A recent study published in the British Journal of Cancer compared survival rates of mesothelioma patients that received their diagnosis through either cytological or by histological method for those with the epithelioid, biphasic, or sarcomatoid subtype of mesothelioma. The concern is that those with the biphasic subtype of mesothelioma are under diagnosed when epithelioid mesothelioma is diagnosed using cytology.
- Epithelioid – Most common subtype of mesothelioma. Epithelioid cells are easily defined based upon their distinct, elongated egg-shape. While epithelioid cells do divide faster than other cells, the cells typically stick together, so the cancer does not spread as quickly, making it the most treatable form of mesothelioma.
- Sarcomatoid – Least common subtype of mesothelioma and also harder to diagnose because the spindle-shaped cells have multiple nuclei. Unlike epithelioid cells, sarcomatoid cells do not stick together, which allows for the cancer to spread quickly to other areas of the body.
- Biphasic – Second most common subtype of mesothelioma that is made up of both epithelioid cells and sarcomatoid cells. Epithelioid and sarcomatoid cells are often not equally present in the biphasic subtype, so prognosis is based upon which cell is more prevalent. Biphasic tumors with more epithelioid cells typically result in a better diagnosis.
Cytological and histological diagnoses
Cytology-based diagnosis means that single cells and small clusters of cells are investigated to determine different types of cancer. Cytology tests are similar to biopsies, but explore the fluids in different cavities in the body rather than retaining a tissue specimen. Cytology specimens typically cost less, is easier to produce, and is less likely to cause the patient any discomfort. However, biopsies tend to be more accurate.
When determining the subtype of mesothelioma, tissue samples that contain the cancer are extracted from the patient and examined under a microscope. This process is called histology, and is an essential part in determining the subtype of mesothelioma: epithelioid, biphasic, and sarcomatoid. A histology report is imperative when defining any type of cancer because it gives a more accurate diagnosis and prognosis.
To determine which diagnosis resulted better survival rates for mesothelioma patients, scientists and researchers examined records from the Western Australia Mesothelioma Registry. These records showed 2,024 malignant mesothelioma cases over the span of 42 years. Epithelioid subtype accounted for 59% of the cases, with 41.2% being diagnosed through cytology-only method. With age factored in, average survival rates for cytological and histological diagnoses were similar (cytology 5.5 -19.2 months, histology 4.8-19.8 months). These results show that the diagnostic methods do not have an impact on survival.
Muruganandan S, et.al., “Comparison of Outcomes Following Cytological or Histological Diagnosis of Malignant Mesothelioma,” British Journal of Cancer (2017 March 14). [Link]
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