阑尾黏液性肿瘤的病理诊断及发生机制研究进展

阑尾黏液性肿瘤(appendiceal mucinous neoplasms, AMN)的认知近年逐渐深入,相关命名术语、诊断标准也进一步规范。阑尾低级别黏液性肿瘤(low grade appendiceal mucinous neoplasm, LAMN)应与一些组织学形态相似的病变相鉴别,避免过度诊断。其分期标准近年也有所变更,新近提出的阑尾高级别黏液性肿瘤(high grade appendiceal mucinous neoplasm, HAMN)命名被WHO(2019)消化系统肿瘤分类分册收录。AMN及锯齿状病变的分子机制研究亦取得一些新进展,该文着重对AMN的病理诊断和分子机制作一综述。     

阑尾黏液性肿瘤10例临床病理分析

目的：探讨阑尾黏液性肿瘤的临床病理学特征、诊断及预后。方法回顾性分析10例阑尾黏液性肿瘤的临床特点、组织病理学特征及随访结果。结果10例阑尾黏液性肿瘤中阑尾黏液性囊腺瘤(mucinous adnoma, MA)3例,黏膜上皮呈高柱状,分泌黏液,无明显异型性。阑尾低级别黏液性肿瘤( low grade apendiceal mucinous neoplasm, LAMN )5例,管壁可见无细胞或含少量细胞的黏液扩散至阑尾壁各层甚至阑尾外,其中1例伴有低级别腹膜假黏液瘤( low grade of peritoneal pseudomyxoma, PMP-L),腹膜病变组织学结构和细胞学特征与阑尾相同。阑尾黏液性囊腺癌( mucinous adnocarcinoma, MAC)2例,管壁可见腺管或筛状结构,细胞异型性较大,呈浸润性生长,1例伴有高级别腹膜假黏液瘤(high grade of peritoneal pseudomyxoma, PMP-H),腹膜黏液湖内可见多量异型性显著的黏液上皮细胞。结论阑尾黏液性肿瘤是一系列肿瘤谱系,其生物学行为取决于肿瘤性质和类型,准确且规范的病理诊断对治疗至关重要。     

以阑尾炎起病的阑尾上皮性肿瘤15例临床病理分析

目的:探讨以阑尾炎起病的阑尾上皮性肿瘤的临床病理学特征.方法:对15例以阑尾炎起病的阑尾上皮性肿瘤的临床病理资料进行回顾性分析.结果:15例以阑尾炎起病的阑尾上皮性肿瘤中,6例为低级别阑尾黏液性肿瘤(low-grade appendiceal mucinous neoplasm,LAMN),其余9例为前驱病变,包括8例锯齿状病变及1例绒毛状-管状腺瘤,其中锯齿状病变为6例无蒂锯齿状腺瘤/息肉(sessile serrated adenoma/polyp,SSA/P)及2例传统型锯齿状腺瘤(traditional serrated adenoma,TSA).14例以"急性阑尾炎"起病,1例以"慢性阑尾炎"起病.SSA/P镜下见锯齿状结构、隐窝扩张呈L或倒T形;TSA见显著的锯齿状轮廓和异位隐窝,具有细胞异型性;锯齿状病变的黏膜肌层完整.LAMN内衬轻度异性的黏液性上皮,管壁纤维化或破裂,管壁内及浆膜见无细胞性黏液池.9例获得随访包括5例前驱病变及4例LAMN,随访时间1.0~81.5个月,患者均无病生存.结论:阑尾锯齿状病变及LAMN均可因急性阑尾炎起病,锯齿状病变大多数为镜下偶然发现.外科医生应提高对这些病变的认识,以避免医源性穿孔导致的腹膜假黏液瘤.病理医生应将该类阑尾病变标本全部取材以便于鉴别诊断,报告阑尾切缘情况.     

