Peritoneal inclusion cysts (PICs) are unilocular or multilocular cystic lesions lined by bland mesothelial cells. While most are small and localized, rare examples may be large or multifocal with diffuse peritoneal involvement, causing clinical and even pathologic concern for malignancy. We examined 20 PIC, including 8 large solitary and 12 multifocal lesions. Solitary PIC were found in 7 female and 1 male patients ranging from 19 to 55 (median: 37) years. Expanded collagenous (n=2) or edematous (n=1) areas were occasionally seen in the septae, and 1 had microscopic foci of myxoid stroma. Four had hobnail cells, and 1 had minor areas of papillary mesothelial hyperplasia. Multifocal PICs occurred in 9 female and 3 male patients ranging from 26 to 80 (median: 53) years. Three showed extensive associated fibrosis with entrapment of preexisting adipose tissue, 2 had areas resembling granulation tissue, and 3 had scattered foci of myxoid stroma. Hobnail cells were present in 9, papillary mesothelial hyperplasia in 2, entrapped single cells in 1, and 2 had areas resembling adenomatoid tumors. Two of the multifocal PICs had limited local recurrences at 18 and 21 months. No patients died of disease. Clonal alterations were not identified in any of the tested PICs (mutational and fusion analysis in 5, chromosomal microarray in 1). Despite limited local recurrences, we demonstrate that even large and multifocal PICs may lack identifiable genomic alterations and are associated with benign outcomes.

中文翻译：

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尽管很少复发，但大而广泛的多房性腹膜包涵囊肿缺乏基因组改变，并且遵循惰性临床过程。


腹膜包涵体囊肿 (PIC) 是单房或多房囊性病变，内衬平淡的间皮细胞。虽然大多数是小且局部的，但罕见的例子可能是大的或多灶性的，伴有弥漫性腹膜受累，引起临床甚至病理学上的恶性肿瘤担忧。我们检查了 20 个 PIC，包括 8 个大的孤立病变和 12 个多灶性病变。 7 名女性和 1 名男性患者中发现孤立性 PIC，年龄范围为 19 至 55 岁（中位数：37）。间隔中偶尔可见扩张的胶原区域（n=2）或水肿区域（n=1），其中 1 个区域有粘液样基质的微观病灶。 4 例有平头钉细胞，1 例有小面积乳头状间皮增生。多灶性 PIC 发生在 9 名女性和 3 名男性患者中，年龄范围为 26 至 80 岁（中位数：53）。 3 个显示出广泛相关的纤维化，并伴有先前存在的脂肪组织的卡压，2 个具有类似肉芽组织的区域，3 个具有分散的粘液样基质病灶。 9 例存在鞋钉细胞，2 例存在乳头状间皮增生，1 例存在包埋单细胞，2 例具有类似腺瘤样肿瘤的区域。其中两例多灶性 PIC 在 18 个月和 21 个月时局部复发有限。没有患者因病死亡。在任何测试的 PIC 中均未发现克隆改变（5 中的突变和融合分析，1 中的染色体微阵列）。尽管局部复发有限，但我们证明，即使是大的多灶性 PIC 也可能缺乏可识别的基因组改变，并且与良性结果相关。