Analysis of outcomes following surgical treatment of thymolipomatous myasthenia gravis: comparison with thymomatous and non-thymomatous myasthenia gravis

Abstract

Objectives: Although significant improvement in myasthenic symptoms has been reported following the removal of thymolipomas, information on surgical outcomes among patients with thymolipomatous myasthenia gravis (MG) is limited.

Methods: This was a retrospective review of patients who underwent extended thymectomy for treatment of MG.

Results: From 1995 to 2010, 267 patients with MG underwent extended thymectomy, including 104 with thymomatous MG, 151 with non-thymomatous MG and 12 (4.4%) with thymolipoma. The mean duration of myasthenic symptoms before surgery was greatest in the thymolipomatous group (P < 0.001). The lowest mean age (36.1 years old, P < 0.001) and the lowest preoperative serum anti-acetylcholine receptor antibody titre (P = 0.015) occurred in the non-thymomatous group. More thymic and adipose tissue was removed from the thymolipomatous group compared with the non-thymomatous group (P < 0.001). Regarding surgical outcomes, the rate of stable remission was higher in the non-thymomatous (42.3%) and thymolipomatous (41.7%) groups compared with the thymomatous group (28.8%, P = 0.029). No instances of postoperative exacerbation of MG or tumour recurrence were noted during the postoperative follow-up of patients treated for thymolipoma.

Conclusions: Our results suggest that patients with myasthenia thymolipomatous have surgical outcomes similar to those of patients with non-thymomatous MG and have a mean age at the time of surgery similar to that of patients with thymomatous MG.

Keywords: Anterior mediastinal tumour; Myasthenia gravis; Thymectomy; Thymolipoma.

Figure 1:

Histopathology of thymolipoma. (A) The thymolipoma contains of abundant mature adipose tissue scattered with remnants of thymic tissue. The fat cells show no cytological atypia, and the thymic component is composed of strands and nests of atrophic thymic epithelium and lymphoid tissue; (B) Hassall's corpuscle in the thymic tissue (arrow); (C) posteroanterior chest radiography in a 58-year old man shows mild widening of mediastinum; (D) contrast-enhanced chest CT shows fat attenuation and a suspected nodular lesion at the prevascular area of anterior mediastinum.

Figure 2:

Algorithm of the myasthenic patient selection.

Figure 3:

Kaplan–Meier cumulative estimate of the CSR rates following extended thymectomy in MG. There were no between-group differences in the probability of a CSR event at any time point during the follow-up period as determined by the log-rank test (P = 0.261). Non-thymomatous (filled triangle); thymomatous (inverted triangle); thymolipomatous (filled circle).