女性腹膜假黏液瘤的组织学起源分析

目的探讨国人女性患者腹膜假黏液瘤的组织学起源。方法复习18例女性腹膜假黏液瘤患者的临床及病理资料，分别对每例患者腹膜、阑尾及卵巢的病变进行PV-6000法免疫组化标记，抗体有CK7、CK20、MUC-1、MUC-2、CA-125、ER及PR。结果18例腹腔内均见大量胶状黏液性肿瘤，17例患者有阑尾切除病史，其中黏液性病变15例，阑尾炎1例，1例外院手术病理不详；11例卵巢见黏液性肿瘤，7例为双侧，2例为右侧，2例为左侧；2例卵巢未见著变，5例术中未见病变，未予切除。18例中15例腹膜病变呈CK20及MUC-2阳性，而CK7、MUC-1、CA125、ER及PR阴性，阑尾与卵巢表达方式与腹膜病变相同；1例CK20、CK7及MUC-2阳性，MUC-1、CA125、ER及PR阴性；卵巢未予切除，阑尾为外院手术，未得到组织块；1例腹膜病变未获得组织块，影像提示双侧卵巢萎缩，而阑尾活检CK20及MUC-2阳性，CK7、MUC-1、CA125、ER及PR阴性；另1例术中见阑尾正常，未切除，腹膜及卵巢病变CK20、MUC-2、CK7、MUC-1、CA125、ER及PR均为阴性。结论腹膜假黏液瘤是一种以腹膜大量胶冻样黏液播散种植为特征的病变，患者往往具有阑尾黏液性病变，或曾行阑尾切除史。在女性患者，虽然部分病例卵巢同时有病变，但多数双侧卵巢受累，结合免疫组化检查考虑大部分腹膜假黏液瘤起源于阑尾，卵巢肿瘤应为种植而非原发，对腹膜假黏液瘤患者外科手术时应常规切除阑尾。     

黏液纤维肉瘤和低级别纤维黏液样肉瘤的诊断和鉴别诊断

黏液纤维肉瘤（myxofibmsarcoma,MFS）,尤其是其亚型,低级别黏液纤维肉瘤（low-grademyxofibmsarcoma,LGMFS）,与低级别纤维黏液样肉瘤（low-gradefibromyxoidsarcoma,LGFMS）不仅好发部位,而且命名相似,颇易相互混淆,但二者的生物学行为不同,鉴别十分必要。MFS是真性肉瘤,依其分化程度分为3级,其中LGMFS最需要与LGFMS相鉴别。LGFMS亦称为Evans瘤,曾被认为有较高的复发、转移及病死率,但现有研究表明这三方面均较过去的报道少得多。因此,LGFMS与隆突性皮肤纤维肉瘤一样,属低级别肉瘤,即一种中间型软组织肿瘤。同时,需与软组织的其他黏液性肿瘤,如肌内黏液瘤、富于细胞的黏液瘤、关节旁黏液瘤、侵袭性血管黏液瘤、浅表性血管黏液瘤、神经鞘黏液瘤以及黏液样脂肪肉瘤和黏液样隆突性皮肤纤维肉瘤等进行鉴别。在日常诊断病理学工作中,易将MFS和LGFMS误诊为软组织的其他黏液性肿瘤。因此,弄清二者的诊断标准和鉴别诊断,在实际工作中十分重要。     

胰腺囊性肿瘤的诊断及治疗研究进展:附6例病例报告

胰腺囊性肿瘤(pancreatic cystic neoplasms,PCN)主要包括浆液性囊腺瘤(serous cystic neoplasm,SCN)、黏液性囊腺瘤(mutinous cystic neoplasm,MCN)、导管内乳头状黏液性囊腺瘤(intraductal papillary mucinous neoplasm,IPMN)及实性假乳头状瘤(solid pseudopapillary neoplasm,SPN)等。近年来,随着影像学诊断技术的进展,CT与磁共振的广泛应用,胰腺囊性肿瘤的检出率较前有所提高,但尚不能完全准确区分其组织类型,也没有统一的治疗方案。影像学是PCNs鉴别诊断的主要依据。对于有明显症状、确诊或可疑恶性的PCNs,积极根治性手术治疗可提高大多数患者长期生存率。     

乳腺原发性黏液性囊腺癌临床病理分析和文献复习

目的 探讨乳腺原发性黏液性囊腺癌(mucinous cystadenocarcinoma,MCA)的临床病理特征及鉴别诊断.方法 分析1例MCA的组织病理学、免疫表型资料并复习文献.结果 乳腺肿物切面呈囊实性.镜下见大小不等、分布不均的囊性区,囊壁衬覆富含黏液的肿瘤细胞,或呈单层柱状、或复层化增生或形成乳头状结构.肿瘤细胞胞质内黏液呈PAS、AB染色阳性.肿瘤细胞CK7阳性,CK20阴性,ER、PR、HER2均阴性.囊壁肿瘤细胞外侧肌上皮细胞呈p63、SMA阴性.结论 (1)MCA是主要发生于绝经后妇女的罕见肿瘤,预后较好.(2)与卵巢和(或)胰腺黏液性囊腺癌类似,诊断原发肿瘤需先排除转移可能.     

