Thymoma exhibiting spontaneous regression with developing myasthenia gravis: A case report

Area of Science:

• Oncology
• Neurology
• Pathology

Background:

• Spontaneous regression (SR) of thymoma is an exceedingly rare phenomenon.
• Thymomas are anterior mediastinal tumors often associated with myasthenia gravis (MG).

Observation:

• A 44-year-old man presented with an 11 cm anterior mediastinal mass and pleural effusion.
• The mass spontaneously regressed by over 50% within one year without treatment.
• Four years later, the patient developed diplopia and fatigue, diagnosed as myasthenia gravis.

Findings:

• Histologic analysis confirmed thymoma type B2, Masaoka stage IIa, with SR attributed to intratumoral infarction.
• This is the first reported case of myasthenia gravis developing during the spontaneous regression of a thymoma.
• The regressed mediastinal mass measured 3.0 cm at the time of MG diagnosis and subsequent thymectomy.

Implications:

• Anterior mediastinal tumors undergoing spontaneous regression require careful differentiation from thymomas.
• The potential for perioperative development of myasthenia gravis in patients with regressing thymomas should be considered.
• This case underscores the complex interplay between thymoma, spontaneous regression, and autoimmune manifestations like myasthenia gravis.