Sarcomatoid Characteristics and Subtypes
There are a few common characteristics of sarcomatoid cells:
- Sarcomatoid cells are long and are shaped like spindles.
- Sarcomatoid cells grow in a haphazard pattern, which allows them to spread faster than other mesothelioma cell types.
- How sarcomatoid cells spread makes them more resistant to treatment, contributing to a poor prognosis.
- Desmoplastic: Desmoplastic sarcomatoid cells are long and tend to look like bundles of collagen, a healthy protein found in the bones, muscle, tendons, and skin. At least half of a desmoplastic tumor will appear patternless, making it difficult to diagnose. Desmoplastic sarcomatoid cells account for about 5 percent of all mesothelioma diagnoses.
- Lymphohistiocytoid: Lymphohistiocytoid cells are large and shaped like spindles. They usually appear together with immune and inflammatory cells. The lymphohistiocytoid subtype accounts for less than one percent of all mesothelioma diagnoses.
- Transitional: Transitional sarcomatoid cells are plump and shaped liked spindles.
Specialists find it difficult to diagnose sarcomatoid cells due to their similarity to other cancer cells. Sarcomatoid tend to look like the benign tissue cells surrounding the tumor and to sarcomas, a form cancer that occurs in bone, muscle, or cartilage cells.
Sarcomatoid type mesothelioma is commonly misdiagnosed as:
- Sarcomatoid carcinoma
- Various sarcomas, such as synovial sarcoma, a cancer occurring near the arm, leg, or neck joints.
- Fibrous pleurisy
- Fibrous histiocytoma
A pathologist is a doctor who specializes in identifying cells to confirm a diagnosis. Pathologists use a technique called immunohistochemistry to apply special stains to samples taken from a biopsy. This technique helps them differentiate sarcomatoid cells from cells belonging to other cancers.
The stains they use contain markers, often proteins, that are attracted to certain cells. These markers attach themselves to cells, making them easier to see under a microscope. Pathologists can also identify sarcomatoid cells under a microscope by the absence of epithelial, or tissue, elements within the cell.
Markers for which sarcomatoid mesothelioma tests positive include:
- Cytokeratin: A protein found in epithelial tissue. Sarcomatoid mesothelioma cells usually contain cytokeratin, while most sarcomas do not.
- Podoplanin (D2-40): Through proposed by researchers as a positive marker, more studies must be completed to confirm its usefulness.
Sarcomatoid cell types are more resistant to treatment due to their haphazard spread pattern, rigidity, and aggressive metastasis (spread) to other parts of the body.
Surgery is most effective on patients with early-stage sarcomatoid mesothelioma because at this stage, the tumor has not yet spread to other parts of the body.
Removing advanced-stage pleural sarcomatoid tumors can be difficult. Sarcomatoid cells tend to spread into the chest wall, making surgery challenging at later stages. Sarcomatoid tumors in the abdomen are also difficult to remove due to their proximity the soft organs in the abdominal area.
Chemotherapy alone has not yet proven itself as an effective treatment for sarcomatoid type mesothelioma.
Studies have shown that select drugs have produced positive results when used to treat patients with sarcomatoid mesothelioma:
- Selenite: This mineral has been shown to inhibit the growth of sarcomatoid cells.
- Selenite with doxorubicin: Selenite amplifies the effect doxorubicin has on epithelioid cells. The combination of both drugs induced cell death (apoptosis) in the majority of treated cells.
- Cyclophosphamide, vincristine, adriamycin, and dacarbazine (CYVADIC): This chemotherapeutic treatment is a combination of four drugs, and has proven successful in treating soft cell cancers in a variety of clinical trials.
Patients diagnosed with sarcomatoid mesothelioma have a worse prognosis than patients with epithelioid or biphasic mesothelioma. The median survival rate for a sarcomatoid mesothelioma patient is 6 months after diagnosis. However, despite its negative prognosis, there is hope for patients with sarcomatoid mesothelioma.
Mesothelioma treatments are improving as clinical trials lead the way in advancements. Talk to a specialist to learn more about treatment options that can improve your prognosis.
- Roggli, V. L. Sarcomatoid mesothelioma: a clinical–pathologic correlation of 326 cases. Modern Pathology, 470-479. Retrieved July 7, 2014, from http://www.nature.com/modpathol/journal/v23/n3/full/modpathol2009180a.html.
- Lonardo, F. Sarcomatoid mesothelioma and its histological mimics: a comparative immunohistochemical study. Histopathology, 270-279. Retrieved July 7, 2014, from http://www.ncbi.nlm.nih.gov/pubmed/12605647.
- Dobra, K. Selenite induces apoptosis in sarcomatoid malignant mesothelioma cells through oxidative stress. Free Radical Biology and Medicine, 874-885. Retrieved July 7, 2014, from http://www.sciencedirect.com/science/article/pii/S0891584906003534.