腹膜假黏液瘤

目的;探讨腹膜假黏液瘤（PMP）的病理形态和免疫组织化学特点,病理诊断、发生及预后。方法：复习11例PMP的临床资料并进行随访,分别对线例腹膜及原发瘤进行光镜和免疫组织化学观察。结果：11例PMP男女比为3：8;年龄36－76岁（平均56岁）。随访1例术后2年死亡,1例失访,余8例1－60个月健在。11例均表现腹腔大量黏液和腹膜多发包裹黏液性肿瘤;伴有阑尾黏液性肿瘤者8例,其中5例女性同时有卵巢黏液性病变;结肠黏液性肿瘤1例,伴有卵巢黏液性病变;单纯卵巢黏液性肿瘤2例。CK7、CK20和CA125标记示同一病例其阑尾和（或）卵巢及腹膜肿瘤标记结果常一致。结论：对PMP作病理诊断时,应综合分析做出良性、低度恶性或恶性PMP的诊断。阑尾与PMP的发生可能有更加直接的关系。PMP的预后取决于其生长速度。     

肾脏黏液样小管状和梭形细胞癌临床病理分析

目的探讨肾脏黏液样小管状和梭形细胞癌（mucinous tubular and spindle cell carcinoma, MTSCCa）的临床病理特征和鉴别诊断要点及生物学行为。方法对4例MTSCCa标本进行组织病理学和免疫组化染色观察，并复习临床资料及相关文献。结果该肿瘤好发于女性，发病年龄17～82岁（平均53岁），临床症状不明显。组织学：肿瘤与周围肾组织分界清楚，切面实性、灰白色，肿瘤细胞形态呈双相（小管状和梭形细胞）或三相（小管状、梭形和脊索瘤样或黏液样）。其他组织学表现：泡沫样巨噬细胞聚集、典型的透明细胞和乳头状或乳头结构。免疫组化显示复合性免疫表型。结论MTSCCa是一种罕见的低级别多形性肿瘤，组织学谱系在不断扩大，免疫组化表型及组织学形态与乳头状肾细胞癌（PRCCa）有重叠。     

乳腺黏液表皮样癌1例

患者女, 43岁。因右乳肿块3个月行手术切除。病变切面呈囊实性。镜下观察:肿瘤呈囊实性生长, 囊内可见乳头状突起。肿瘤由形态温和的中间细胞、表皮样细胞、黏液细胞和嗜酸性细胞构成, 细胞间可见筛状腺腔/微囊结构, 其内含黏液或嗜酸性分泌物。瘤周乳腺组织可见淋巴组织增生。免疫组织化学:p63、细胞角蛋白(CK)5/6和CK7呈分区阳性染色, GATA3阳性、S-100蛋白和SMMHC阴性, 雌激素受体(ER)阳性率25%、孕激素受体(PR)阴性、HER2 1+、Ki-67阳性指数约5%。荧光原位杂交检测提示MAML2基因重排。病理诊断为右乳低级别黏液表皮样癌。     

The coexistence of low-grade mucinous neoplasms of the appendix and appendiceal diverticula: a possible role in the pathogenesis of pseudomyxoma peritonei.

We examined 38 appendectomies with diagnoses of mucocele, diverticulum, or adenoma to study the coincidence of appendiceal diverticula and appendiceal low-grade mucinous neoplasms and to examine the possible role of diverticula in the pathogenesis of pseudomyxoma peritonei. Invasive adenocarcinomas and retention cysts were excluded (six cases). Cases were classified as adenomas or mucinous tumors of unknown malignant potential, with or without diverticula. Medical records were reviewed for multiple parameters, including presenting symptoms, presence of pseudomyxoma peritonei, and presence of associated malignancies. Binomial statistics were used to calculate the probability that the observed prevalence of low-grade mucinous neoplasms and diverticula together was significantly different from the expected prevalence of diverticula or low-grade mucinous neoplasms alone, using historical controls from the literature. Twenty-five percent of the total cases (8 of 32) contained both a low-grade mucinous neoplasm (7 cystadenomas and 1 mucinous tumor of unknown malignant potential) and a diverticulum. Thus, 8 of 19 low-grade mucinous neoplasms (42%) were associated with diverticula. Of the appendices with both low-grade mucinous neoplasms and diverticula, three contained dissecting acellular mucin within the appendiceal wall, four showed diverticular perforation, and one had pseudomyxoma peritonei associated with the ruptured diverticulum. A significant percentage (P < .001) of cases contained low-grade mucinous neoplasms and diverticula together. The case of coexistent low-grade mucinous neoplasm, diverticulum, and pseudomyxoma peritonei suggests that diverticula could play a role in the pathogenesis of pseudomyxoma peritonei. This could occur either by involvement of preexisting diverticula by the neoplasm or by distention of the appendiceal lumen by mucin, leading to increased intraluminal pressure and subsequent diverticulum formation at a weak area in the wall. Either mechanism might allow low-grade mucinous neoplasms to penetrate the appendiceal wall more easily.     

