Thymoma with Extensive Necrosis: A Case Report and Literature Review

Abstract

Introduction: Thymomas are associated with necrosis and hemorrhage in approximately 5% of cases; however, cases in which necrotic tissue constitutes the majority of tumors are rare.

Case presentation: A 30-year-old man was referred to our hospital with transient anterior chest pain and a mediastinal mass detected on a health check-up. Positron emission tomography/computed tomography showed no fluorodeoxyglucose uptake, and serum and biochemical analyses revealed no elevated inflammatory responses or tumor marker levels. Based on imaging findings, thymic cysts and thymomas were considered differential diagnoses, and thoracoscopic mediastinal tumor resection was performed. The encapsulated tumor, which was adherent to the lung via the thickened pleura, was successfully resected, and a rapid diagnosis of thymoma was made. Final pathological examination confirmed a type B2 thymoma, with necrosis comprising approximately 80% of the tumor. The patient has been followed up on an outpatient basis, with no recurrence at 1 year after surgery.

Conclusions: Extensive necrosis in thymic tumors often suggests high-grade malignancy, but may also occur in necrotic thymoma with a favorable prognosis. Recognizing this possibility is essential to avoid overtreatment and guide appropriate surgical management.

Keywords: mediastinal tumor; necrosis; thymoma.

Fig. 1. Preoperative image. Chest computed tomography shows a 35 × 25 mm mass on the left side of the anterior mediastinum in the lung (A: arrow) and mediastinal windows (B: arrow). Positron emission tomography with 18-F-fluorodeoxyglucose demonstrated no accumulation in the mass (C: arrow).

Fig. 2. Intraoperative image. Thoracoscopy revealed a 30-mm-sized mass in the anterior mediastinum (arrow) with mild fibrous adhesions to the lung (A). The mass was resected along with as much surrounding thymic tissue as possible (B).

Fig. 3. Pathological findings (the cut surface). The cut surface of the surgical specimen measured 50 mm in diameter and 30 mm in width, exhibiting a uniform yellowish-white coloration. The tumor area is demarcated by a white dashed line. The areas outside the dashed lines represent thymic tissue.

Fig. 4. Pathological findings (macroscopic image). Macroscopic finding (loupe image) of the largest segment of the resected tumor. The tumor capsule is outlined by a dashed line, and a dotted line marks the basophilic region, which is visually distinguishable. Viable thymic epithelial cells were identified within the basophilic region.

Fig. 5. Pathological findings (microscopic image). The magnified image illustrates the boundary between the acidophilic and basophilic regions in Fig. 3 (A). In the HE-stained acidophilic region, thymic epithelial cells exhibited signs of coagulation necrosis, characterized by cytoplasmic acidification and nuclear enrichment and loss (B). HE staining also revealed basophilic regions containing poorly atypical thymic epithelial cells, along with aggregates of lymphocytes and a reticulated arrangement. Within the basophilic region, necrotic changes were noted in a worm-eaten pattern, with residual thymic tissue appearing as islands (C). Immunohistochemical analysis demonstrated the presence of CD3-positive T cells and reticulated thymic epithelial cells in the residual thymic tissue (D).

HE, hematoxylin and eosin