Sarcomatoid Carcinoma

Fabio R. Tavora, M.D., Ph.D.

Marie-Christine Aubry, M.D.

Allen P. Burke, M.D.

Terminology

Sarcomatoid carcinoma of the lung designates a poorly differentiated and aggressive neoplasm with both carcinoma and mesenchymal differentiation. The epithelial component can be adenocarcinoma, squamous cell carcinoma, or undifferentiated non-small cell carcinoma (i.e., large cell carcinoma). The mesenchymal component is characterized morphologically by spindle cell, giant cell, or sarcoma with heterologous elements such as rhabdomyosarcoma, chondrosarcoma, and osteosarcoma.

If the mesenchymal component is either spindle cell or giant cell, the tumor is designated as pleomorphic carcinoma, while tumors with chondro-, osteo-, or rhabdomyosarcomatous elements are called carcinosarcomas. If a tumor is composed almost entirely by spindle cell or giant cell with no differentiated carcinomatous components, the tumors can be classified as spindle cell carcinoma and giant-cell carcinoma, respectively.

Small cell and large-cell neuroendocrine carcinomas with undifferentiated spindled areas are extremely rare.¹^,²

The 2015 WHO classification of lung tumors recommends that at least 10% of each component (epithelial and mesenchymal) should be present in order to make the diagnosis.³

A third subtype of sarcomatoid carcinoma is pulmonary blastoma, defined as a biphasic tumor with components of fetal adenocarcinoma and primitive mesenchymal stroma. Pleuropulmonary blastoma is covered in Chapter 96 and fetal adenocarcinoma in Chapter 77.

Although debated over years, it is now accepted that sarcomatoid carcinomas, including carcinosarcoma, are clonal tumors arising from an epithelial origin.⁴^,⁵

Incidence

Approximately 0.5% of lung tumors are sarcomatoid carcinomas and, of those, only about 5% are carcinosarcomas.⁶^,⁷^,⁸^,⁹^,¹⁰^,¹¹^,¹²^,¹³^,¹⁴^,¹⁵ Pulmonary blastomas are even less common, accounting for <0.1% of lung tumors.³^,¹⁶

Clinical Presentation

Sarcomatoid carcinomas occur in an older population compared to other conventional non-small cell carcinomas, mainly male smokers.⁶^,⁹^,¹⁵^,¹⁷ Symptoms are similar to other tumors and include cough, hemoptysis, and thoracic pain. The clinical behavior of these tumors is aggressive with a short overall survival rate, even for early-stage tumors, and a high rate of regional and distant metastases.⁶^,⁹^,¹⁵^,¹⁸ Metastases to unusual sites such as the small intestine have been reported.¹⁹

TABLE 85.1 Morphologic Features Sarcomatoid Carcinoma Subtypes

Histologic Type	Epithelial Component	Mesenchymal Component	Immunohistochemistry
Pleomorphic carcinoma	Adenocarcinoma, squamous cell carcinoma, large cell carcinoma, and adenosquamous carcinoma	Spindle cell or giant cell with at least 10% of the tumor	CK, EMA, and CEA + Vimentin + Actin +/- TTF-1 +/-
Spindle cell carcinoma	No distinct epithelial component	Spindle cell	CK, EMA, and CEA +/- Vimentin + Actin + TTF-1 -/+
Giant-cell carcinoma	No distinct epithelial component	Giant cell	CK, EMA, and CEA +/- Vimentin + Actin + TTF-1 –
Carcinosarcoma	Adenocarcinoma, squamous cell carcinoma, large cell carcinoma, and adenosquamous carcinoma	Rhabdomyosarcoma, osteosarcoma, chondrosarcoma, and liposarcoma	CK, EMA, and CEA +/- Vimentin + Actin +/- TTF-1 – Desmin + in rhabdomyosarcoma S100 + in chondrosarcoma
Pulmonary blastoma	Fetal adenocarcinoma usually with low-grade features	Primitive mesenchymal stroma with occasional rhabdomyosarcomatous or osteosarcomatous differentiation	CK, EMA, and CEA +/- Vimentin + Actin + TTF-1 + Chromogranin + Desmin + in rhabdomyosarcoma S100 + in chondrosarcoma β-catenin +

Patients with pulmonary blastomas are typically adults, with an average age of 40.²⁰ Over 80% of patients have a smoking history. They usually present as a large chest mass causing pain, hemoptysis, cough, and dyspnea. The tumor may be an incidental finding in up to 40% of patients.²¹

Pulmonary blastomas are quite aggressive and often metastasize to the central nervous system, as well as unusual locations, such as spleen and axilla.²²^,²³^,²⁴ Mean survival is 33 months, with a poor response to chemotherapeutic agents.²⁰

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