Thank you Mia for presenting a case yesterday of a middle-aged previously healthy man who presented with an acute onset, pleuritic chest pain and was found to have a R sided, pleural-based, ectopic thymoma (picture below). See below for pearls on thymoma, and check out the clinical image that was published on this patient: http://www.sgim.org/web-only/clinical-images/in-the-chest-but-not-of-the-chest
- There are no known risk factors for development of a thymoma, but there is a strong association with Myasthenia Gravis and other paraneoplastic syndromes (The estimated incidence of thymoma in patients with Myasthenia Gravis is ~21%).
- In all patients diagnosed with Myasthenia Gravis (MG), imaging is warranted to look for an underlying thymoma
- Although MG frequently improves with resection of a thymoma, other paraneoplastic disorders (pure red cell aplasia, hypogammaglobulinemia) associated with thymomas often do not improve despite surgical resection.
- Remember, that the thymus is an anterior mediastinal organ that reaches its maximum weight around puberty, and then involutes and persists in an atrophic state into old age. Thymus is primarily involved in the maturation of T-lymphocytes.
- Thymomas account for 20% of mediastinal neoplasms!
- Several paraneoplastic disorders are associated with thymoma:
- Myasthenia Gravis : common in all types of thymoma but rare in thymic carcinoma : A recent systematic review search showed that the incidence of thymoma in MG was 21%. (Mao et al., Journal of Clinical Neurology; PMID 23091524) : In patients with thymoma and MG, thymectomy usually results in attenuation of severity of MG. As such, when an adult patient is diagnosed with MG, an imaging is warranted to look for an underlying thymoma!
- Pure red cell aplasia
: due to auto-immune mediated hypoproliferation of erythrocyte precursors. : remission of aplasia after surgical excision alone is uncommon.
- Hypogammaglobulinemia: present in < 5% of patients with thymoma
- Thymoma-associated multiorgan autoimmunity (TAMA): rare case reports of a condition that is akin to GVHD (skin eruptions, diarrhea, liver enzyme abnormalities).
- Treatment is aimed towards complete resection. If complete resection is not feasible, neoadjuvant chemotherapy or chemoradiotherapy may be used prior to surgical resection.