Pulmonary blastoma is a rare aggressive neoplasm comprising 0.25-0.5%
of all primary lung tumours.
Morphologically this tumour mimics fetal lung tissue before 4 months
Pulmonary blastoma was first described by Dr W G Barnard at St
Thomas's Hospital- London in 1952.
He called this
unusual tumour "Embryoma of Lung" based on the histological
resemblance of the tumour to fetal lung tissue.
term blastoma was introduced in 1961 by Spencer who described the
tumour origin from a pleuripotential pulmonary blastoma analogous to
Wilm's tumor that appears to share the same histological features.
Historically, the term pulmonary blastoma had included three
subgroups: classic biphasic pulmonary blastoma, well-differentiated
fetal adenocarcinoma - also called monophasic pulmonary blastoma- and
pleuropulmonary blastoma of childhood.
fetal adenocarcinoma consists of epithelial malignant component only;
the classic biphasic pulmonary blastoma is characterized by both
epithelial and mesenchymal malignant components; pleuropulmonary
blastoma, that is, a childhood tumour shows features of mesenchymal
malignant components only.
Recent World Health Orgnisation (WHO) reclassifications, separated
well-differentiated fetal adenocarcinomas and pleuropulmonary
blastomas from the classic biphasic tumours.
Clinically, the patient typically presents with cough, hemoptysis,
dyspnea or chest pain due to tumour impinging on the bronchi or
pleura. Forty percent of cases may be asymptomatic. The average age at
diagnosis is 40 years with an increased frequency in males.
Pulmonary blastomas are biphasic tumours that are part of the
sarcomatoid carcinoma subgroup, which also include carcinosarcomas
(defined as a malignant tumour having a mixture of carcinoma- and
sarcoma-containing heterologous elements such as malignant cartilage,
bone, or skeletal muscle) and pleomorphic carcinomas (similar tumour
without heterologous elements), both histologically resembling
adult-type carcinomas and sarcomas.
Classic biphasic blastoma has distinctive
The epithelial component
of classic biphasic blastoma is composed of tubules of glycogen-rich,
non-ciliated cells that resemble fetal lung of pseudo-glandular stage
of lung development with sub-nuclear and supra-nuclear glycogen
appearance of the stroma is due to the small size, oval and spindle
shape of the cells, and myxoid matrix. Classically this blastematous
stroma does not express cytokeratins or pulmonary markers.
The tumour has a poor prognosis.
Two thirds of
patients die within 2 years and only 16% patients have 5-year
survival. Prognosis is determined by size of the tumor at time of
diagnosis, with tumors <5 cm doing better. Tumour metastasis and tumor
recurrence despite resection both predict a poor prognosis.