Lymphohistiocytoid Mesothelioma

What Lymphohistiocytoid Mesothelioma?

Lymphohistoicytoid mesothelioma is an aggressive sarcomatoid cell type. These tumors tend to have a mix of epithelioid cells and inflammatory cells. Some patients with this subtype may have an optimistic prognosis, like an epithelial cell diagnosis.

There are few reported cases of this subtype. Doctors often misdiagnose it as another condition, often non-Hodgkin’s lymphoma. Symptoms and treatment options mirror those of other pleural mesothelioma types. Its rarity leaves researchers few opportunities to study it, and there is little information for review. Pathologists have identified specific tumor characteristics that can aid in an accurate diagnosis.

Diagnosing Lymphohistiocytoid Mesothelioma

First, surgeons take a sample of the tumor during a biopsy. Then, they send it to a lab for a pathological study. Many of the immune cells found in this subtype mimic other cancers. This can lead to misdiagnosis.

Under a microscope, histological studies reveal large, atypical polygonal to spindle-shaped histiocytoid cells. Mixed with these cells are white blood cells.

Other signs of this tumor type are:

• Diffuse pleural thickening
• Small nodules throughout the pleura (the lining of the lung)
• Pleural effusion (a fluid buildup between pleural layers)

In this type of mesothelioma, histological studies and visual presentation of pleural-tissue changes are not usually enough to make a firm diagnosis. For a definitive diagnosis of lymphohistiocytoid mesothelioma, an immunohistochemical panel of antibodies for pathological staining is mandatory so that tumors can be differentiated from others that are similar.

In immunohistochemistry, pathologists add antibodies to tumor tissue. These stain the tissue when there is a positive reaction. Each cancer has certain positive markers. Seeing them under a microscope can help make a more accurate diagnosis.

To prepare a sample, the pathologist fixes tumor tissue in a paraffin block. They then trim the block into thin slices and mount them on a slide. In studies, these tumor cells expressed cytokeratin, vimentin, calretinin and CH5/6. They were negative for lymphoid and macrophage markers. AE1/AE3 and calretinin antibodies are the most reliable for staining tissue samples.

Symptoms, Treatment and Prognosis of Lymphohistiocytoid Mesothelioma

Symptoms are like other types of pleural mesothelioma. They may include:

• Chest pain
• Weight loss
• Fatigue

Treatment information is limited for this type. Patients generally receive surgery, chemotherapy and radiation therapy.

Early cases in a 1988 report showed no positive response to chemotherapy or radiation. The three patients in the report survived between four and eight months. A 2007 study evaluated 22 cases. This study showed improvement and a positive response to treatment. Patients had extended life spans. Their survival ranged between 32 and 40 months after diagnosis.

One encouraging case study showed a spontaneous regression of the tumor. Doctors removed tumors from the patient via surgery. The patients remained alive and without symptoms for 12 years after the initial presentation. In a small number of studies, some patients survived as much as six years after diagnosis. Doctors suggest that immune cells in this tumor may contribute to spontaneous regression.