunostains are typically not helpful in differentiating these entities. A recent finding that may prove helpful is the frequent presence of gains in chromosome 8q in PPB (Mod Pathol 2007;20:1191).
Treatment is radical
surgery to excise the cyst or mass, with extensive follow up to detect
relapses. Chemotherapy is usually provided for types II and III.
Half of patients eventually develop cerebral metastases (Pediatr Blood Cancer 2007;49:266).
Additional references: J Pediatr Oncol Nurs 2008;25:295
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