Wan S K, Chan J K, Tang S K
Department of Pathology, Queen Elizabeth Hospital, Kowloon, Hong Kong.
Am J Clin Pathol. 1996 Apr;105(4):388-93. doi: 10.1093/ajcp/105.4.388.
Anaplastic thyroid carcinomas usually pose no problems in histologic diagnosis because of the obvious invasive growth, high cellularity, and frank anaplasia. Two cases of a variant of anaplastic thyroid carcinoma with peculiar gross and histologic features closely mimicking those of Riedel's thyroiditis are described in this report. The clinical features were no different from those of the usual anaplastic thyroid carcinomas: occurrence in elderly subjects, presentation with rapidly enlarging neck mass associated with compression symptoms, and rapidly fatal outcome. The tumors were infiltrative, hard, fibrotic masses that partly or completely replaced one lobe of the thyroid, and extended to perithyroid tissues. Histologically, they were predominated by acellular fibrous or infarcted tissue with central dystrophic calcification, as well as hypocellular foci comprising mildly atypical spindle cells intermingled with collagen and small lymphocytes. Both cases showed permeation and plugging of the arteries by tumor. Lymph node metastasis was documented in one case. The spindle cells were positive for epithelial membrane antigen in both cases, and cytokeratin in one. The qualifying term "paucicellular variant" accurately describes this uncommon morphologic variant of anaplastic thyroid carcinoma. It is important to recognize this variant so as not to mistaken it for Riedel's thyroiditis, which is a reactive condition with a very favorable prognosis. The distinguishing features are as follows: presence of infarction, atypical cells in at least some areas, atypical spindle cells obliterating large blood vessels, and immunoreactivity for epithelial markers.
间变性甲状腺癌通常在组织学诊断上不存在问题，因为其具有明显的浸润性生长、高细胞密度和明显的间变特征。本报告描述了两例间变性甲状腺癌变体病例，其具有独特的大体和组织学特征，与Riedel甲状腺炎极为相似。临床特征与常见的间变性甲状腺癌无异：发生于老年患者，表现为颈部肿块迅速增大并伴有压迫症状，且预后迅速恶化。肿瘤为浸润性、坚硬、纤维化肿块，部分或完全取代甲状腺的一叶，并延伸至甲状腺周围组织。组织学上，肿瘤主要由无细胞纤维组织或梗死组织构成，伴有中央营养不良性钙化，以及由轻度非典型梭形细胞与胶原和小淋巴细胞混合组成的低细胞灶。两例均显示肿瘤对动脉的浸润和阻塞。其中一例记录有淋巴结转移。两例中的梭形细胞上皮膜抗原均呈阳性，一例细胞角蛋白呈阳性。限定词“少细胞变体”准确地描述了这种间变性甲状腺癌罕见的形态学变体。认识到这种变体很重要，以免将其误诊为Riedel甲状腺炎，后者是一种反应性疾病，预后非常好。其鉴别特征如下：存在梗死、至少某些区域有非典型细胞、非典型梭形细胞阻塞大血管以及上皮标记物免疫反应阳性。
