Small Cell Mesothelioma

Small cell mesothelioma is an extremely rare subtype of mesothelioma. As the name suggests, cancerous cells in these tumors are smaller than cells in other forms of mesothelioma.

It is most commonly classified as a subtype of epithelial mesothelioma, but in one study of eight mesotheliomas with small cell features, only four were epithelial. The other four were biphasic, indicating a combination of both epithelial and sarcomatoid cells.

Small cell mesothelioma is much less common than other forms, such as adenomatoid mesothelioma or tubulopapillary mesothelioma. Less than Less than 6 percent of all mesothelioma tumors have a small cell pattern.

Most small cell mesothelioma tumors are not made up entirely of small cells. Instead, they often contain normal mesothelioma cells, small cell mesothelioma cells and other assorted neoplastic cells. Roughly half of all cells in the tumor should display a small cell pattern for the tumor to qualify as small cell mesothelioma.

Small Cell Mesothelioma Cells and Growth Patterns

Small cell mesothelioma cells are uniform in appearance. They are round and feature a single-bland nuclei that takes up the majority of the cell.

Small cell mesothelioma grows in a pattern that is similar to small cell carcinoma. However, small cell mesothelioma tumors do not display the stream, ribbon or rosette patterns that appear in small cell carcinoma. These tumors most commonly grow in the peritoneum, although they can also arise in the pleura or the pericardium.

Diagnosing and Treating Small Cell Mesothelioma

It can be challenging to correctly diagnose small cell mesothelioma. Small cell mesotheliomas can look very similar to other small cell neoplasms, and doctors must run immunohistochemical tests to differentiate between the diseases.

Illnesses that often resemble small cell mesothelioma:

• Metastatic small cell carcinoma
• Desmoplastic small round cell tumor
• Primitive neuroectodermal tumor
• Lymphoma

A single biopsy specimen may not always contain an accurate ratio of small cells. In one study, small cells made up 80 to 100 percent of the biopsy material, but after the only 15 to 20 percent of the full tumor. As a result, doctors may need to retrieve several samples to test for an accurate small cell mesothelioma diagnosis.

Once the samples undergo immunohistochemical staining, the different types of cells in the tumor all test positive for different compounds. Malignant small cell mesothelioma tests negative for several different neuroendocrine markers, such as CD56 and chromogranin.

Although there are too few cases of small cell mesothelioma to have a detailed standard of treatment, most doctors approach it the way they would approach any other type of mesothelioma. In a 2012 study of eight small cell mesothelioma patients, six patients passed away during the observation period. The mean survival of these patients was 8.2 months.