Jain Pragya Virendrakumar, Thompson Jonathan, Sheinin Yuri
Department of Pathology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
Division of Hematology and Oncology, Department of Medicine, Medical College of Wisconsin Cancer Center, Milwaukee, Wisconsin, USA.
BMJ Case Rep. 2023 Apr 3;16(4):e253918. doi: 10.1136/bcr-2022-253918.
Small cell lung carcinoma (SCLC), a malignancy of neuroendocrine origin, can show varied morphologies and patterns but is typically positive for at least one neuroendocrine marker and almost always for cytokeratins. It is essential to distinguish this tumour due to its characteristic genetic features, aggressive behaviour, propensity for metastasis and responsiveness to chemotherapy. We hereby present a rare case of a pulmonary mass that showed morphological features of an SCLC but lacked cytokeratin expression on biopsy as well as resection specimens. Various cytokeratins were tested on multiple blocks and at different laboratories. A broad differential diagnosis was considered and ruled out including small round blue cell tumours, non-SCLC and metastasis. After performing an extensive work-up to identify the origin of this tumour, it was finally diagnosed as SCLC with expression of neuroendocrine markers synaptophysin and CD56, and intracytoplasmic electron dense neurosecretory granules (250-350 nm) however lacked cytokeratin expression.
小细胞肺癌（SCLC）是一种神经内分泌起源的恶性肿瘤，可表现出多种形态和模式，但通常至少对一种神经内分泌标志物呈阳性，几乎总是对角蛋白呈阳性。由于其独特的遗传特征、侵袭性、转移倾向和对化疗的反应性，区分这种肿瘤至关重要。我们在此报告一例罕见的肺部肿块病例，该肿块在活检及切除标本上显示出SCLC的形态特征，但缺乏细胞角蛋白表达。在多个组织块和不同实验室对多种细胞角蛋白进行了检测。考虑并排除了包括小圆细胞肿瘤、非小细胞肺癌和转移瘤在内的广泛鉴别诊断。在进行了广泛的检查以确定该肿瘤的起源后，最终诊断为SCLC，其表达神经内分泌标志物突触素和CD56，并且存在胞质内电子致密神经分泌颗粒（250 - 350nm），然而缺乏细胞角蛋白表达。
