To assess the differences between thymoma patients with/without myasthenia all of their characteristics must be considered

Sir,

We read with interest Al Shammari et al.’s article on a retrospective, single-center study on the clinical, demographic characteristics, and prognostic impact of myasthenia gravis (MG) in thymoma patients who underwent surgical resection of thymoma over the past 23 years.[1] Seventy thymoma patients were included, 39 of whom were diagnosed with MG and 31 of whom were not diagnosed with MG.[1] Compared to non-MG patients, MG patients were younger, tended to have less advanced tumors according to the TNM classification and demonstrated a prognostic protective role in terms of lower recurrence and longer survival.[1] The work is compelling, but some points should be discussed.

For the MG group, it would be interesting to know how many years after the onset of MG, on average, a thymoma was discovered. Delayed detection of thymoma would be surprising because when MG is detected, MG patients should routinely undergo computed tomography (CT) of the mediastinum to determine whether MG is related to a thymoma or not. How many patients were diagnosed with MG before thymoma and vice versa?

A second point is that the imaging method used to detect the thymoma has not been reported. We should know whether mediastinal CT, chest magnetic resonance imaging, or scintigraphy was performed to detect the thymoma. In how many patients was a thymoma discovered by change and in how many through an active, prospective search for the tumor?

A third point to discuss is that the type of myasthenia diagnosed in the 39 patients was not specified. Were all 39 patients actually suffering from MG or were there also patients with ocular myasthenia? There is also no mention whether the myasthenia was due to antibodies to postsynaptic acetylcholine receptors, to antibodies against MUSK, or to an unknown pathophysiology.

A fourth point is the retrospective design of the study. Retrospective designs have several disadvantages. A retrospective design does not allow the control of the accuracy of the data stored, does not systematically apply the same examinations to all included patients, produces missing data, does not allow the addition of missing data, and is not suitable for generating desirable new data. Retrospective concepts also carry the disadvantage that the diagnostic and therapeutic methods may have changed over time.

A fifth point is that the treatment of myasthenia was not included in the analysis and discussion. Since the treatment of myasthenia can greatly influence the course and outcome of the disease, it is imperative to know what type of treatment each patient was regularly receiving at the time of surgery. Since most MG patients require immunosuppression and immunosuppression can be complicated by infection and, therefore, complicate the postoperative course, it is important to be informed about the therapeutic management of the 39 patients.

A sixth point is that there was no discussion as to why some patients with thymoma developed MG while other patients did not. Is this due to genetic factors, the type of thymoma, or due to the host’s immunologic response to the thymoma?

In summary, the study has limitations, which complicate the interpretation of the results. Addressing these limitations could strengthen and reinforce the statement of the study. In order to assess the differences between thymoma patients with and without MG, it is necessary to include all information about MG patient in the analysis.

Author contribution

JF was responsible for the design and conception, discussed available data with coauthors, wrote the first draft, and gave final approval. SM: Contributed to literature search, discussion, correction, and final approval.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.