岡部 直太

Mediastinal tumors have many differential diagnoses, making it challenging to confirm a diagnosis through imaging alone. We report a case of mediastinal recurrence of breast cancer mimicking a thymic tumor, with invasion of the left innominate vein, occurring 13 years post surgery. Given the tumor thrombus extending into the superior vena cava (SVC), surgical resection was performed to prevent life-threatening complications and to achieve definitive diagnosis and treatment. Breast cancer is known for its slow growth and late recurrence. While axillary lymph nodes (ALNs) are the most common site of breast cancer drainage, alternative pathways such as the internal mammary lymph nodes may also play a role in disease spread. Recurrence of breast cancer in IMLN can mimic mediastinal tumors, such as thymoma or thymic cancer. Therefore, in patients with a history of breast cancer, a mediastinal tumor should raise suspicion for breast cancer recurrence, even if it involves the innominate vein or occurs after a long interval.

Immunoglobulin G4-related disease (IgG4-RD) is a recently identified systemic fibroinflammatory disorder affecting various organs throughout the body. IgG4-related lung disease is a relatively common manifestation in IgG4-RD and presents with 4 primary pulmonary patterns: nodular, ground-glass opacities, interstitial disease, and peribronchovascular thickening. Peribronchovascular thickening is a frequent pattern in thoracic IgG4-RD involvements. This case report describes bronchial obstruction as a consequence of IgG4-RD in a 65-year-old man with no personal or family history of autoimmune disease. Thoracoscopic segmentectomy was performed, which led to the diagnosis of IgG4-RD.

A 76-year-old woman with persistent diarrhea was referred to our hospital. She had purpura, peripheral eosinophilia (18,177/μL), and an elevated serum IgG4 level (819 mg/dL). Abdominal computed tomography revealed massive ascites and bowel edema. A skin biopsy of the purpura revealed leukocytoclastic vasculitis with prominent eosinophilic infiltration. Biopsies of the gastrointestinal mucosa revealed dense eosinophilic infiltration, indicating eosinophilic gastroenteritis (EG) associated with the hypereosinophilic syndrome. The number of IgG4-positive cells increased in the duodenal mucosa; however, the diagnostic criteria for IgG4-related disease (IgG4-RD) were not met. Whether or not EG with ascites is a manifestation of IgG4-RD warrants further investigation.

Ovarian mesonephric-like adenocarcinoma is rare and poorly understood, and preoperative diagnosis of this tumor with any diagnostic modality is challenging. Histological features can only be speculated through imaging. Herein, we present the case of a 64-year-old woman with primary ovarian mesonephric-like adenocarcinoma, characterized by a 13 cm pelvic mass detected via ultrasound. Further evaluation with magnetic resonance imaging showed low signal intensity in the solid component on T2-weighted images and high signal intensity on diffusion-weighted images, along with a smooth margin; these findings are consistent with those of previous reports. The patient underwent a total abdominal hysterectomy, bilateral salpingo-oophorectomy, and partial omentectomy. Postoperative pathology confirmed mesonephric-like adenocarcinoma with positive peritoneal cytology. Immunohistochemical analysis showed a positive result for GATA-3 and a negative result for thyroid transcription factor-1. The patient was diagnosed with stage IC3 mesonephric-like adenocarcinoma, and adjuvant chemotherapy with paclitaxel and carboplatin was initiated. Mesonephric-like adenocarcinoma can present with distinct imaging features, including low signal intensity on T2-weighted imaging and high signal intensity on diffusion-weighted imaging, with a smooth solid margin; these imaging features may aid in the preoperative differentiation from other ovarian malignancies, such as serous or clear cell carcinomas.

Various studies have reported resistance mechanisms and treatment methods after epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor treatment; however, treatment policies have not yet been established, and few cases have reported transformation to pleomorphic carcinoma (PC) as the resistance mechanism. Herein, we report the case of a 66-year-old woman who was diagnosed with Stage 4A lung adenocarcinoma (cT2bN0M1b) through bronchoscopic biopsy. Genetic profiling revealed an EGFR L858R mutation; therefore, osimertinib was administered as the first-line therapy and achieved a partial response. After 46 months of osimertinib treatment, the metastases remained under control; however, the primary tumor enlarged and was therefore resected. Pathological examination confirmed the diagnosis of PC. Genetic testing of the surgical pathology specimen showed that the EGFR mutation L858R was retained, and the patient was considered drug-resistant owing to the histologic transformation to PC. The patient continued osimertinib therapy and had no recurrence at 9 months postoperatively. Transformation to PC following osimertinib administration is rare, and we report this unique case. This study was approved by the Jichi Medical University Saitama Medical Center Ethics Committee (S24-073), and written informed consent was obtained from the patient.