Thymoma is the most common anterior mediastinal tumor, but it is a rare malignancy overall, with an incidence of approximately 0.13 cases per 100,000 individuals annually (1). Thymomas are often associated with a variety of immune abnormalities, particularly autoimmune diseases such as myasthenia gravis and pure red cell aplasia (PRCA). PRCA is a rare hematological disorder characterized by significant normocytic, normochromic anemia, reduced reticulocytes, and selective marked reduction of erythroid precursors in the bone marrow.

Cases of thymoma complicated by PRCA are typically treated by tumor resection plus immunosuppressive therapies such as cyclosporine, steroids and cyclophosphamide (2,3). However, the effectiveness of these treatments varies greatly among individuals, and no standardized treatment guidelines have been established. Meanwhile, systemic chemotherapy becomes the mainstay of treatment in cases of metastatic or inoperable advanced thymoma wherein surgical resection is not an option. In such situations, using immunosuppressive therapy requires great caution due to the risk of additive toxicity when combined with cytotoxic agents and the potential for serious infectious complications. In cases where immunosuppressive agents cannot be administered, long-term transfusion support is often required for the management of PRCA-associated anemia.

This case report describes a patient with metastatic thymoma complicated by PRCA. The initial treatment was cytotoxic chemotherapy with the ADOC regimen, which achieved tumor control and prolonged transfusion intervals. This therapeutic response enabled the subsequent initiation of immunosuppressive therapy and thymectomy, ultimately leading to successful withdrawal from transfusion dependence. This extremely rare clinical course suggests the potential of cytotoxic chemotherapy (in addition to immunosuppressive therapy) as a therapeutic option for thymoma-associated PRCA. This case provides valuable insight that contributes to the accumulation of clinical experience and aids in the future development of evidence-based treatment guidelines.

PRCA reportedly occurs in approximately 5% of patients with thymoma (4,5). The standard management includes surgical resection of the thymoma plus immunosuppressive therapy, among which cyclosporine is the most frequently reported effective agent (2,3).

In the present case, multiple bilateral pulmonary metastases were identified at the initial visit, and therefore systemic chemotherapy was prioritized over local treatment. The ADOC regimen was chosen due to its previously demonstrated efficacy in invasive thymoma (6). Initially, the patient required weekly transfusions of 2 units of red blood cells, and this progressively intensified until daily transfusions of 2 units were needed to maintain a hemoglobin level of 7 g/dl at the initiation of chemotherapy. Remarkably, after only a single cycle of ADOC, the transfusion requirement decreased to 2 units every 7–17 days.

In patients with metastatic thymoma complicated by PRCA, immunosuppressive therapy (e.g., cyclosporine) may delay the initiation of systemic chemotherapy. The concomitant administration of immunosuppressive agents and cytotoxic chemotherapy may also increase treatment-related toxicity. Meanwhile, the present case demonstrates that transfusion dependence due to PRCA can be ameliorated with cytotoxic chemotherapy alone. Such reports are exceedingly rare, and only isolated cases have been previously documented (7). This case provides valuable insight into a potential therapeutic strategy in similarly complex clinical scenarios. The decreased transfusion dependence seen after the ADOC regimen could be because the hematological improvement occurred concurrently with radiographic tumor shrinkage. In other words, the antitumor effect of chemotherapy may have helped ameliorate PRCA as a paraneoplastic syndrome. The reduced tumor burden could have attenuated the immune dysregulation caused by the thymoma, thereby partially restoring erythropoiesis. Although components of the ADOC regimen, particularly cyclophosphamide and the corticosteroids administered as part of antiemetic prophylaxis, may have contributed to the hematological improvement through their immunosuppressive effects, the regimen was primarily administered for its antitumor activity. Reports describing improvement of PRCA in this context remain extremely limited; therefore, this case may provide clinically meaningful insight into situations in which determining the optimal sequencing of chemotherapy and immunosuppressive therapy is challenging. Nevertheless, due to the inherent limitations of being a single case report, definitive conclusions regarding the underlying mechanism cannot be drawn. Although the transfusion-dependent anemia improved alongside the antitumor response in this patient, previous reports have suggested that antitumor effects do not necessarily correlate with the therapeutic effect on PRCA as a paraneoplastic syndrome (8). Thus, treatment strategies should be individualized according to the clinical course in each case, and further accumulation of similar cases is warranted.

After six cycles of ADOC, the primary thymic tumor was markedly reduced, and the pulmonary metastases also demonstrated significant shrinkage with partial obscuration. No new metastatic lesions were detected at that time. Although transfusion dependence had improved compared with the pre-chemotherapy status, the patient still required red blood cell transfusions every 7–17 days. Based on these findings, a multidisciplinary discussion was conducted, and surgical resection of the primary thymic tumor was planned. In this context, it is important to note that the pulmonary metastatic lesions had already shown marked shrinkage following systemic chemotherapy. Furthermore, a previous meta-analysis has suggested a potential survival benefit of debulking surgery in patients with unresectable thymoma (9). Taking these factors into account, a multidisciplinary team-including thoracic surgeons, oncologists, and hematologists-concluded that surgical resection at a time when the primary tumor had sufficiently regressed would be a reasonable strategy. After completing six cycles of chemotherapy in preparation for surgery, it became feasible to initiate immunosuppressive therapy. Cyclosporine was started in December 2025, and surgical resection of the primary thymoma was performed in January 2026. Two weeks after initiating cyclosporine, the patient received two units of red blood cells, which was the final transfusion required. Thereafter, the patient achieved transfusion independence and has remained free from further transfusion support. For future management, cyclosporine will be continued, and the patient will undergo regular imaging follow-up. If pulmonary lesions become clinically apparent, local treatment with radiofrequency ablation will be considered.

Several case reports have described tumor shrinkage of thymoma accompanied by improvement of PRCA after cyclosporine therapy (8,10). Despite the limited evidence, the potential antitumor effect of cyclosporine cannot be excluded. Nevertheless, in patients with metastatic thymoma complicated by PRCA, further investigation is required to clarify whether systemic chemotherapy should be prioritized or if early introduction of cyclosporine is preferable. The significance of this case lies in the fact that the ADOC regimen achieved both an antitumor effect and partial improvement of PRCA in metastatic thymoma, which subsequently enabled surgical resection and the initiation of cyclosporine therapy, ultimately leading to transfusion independence. The present evidence suggests that treatment decisions should be individualized alongside careful evaluation of both oncological and hematological responses. Further accumulation of clinical evidence regarding this rare and therapeutically challenging condition is essential to develop optimal therapeutic strategies.