Department of Pathology, McGill University, Montreal, Quebec, Canada.
Diagn Cytopathol. 2020 Jul;48(7):679-683. doi: 10.1002/dc.24431. Epub 2020 Apr 9.
High-grade transformation (HGT) or "dedifferentiation" is an uncommon phenomenon among salivary gland carcinomas including adenoid cystic carcinoma (ACC), which is important to recognize because it is associated with increased tumor aggressiveness, with a high propensity for lymph node and distant metastases. ACC with HGT is histologically characterized by a distinct population of poorly differentiated cells with loss of the typical biphasic ductal and myoepithelial differentiation seen in conventional ACC, associated with pleomorphism, necrosis and increased mitotic activity. We report the cytologic features of a case of metastatic ACC-HGT in cervical lymph node and effusion, which, to the best of our knowledge, have not been described previously. When ACC presents both in atypical locations and with HGT, the danger of misdiagnosis is increased if the clinical history is lacking, incomplete or inaccurate. Since ACC-HGT are rare (and possibly underdiagnosed) and do not have a specific set of cytological and/or immunohistochemical features, it is important for practicing cytopathologists to be aware of the possibility of encountering them, especially in specimens from patients with a history of ACC, in order to render the correct diagnosis.
高级别转化（HGT）或“去分化”在包括腺样囊性癌（ACC）在内的唾液腺癌中较为罕见，这一点很重要，因为它与肿瘤侵袭性增加有关，淋巴结和远处转移的倾向也较高。具有 HGT 的 ACC 在组织学上的特征是存在明显的分化不良细胞群，缺乏在常规 ACC 中见到的典型双相导管和肌上皮分化，伴有多形性、坏死和增加的有丝分裂活性。我们报告了一例转移性 ACC-HGT 在颈部淋巴结和渗液中的细胞学特征，据我们所知，以前尚未对此进行描述。当 ACC 出现在非典型部位且具有 HGT 时，如果临床病史缺失、不完整或不准确，则误诊的风险会增加。由于 ACC-HGT 较为罕见（且可能诊断不足），并且没有特定的细胞学和/或免疫组织化学特征集，因此对于临床细胞学医生来说，了解遇到它们的可能性很重要，尤其是在来自有 ACC 病史的患者的标本中，以便做出正确的诊断。
