Sarcomatoid/Spindle Cell Carcinoma of the Lung
Thomas V. Colby
(Case courtesy of Dr. G.H. Faber, Parkersburg, WV)
78 year old man with a 35 pack year smoking history was found to have a left apical mass on chest imaging
studies. He came to lobectomy.
Necrotic cellular mass with abnormal appearing small vessels in the adjacent lung tissue
Detail of the spindle cell proliferation comprising the mass
Detail of the spindle cell proliferation comprising the mass
Involvement of a relatively large pulmonary artery branch
High power of luminal proliferation seen in Figure 4
Small vessels in the lung tissue surrounding the mass
High power of the vessels shown in Figure 6
Small vessels in the lung tissue surrounding the mass
High power of the vessels shown in Figure 8
Sarcomatoid/spindle cell carcinoma of the lung.
The patient died of his lung cancer one year later.
Lung cancer, carcinoma of the lung, sarcomatoid carcinoma of
the lung, sarcoma of the lung, spindle cell carcinoma of the lung, carcinosarcoma of the lung.
- Sarcomatoid/spindle cell carcinomas
of the lung may be mistaken for sarcomas or reactive processes
- Many previously reported "sarcomas" of the lung (and
probably all carcinosarcomas) were sarcomatoid carcinomas.
- Synovial sarcoma is probably the most common sarcoma
encountered in the lung in current practice (but these were not recognized until the 1990's).
- Sarcomatoid carcinomas account for 1-5% of lung cancers.
- Sarcomatoid carcinomas represent a subset of non-small
cell lung cancers.
- Sarcomatoid carcinomas have a worse prognosis than other
non-small cell lung carcinomas.
- The "sarcomatoid" regions of sarcomatoid carcinomas are
thought to derive from the same clonal population of cells as the carcinomatous components (when
carcinomatous areas are present) and this is thought to reflect epithelial mesenchymal transformation.
Sarcomatoid Carcinomas of the Lung
Sarcomatoid carcinomas mimic sarcomas because of the presence of spindle cells or matrix
production/mesenchymal differentiation (or both). Depending on the patterns present terms such as
spindle cell carcinoma and carcinosarcoma have been used. Differentiated mesenchymal elements
encountered include rhabdomyosarcoma, osteosarcoma, chondrosarcoma, and rarely liposarcoma.
With the development of immunohistochemical stains to recognize epithelial differentiation, the number
of sarcomas reported in the lung has greatly decreased and, with the exception of synovial sarcoma, there
have been few series of lung sarcomas since the 1980's. Nevertheless it is still said that one may
encounter virtually any sarcoma in the lung, albeit rarely and in the 2008 review by Litzky the following
Leiomyosarcoma, Synovial sarcoma, Malignant peripheral nerve sheath tumor, Malignant solitary fibrous
tumor, Epithelioid hemangioendothelioma, Angiosarcoma, Kaposi sarcoma, Inflammatory myofibroblastic
tumor, Chondrosarcoma, Osteosarcoma, Liposarcoma, Fibrosarcoma, MFH, Hemangiopericytoma
Pulmonary artery and vein sarcomas could be in this list as well. Surprisingly, synovial sarcoma,
which is one of the most common, if not the most common sarcoma encountered in the lung, was not
recognized until 1995.
Cases with a large component of conventional carcinoma the diagnosis is relatively easy; cases in which carcinomatous elements are absent or inconspicuous present a diagnostic
Clues to spindle cell/sarcomatoid carcinoma include the following:
Because of the various growth patterns individual cases may mimic an abscess or organizing pneumonia:
so-called inflammatory sarcomatoid carcinoma. A myofibroblastic appearance to
the tumor cells may mimic inflammatory myofibroblastic tumor. Some cases produce spaces resembling blood
vascular spaces: so called pseudoangiosarcomatous sarcomatoid carcinoma.
Immunohistochemistry is straightforward when there is a recognizable
differentiated carcinomatous element present. Mesenchymal element show the typical staining pattern of
that sort of differentiation. Problems with immunohistochemistry may be encountered when there is a pure
spindle cell component. When this component is diffusely and strongly positive for epithelial markers
the diagnosis is easy. Some cases show only spotty positivity and there may be large regions of the
tumor (sometimes several blocks) that are negative for epithelial markers. When a sarcomatoid carcinoma
is suspected one should try a number of epithelial markers such as AE1/AE3, CAM5.2, EMA, CEA and others.
In some cases only one or two markers show appreciable positivity.
Because epithelial differentiation may be only focal either on the histology or immunohistochemistry,
sampling is important in these lesions.
Epithelial differentiation may also be documented with electron microscopy but in most laboratories
immunohistochemistry has replaced electron microscopy in routine practice.
- Sarcomatoid carcinomas are probably the most common malignancy
encountered in the lung with a population of spindle cells (i.e. high pretest probably of sarcomatoid
- Sarcomatoid carcinomas generally do not look like typical soft
- The nuclear features are more typical of carcinoma.
- Sarcomatoid carcinomas have a marked propensity for vascular
- Sarcomatoid carcinomas may show interstitial growth and
surround alveolar spaces lined by reactive Type 2 cells.
Sarcomatoid Carcinomas in the WHO Classification
In the 2004 WHO classification of lung tumors the following were included under the category
By convention an individual component must involve at least 10% of a given tumor in order for the
designation to apply. Sarcomatoid carcinomas composed entirely of spindle cells (spindle cell carcinoma)
pose the greatest difficulty in separation from sarcoma. This spindle cell component in spindle cell
carcinomas may show some positive staining with actin, desmin, and S-100.
- Pleomorphic carcinoma
- Spindle cell carcinoma
- Giant cell carcinoma
- Pulmonary blastoma
Clinical Aspects of Sarcomatoid Carcinomas of the Lung
Sarcomatoid carcinomas account for 1-5% of all lung cancers. 90% of the patients are
smokers and the median age is ~ 60 years. Men are affected more often than women (with ratios
varying from slightly greater than 1:1 to 10:1 in various series). While one or two series suggested
that the prognosis was similar to that of other small cell lung cancers, stage for stage, most recent
series suggest that this form of lung cancer is a particularly aggressive and the prognosis is worse
stage for stage than other non-small cell lung cancer.
Sarcomatoid carcinomas represent variants of non-small cell lung cancer and
should be managed as such. As with lung cancer in general it is important in such cases to identify
whether there is any squamous or glandular differentiation (TTF-1, CK 5/6, p63 staining); in individual
cases other studies, including molecular studies (EGFR, K-ras, RRM1, ERCC1,
BRCA) may be requested to guide therapy.
Sarcomatoid Carcinomas of the Lung - Histogenesis
As in other organ systems that show tumors with divergent histology, it is currently accepted that
sarcomatoid carcinomas in the lung, including those with both carcinomatous and sarcomatous elements,
represent malignancies of a single clone showing divergent
differentiation. Methods to confirm have included allelotyping, K-ras mutational genotyping, and
comparative genomic hybridization. Indeed one can often encounter histologic, immunoistochemical, and
electron microscopic transitions between cells showing epithelial features and those showing mesenchymal
features. These tumors are thought to reflect an epithelial mesenchymal transformation.
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