Development of combined thymic carcinoma and thymoma in an extrathymic lesion during long follow-up for recurrent thymoma

Abstract

Abstract. The present study reported a rare case of combined thymic squamous cell carcinoma and thymoma exhibiting a mass on the left chest wall. The patient underwent thoracotomy for invasive thymoma 15 years previously, however, suffered a relapse in the left intrathoracic space. Radiotherapy, chemotherapy and partial resection, as secondary surgery for the intrathoracic mass, were performed. The histological findings in the resected specimens revealed type B3 thymoma. As the patient developed a left chest wall mass and pain in 2013, the mass was resected. The histological findings indicated two separate components composed of type B3 thymoma and squamous cell carcinoma. Immunohistological findings revealed that the thymoma cells were positive for CD5, while the thymic carcinoma cells were negative for CD5. Several reports have demonstrated the coexistence of thymic carcinoma and thymoma in the primary thymus, however, the development of a combined tumor in an extrathymic lesion is extremely rare. The present case had a long follow-up for recurrent thymoma. The present case indicated that the development and/or coexistence of malignant components in the thymoma must be taken into consideration for the treatment and/or management of patients with thymoma and that a pre-existence of CD5 expression in thymoma and the lost change may be associated with the process of malignant transformation.

Review of the literature about Thymic Carcinomas

“…These studies reported that the vascular invasion was a bad prognosis factor and that it needs to be integrated in the staging system [46,57,71]. The surgical resecability of thymic carcinomas has been reported in many studies [4][5][6]8 [22]. The extension of the surgical resection has also been considered as a prognostic factor especially when associated to a lymph node curettage [8,23].…”

“…After a complete surgical resection, the utility of radiation therapy has been debated in the literature and was reported to have no effect on the global survival or the survival without progression [5,22,56,58]. For low grade tumors, some authors reported the role of radiation therapy following surgical resection in the decrease of loco regional recurrences and secondary localizations [6,9,28,36,54,61,62,66,80,92].…”

“…The expression of Kit was also used as a diagnostic tool of these tumors [39,93] [8,31,67]. Nine studies reported that the staging wasn't a relevant prognostic factor [6,9,19,20,30,46,57,71,74]. These studies reported that the vascular invasion was a bad prognosis factor and that it needs to be integrated in the staging system [46,57,71].…”

“…Adjuvant chemotherapy or radiation therapy have been also reported as a good prognostic factor related to the global survival and the survival without progression. [6,9,28,36,54,61,62,66,80].…”

“…Clinical symptoms are nonspecifi c resulting in a delayed diagnosis [1,[3][4][5][6][7][8][9][10]. Radiological fi ndings are also nonspecifi c. In fact, they help to highlight the malignant nature of the tumor without presuming of its nature.…”