Park Sujin, Kim Hyun-Soo
Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 06351, Korea.
Diagnostics (Basel). 2020 Aug 11;10(8):580. doi: 10.3390/diagnostics10080580.
Mucinous carcinoma of the retroperitoneal origin is extremely rare. The existence of mural nodules in association with retroperitoneal mucinous carcinoma is an even rarer condition and indicates a worse prognosis. We present a case of primary retroperitoneal mucinous carcinoma with carcinosarcomatous mural nodules in a 27-year-old woman. We found a histological spectrum of mucinous tumors encompassing a mucinous borderline tumor, microinvasive carcinoma, and overt carcinoma with an expansile invasive pattern. The mural nodules had two morphological components. The sarcomatous component consisted of diffusely proliferating pleomorphic spindle or polygonal cells, while the carcinomatous component exhibited infiltrative glands showing a complex and cribriform architecture as well as distorted and poorly formed small glands. The carcinomatous component, comprising approximately 20% of the entire tumor volume of the mural nodules, was randomly distributed within the sarcomatous component. In a few areas, the carcinomatous component transformed and merged into the sarcomatous component. Immunostaining revealed a mutually exclusive pattern of expression of cytokeratin and vimentin in the carcinomatous and sarcomatous components, respectively, supporting the presence of a dual tumor cell population and confirming the diagnosis of carcinosarcoma. In summary, our case exhibited a histological spectrum of mucinous tumors and a metaplastic transformation from the carcinomatous to sarcomatous component in mural nodules. The immunostaining results of a mutually exclusive expression pattern of epithelial and mesenchymal markers confirmed the histological evidence of a dual population. Although rare, the specific histological features and immunophenotype are helpful in establishing the diagnosis of carcinosarcomatous mural nodules. Since the pathogenetic mechanism and treatment strategies for primary retroperitoneal mucinous carcinoma remain unclear, pathologists have an essential role to play in correctly evaluating the presence of mural nodules and determining their nature, to be later utilized to predict patients' outcomes and provide appropriate treatment.
腹膜后起源的黏液性癌极为罕见。伴有壁结节的腹膜后黏液性癌更是罕见，且提示预后较差。我们报告一例27岁女性原发性腹膜后黏液性癌伴癌肉瘤性壁结节的病例。我们发现黏液性肿瘤的组织学谱系包括黏液性交界性肿瘤、微浸润癌和具有膨胀性浸润模式的明显癌。壁结节有两种形态成分。肉瘤成分由弥漫性增生的多形性梭形或多边形细胞组成，而癌成分表现为浸润性腺体，呈复杂的筛状结构以及扭曲和形态不佳的小腺体。癌成分约占壁结节整个肿瘤体积的20%，随机分布于肉瘤成分内。在少数区域，癌成分转变并融合到肉瘤成分中。免疫组化显示细胞角蛋白和波形蛋白分别在癌成分和肉瘤成分中呈相互排斥的表达模式，支持双肿瘤细胞群的存在并确诊为癌肉瘤。总之，我们的病例展示了黏液性肿瘤的组织学谱系以及壁结节中癌成分向肉瘤成分的化生转变。上皮和间充质标志物相互排斥表达模式的免疫组化结果证实了双细胞群的组织学证据。尽管罕见，但特定的组织学特征和免疫表型有助于确立癌肉瘤性壁结节的诊断。由于原发性腹膜后黏液性癌的发病机制和治疗策略仍不清楚，病理学家在正确评估壁结节的存在并确定其性质方面起着至关重要的作用，以便随后用于预测患者的预后并提供适当的治疗。
