Department of Diagnostic Pathology, Faculty of Medicine, Oita University, Yufu, Japan.
Int J Surg Pathol. 2023 Aug;31(5):785-790. doi: 10.1177/10668969221133357. Epub 2022 Oct 30.
Micronodular thymic carcinoma (MTC) with lymphoid hyperplasia is believed to be the malignant counterpart of micronodular thymoma (MT) with lymphoid hyperplasia. Since MT and MTC share a similar morphology, MTC is considered a malignant form of MT; there have been a few malignant transformations from MT to MTC. We report a case of MTC with lymphoid hyperplasia. A 53-year-old woman presented with an incidental tumor on a chest X-ray. The resected tumor consisted of nodular epithelial nests and lymphoid tissue within a surrounding germinal center. Some epithelial nests showed apparent malignant morphology. Atypical epithelial cells with large vesicular nuclei formed nests, some of which showed comedo necrosis. These cells showed transition continuously to low-grade type B thymoma-like cells, demonstrating cord-like arrangements. Carcinomatous elements, expressed GLUT1, CD5, KIT, and BCL2; conversely, low-grade nests displayed attenuated expression of these markers. point mutation and Langerhans/dendritic cells, which are indicators of favorable thymoma prognosis, were not detected. Due to pleural metastasis, the patient was treated with lenvatinib 27 months postoperatively. This is the first report of a partially low-grade, -negative MTC. Histological and genetic findings might be predictive of tumor prognosis.
微结节性胸腺癌（MTC）伴淋巴组织增生被认为是微结节性胸腺瘤（MT）伴淋巴组织增生的恶性对应物。由于 MT 和 MTC 具有相似的形态学特征，因此 MTC 被认为是 MT 的恶性形式；已经有少数 MT 向 MTC 恶变的病例报道。我们报告一例伴淋巴组织增生的 MTC。一名 53 岁女性因胸片上偶然发现的肿瘤就诊。切除的肿瘤由结节状上皮巢和周围生发中心内的淋巴组织组成。一些上皮巢表现出明显的恶性形态。大泡状核的不典型上皮细胞形成巢，其中一些巢表现出粉刺样坏死。这些细胞连续向低级别 B 型胸腺瘤样细胞过渡，表现出索状排列。癌性成分表达 GLUT1、CD5、KIT 和 BCL2；相反，低级别巢表达这些标志物的强度减弱。未检测到点突变和朗格汉斯/树突状细胞，这些是胸腺瘤预后良好的指标。由于存在胸膜转移，患者在术后 27 个月接受仑伐替尼治疗。这是首例部分低度、CD5 阴性 MTC 的报告。组织学和遗传学发现可能对肿瘤预后具有预测价值。