SATB2 is a supportive marker for the differentiation of a primary mucinous tumor of the ovary and an ovarian metastasis of a low-grade appendiceal mucinous neoplasm (LAMN): A series of seven cases

The differentiation between a primary mucinous ovarian neoplasm and an extra-ovarian metastasis in the ovary is often challenging in the histopathologic practice. Among various ovarian metastases from the gastro-intestinal tract the low-grade appendiceal mucinous neoplasm (LAMN) is an important differential diagnosis to consider particularly in case of pseudomyxoma peritonei. A newly recognized marker in the routine diagnostic of a mucinous neoplasm in the ovary is SATB2 (Special AT-rich sequence-binding protein 2). The expression of SATB2 is, within cells of epithelial lineages, mainly restricted to the lower gastro-intestinal tract, indicating colorectal or appendiceal cancer origin. We report seven cases of LAMN, which clinically became apparent due to ovarian metastases in context of pseudomyxoma peritonei or at least small foci of peritoneal tumor spread. An immunohistochemical marker-panel including SATB2, CDX2, CK20, CK7, PAX8, ER and PR revealed a strong expression of SATB2 in all seven cases. On the contrary SATB2-negativity could be demonstrated in the 40 cases of mucinous borderline tumors and primary mucinous carcinomas of the ovary. The histopathologic tentative diagnosis of an ovarian metastasis of LAMN could be confirmed in the findings of the Appendix in six of seven cases. This report supports SATB2 as an additional diagnostic marker for the diagnosis of an ovarian manifestation of LAMN.     

Pseudomyxoma peritonei (mucinous carcinoma peritonei) preceded by intraductal papillary neoplasm of the bile duct

Pseudomyxoma peritonei (mucinous carcinoma peritonei) is a rare clinical disease. Although most cases derive from appendiceal mucinous tumors, a few are associated with pancreatic intraductal papillary mucinous neoplasms. Intraductal papillary neoplasms of the bile duct share many similarities with pancreatic intraductal papillary mucinous neoplasms and are thought to be their biliary counterparts. We report a case of low-grade intraductal papillary neoplasm of the bile duct who developed pseudomyxoma peritonei 6 years after surgical treatment of the primary biliary tumor. To the best of our knowledge, this is the first case of pseudomyxoma peritonei associated with intraductal papillary neoplasm of the bile duct. The tumor recurrence in our case may be due to tumor spillage at the time of the first surgery, since there is no recurrent biliary tumor in the preserved liver lobe. Prevention of spillage of epithelial cell-containing mucin during surgical operations is important in treating intraductal papillary neoplasms of the bile duct.     

颅外原发下颌骨脑膜瘤临床诊治一例报道并文献复习

目的 探讨颅外原发下颌骨脑膜瘤的临床病理和影像学特征,以及诊断和治疗方法。方法 回顾性分析2017年10月无锡市第二人民医院收治的1例57岁女性颅外原发下颌骨脑膜瘤患者的临床资料。在PubMed、中国知网、万方数据及维普数据库中,以“下颌骨(mandibular)”和“原发性脑膜瘤(primary meningioma)”为关键词,检索截至2017年10 月有关下颌骨原发性脑膜瘤的相关文献,共纳入7篇8例颅外原发下颌骨脑膜瘤的报道,均为英文文献;结合本例诊治过程,总结该病临床及影像学表现、组织学形态、免疫组织化学特征、治疗方法及临床预后特点。结果 本文1例中年女性下颌骨无痛性膨胀性病变,CT为境界清楚的透射影,组织学梭形肿瘤细胞伴有局部旋涡状结构,免疫组织化学瘤细胞上皮膜抗原(EMA)、波形蛋白(Vimentin)支持脑膜瘤的诊断;手术完整切除下颌骨肿瘤,术后随访9个月无复发。结合文献报道的8例共9例颅外原发下颌骨脑膜瘤,男2例、女7例,年龄20~74岁;多以下颌骨局部膨胀为主要临床表现;影像学为下颌骨境界清楚的溶骨性病变,多为透射影,也可透射和非透射混合影像;组织学同颅内脑膜瘤,为纤细梭形瘤细胞束状或旋涡状排列,细胞间丰富胶原,部分细胞多边形上皮样,胞界不清,片状分布,可见砂粒体,细胞无异形;免疫组织化学瘤细胞EMA、Vimentin均阳性,孕激素受体、广谱细胞角质蛋白、肌动蛋白结合蛋白、平滑肌肌动蛋白、结蛋白、S-100蛋白、β-微管蛋白-3、CD34、B淋巴细胞瘤-2和尤因肉瘤标记物均阴性,Ki-67增殖指数1%。治疗以肿块切除及下颌骨切除自体骨片移植为主要手术方式。组织学良性者预后好,手术切除可治愈。结论 颅外原发下颌骨脑膜瘤非常罕见,需结合临床及影像学、病理组织学进行鉴别诊断和诊断。手术完整切除肿块及下颌骨重建可治愈。     

低级别中央型骨肉瘤的临床诊治及预后分析

目的 总结低级别中央型骨肉瘤(LGCOS)的临床表现、影像学特征、组织学特点以及临床预后。方法 回顾性分析上海市第六人民医院2008年1月—2016年1月经病理学确诊的34例LGCOS患者的临床资料,其中男22例、女12例,年龄13~62岁,中位年龄40岁。28例为初发肿瘤,6例为术后复发。发病部位股骨远端11例,胫骨近端9例,股骨近端7例,肱骨近端3例,尺骨、桡骨、髂骨、腓骨各1例。所有患者行广泛性瘤段切除术,观察患者的临床表现、影像学及病理学特征、治疗及随访、预后情况。结果 LGCOS患者临床表现以疼痛或肿块为主。影像学主要表现为成骨性、溶骨性以及混合成骨,以混合成骨多见,18例中13例X线表现出2种以上的恶性征象。34例患者组织学表现温和,可见大量胶原纤维、分化相对成熟的骨样组织以及轻度异型的梭形细胞;其中11例有局灶去分化成分,表现为细胞丰富,有明显的异型性及病理性核分裂象。术后随访1~8(3.5±1.8)年,其中3例复发,2例出现转移而死亡。6名复发患者中3例行截肢治疗。结论 LGCOS是一种分化良好、恶性程度低的肿瘤,其临床特点为病程长、症状轻微;当X线表现为成骨与溶骨共存时,均应考虑到LGCOS的可能并完善CT及MRI检查;活检方式建议采取切开活检,尽可能多点取样;LGCOS的预后取决于其治疗方法,准确的诊断极其重要。     

Ovarian mucinous tumour arising in mature cystic teratoma and associated with pseudomyxoma peritonei: report of two cases and comparison with ovarian involvement by low-grade appendiceal mucinous tumour

AIMS: It is currently accepted that primary ovarian tumours rarely, if ever, give rise to mucinous ascites/pseudomyxoma peritonei (PMP) which most commonly results from the intra-abdominal spread of an appendiceal mucinous neoplasm. However, primary ovarian mucinous tumours of appendiceal type arising within mature cystic teratomas appear to represent an exception to this rule. In this report two further examples of this rare tumour are described, and the immunohistological phenotype including expression of MUC proteins is compared with secondary ovarian involvement by low-grade appendiceal mucinous neoplasm. METHODS: Two cases of ovarian mucinous tumour associated with mature cystic teratoma and PMP are described. The tumours were examined immunohistochemically for expression of cytokeratin (CK)7, CK20, carcinoembryonic antigen (CEA), CDX-2, MUC2, MUC5AC and MUC6. The results were compared with four cases of ovarian neoplasia secondary to primary appendiceal low-grade mucinous tumour. RESULTS: The ovarian mucinous tumours associated with mature cystic teratomas were morphologically similar to those secondary to appendiceal neoplasia. They comprised irregularly distributed glands and cysts lined by tall, mucin-rich epithelial cells exhibiting focal villoglandular architecture and low grade cytological atypia. The immunophenotype of the teratoma-associated tumours and those secondary to appendiceal neoplasia was identical: there was strong and diffuse expression of CK20, CEA, CDX-2, MUC2 and MUC5AC with no reactivity for the other antisera tested. CONCLUSIONS: PMP associated with primary ovarian neoplasia is rare, and probably restricted to mucinous tumours arising in mature cystic teratomas. The immunohistological findings in this study further support the view that such tumours exhibit a lower gastrointestinal and, more specifically, appendiceal phenotype. Careful examination and sampling of the ovaries may be required to demonstrate the teratomatous component of these tumours.     

Revisiting the necessity for routine appendectomies in mucinous neoplasms of the ovary: An evaluation of 460 mucinous ovarian tumors

Appendectomies are not uncommonly performed following an intraoperative diagnosis of a mucinous ovarian neoplasm, although the evidentiary basis for the practice is relatively limited. The current study is a contemporary re-examination of the issue, based on an analysis of a large single institutional cohort. We assessed whether there are any composite of factors that may be associated with the finding of significant disease in the appendix in this setting following intraoperative consultation (IOC) diagnosis of a mucinous neoplasm on an ovary-based mass. Records for 460 consecutive patients whose ovarian tumors were classified as “mucinous” on IOC (n = 246) and/or permanents (n = 214) were reviewed. The distribution of IOC diagnoses on the 246 tumors were as follows: cystadenoma (114), borderline (55), carcinoma (21), mucinous neoplasm or tumor without definitive classification (53), and probable metastases (3). Appendectomies were performed on 82 (33%) of the 246 cases. In 30 (36%) of these 82 cases, the appendix was grossly normal, the ovarian tumor was unilateral, and there was no intraabdominal/peritoneal disease. Microscopic examination of the appendices in these 30 cases showed no mucinous neoplasms therein, but one case had a grossly inapparent, 4 mm well-differentiated carcinoid. In contrast, among the remaining 52 cases (i.e. those with at least one of the “key abnormal features”: intra-abddominal/peritoneal disease and/or appendiceal gross abnormality and/or ovarian tumor bilaterality), 12 neoplasms (23%) were microscopically identified in the appendix (4 adenocarcinomas; 7 LAMN; 1 carcinoid) [p = 0.0256]. Of these 12, a grossly abnormal appendix, intraabdominal/peritoneal disease, and ovarian tumor bilaterality was the sole key abnormal feature in 10, 8 and 4 cases respectively, meaning that requiring that any one feature be present to justify the appendectomy would have missed 17%, 33% and 67% of cases respectively. Only 33% (3/12) cases had all 3 features. Our findings support the emerging body of work that indicates that appendectomies should not be routinely performed during the primary surgery for suspected or confirmed mucinous tumors that involve the ovary, unless there is a specific indication. In our cohort, all identified mucinous appendiceal neoplasms were associated with at least one key abnormal feature (gross abnormalities of the appendix, intraabdominal/peritoneal disease, ovarian tumor bilaterality), which suggests that only in patients that meet these criteria would appendectomies most likely be beneficial.     

Primary epithelial neoplasms and other epithelial lesions of the appendix (excluding carcinoid tumors)

Epithelial tumors of the appendix range from low-grade mucosal-based tumors which, when confined to the appendix, have an excellent prognosis but, once outside the appendix, have a fair prognosis and often a prolonged disease course, to high grade invasive carcinomas that are rapidly fatal. Low grade mucinous neoplasms may rupture and spread to the peritoneum as pseudomyxoma peritonei, and the nomenclature of these tumors has been the subject of considerable disagreement among pathologists; the designation "low grade appendiceal mucinous neoplasm" has recently been proposed for reasons discussed herein. Demonstrating rupture of these neoplasms may require particularly diligent gross and microscopic evaluation as the rupture site often heals over leaving only subtle evidence of its presence. Invasive adenocarcinomas are often mucinous and may also spread to the peritoneum. Against this backdrop, the clinical and pathologic features of low grade appendiceal mucinous neoplasms and mucinous adenocarcinomas, as well as other types such as typical colorectal type and signet-ring cell type, are reviewed. In addition, emerging entities, serrated polyps and serrated adenomas, whose significance is only beginning to be understood, are considered. Retention cysts, hyperplastic polyps, and diffuse mucosal hyperplasia, although not necessarily neoplastic, are reviewed here as they may enter into the differential diagnosis of appendiceal mucinous neoplasms.