Carcinomas with micropapillary morphology: clinical significance and current concepts

Invasive micropapillary carcinoma has been recently recognized as a rare but distinctive variant of carcinoma in various anatomic sites, including breast, urinary bladder, lung, and major salivary glands. Morphologically, it is characterized by small tight clusters of neoplastic cells floating in clear spaces resembling lymphatic channels. Most often this growth pattern is mixed with a variable component of conventional carcinoma or other variants. In addition to a unique morphology, tumors with invasive micropapillary growth share a high propensity for lymphovascular invasion and lymph node metastases. Patients have typically high-stage disease at presentation and a poor clinical outcome compared with that of patients with conventional carcinoma arising in the same organ site. In this article the author reviews the available literature on tumors displaying a micropapillary component.     

Fine-needle aspiration biopsy of invasive micropapillary carcinoma of the breast: a report of five cases

Invasive micropapillary carcinoma of the breast is an uncommon variant of infiltrating ductal carcinoma. Observing its distinctive cytologic appearance and aggressive behavior is important for early diagnosis by fine-needle aspiration cytology (FNAC). There are only a few reported cases in the literature. Five women presented with breast masses. FNAC showed malignant epithelial tumors, and mastectomy materials showed invasive micropapillary carcinoma for all of them. Three patients had axillary lymph node metastases. Invasive micropapillary carcinoma, with its angulated papillary clusters lacking a fibrovascular core, and irregular crowded nuclei, has a distinctive cytologic appearance which correlates with its histological features. A differential diagnosis from other primary or metastatic papillary lesions of the breast may be possible using immunohistochemistry and some cytologic features. The limited experience with invasive micropapillary carcinoma should not discourage others from undertaking further studies.     

KL-6 is another useful marker in assessing a micropapillary pattern in carcinomas of the breast and urinary bladder,but not the colon

To evaluate the peculiar “inside-out” pattern in micropapillary (MP) carcinoma, we investigated the usefulness of KL-6 antibody in the assessment of the MP pattern of cancers, in comparison with antibodies to epithelial membrane antigen (EMA), MUC1 (CD227), and CD 10. Immunohistochemical investigation was performed on specimens exhibiting an MP pattern obtained from 12 persons with cancer: 4 with breast carcinoma, 3 with carcinoma of the urinary bladder, and 5 with colonic carcinoma. Immunohistochemical study with KL-6, EMA, and MUC1 antibodies revealed similar continuous linear positive patterns restricted to the surface of the MP pattern in both breast and urinary bladder cancers, revealing the peculiar “inside-out” morphology. However, EMA also gave cytoplasmic positivity in most of the cases tested, and MUC1 was also present in the cytoplasm of some cases. In sharp contrast, immune reactions of colon carcinomas with these antibodies were negative, except for focal positivity for KL-6 and MUC1 antibodies in some cases. CD10 was only focally positive in an MP pattern in 4 of the 5 cases of colon carcinoma and in 1 case with carcinoma of the urinary bladder. These findings suggest that KL-6 is a useful marker to assess the MP character of breast and urinary bladder carcinomas; that MUC1 was similarly positive, with the addition of cytoplasmic positivity in some cases; and that the MP pattern of colon cancer, positive for CD 10, was different in character from both breast and urinary bladder carcinomas, although all these cancers seemingly exhibit similar MP patterns on histopathology. This heterogeneity of the MP pattern in various cancers needs to be investigated when more cases have been accumulated.     

Metaplastic variant of invasive micropapillary breast carcinoma: a unique triple negative phenotype

Invasive micropapillary carcinomas (IMC) and metaplastic breast carcinoma (MBC) have different clinicopathologic features. This study reports an unusual case of multifocal grade III IMC associated with MBC component in a 35-year-old woman. MBC was vimentin positive, pancytokeratin negative, and showed focal p63 positivity. Immunostains for estrogen and progesterone receptor, and fluorescence in situ hybridization for Her2/neu amplification were negative. All the left axillary lymph nodes dissected were positive for metastatic carcinoma with ductal and IMC patterns, but without metaplastic component. Postmastectomy computed tomography and magnetic resonance imaging scans showed metastases to lungs, liver, brain, and vertebrae. The biologic behavior of tumor was in accordance with histology, so that the nodal and distant metastases were testament to the underlying inherently aggressive IMC, whereas large tumor size and triple negativity reflected the features of MBC. To the best of the authors' knowledge, this is the first report of a metaplastic variant of invasive micropapillary breast carcinoma with triple negative phenotype.     

Primary invasive micropapillary carcinoma of the stomach

Reported herein is the case of a 74-year-old man with an unusual gastric carcinoma that developed at the lesser curvature of the stomach. The tumor consisted of small clusters of carcinoma cells surrounded by clear spaces, with histopathology similar to invasive micropapillary carcinoma (IMPC) of the breast. The carcinoma cells, which had downregulation of E-cadherin expression, invaded the subserous tissue and metastasized to the perigastric lymph nodes. IMPC, an unusual subtype of invasive breast carcinoma, is known to have frequent lymph node metastases, resulting in a poor clinical outcome. Although IMPC has been reported in breast, urinary bladder, ureter, lung, salivary gland and colon, to the best of the authors' knowledge this is the first report of IMPC arising in the stomach. Presented here are the clinicopathological features of primary IMPC of the stomach.     

Primary invasive micropapillary carcinoma of the colon

AIMS: Invasive micropapillary carcinoma (IMPC) is associated with frequent lymph node metastasis and adverse clinical outcome. IMPC has been reported in breast, urinary bladder, ureter, lung and parotid gland but not in colon. We present the clinicopathological features of three cases of primary IMPC of the colon with a review of the literature. METHODS AND RESULTS: The patients (one man and two women) were 53, 67 and 68 years old, respectively. The size of the tumour ranged from 20 to 100 mm in diameter. Histologically, all cases were composed predominantly of papillary tumour cell clusters with spaces in a background of fine fibrocollagenous stroma. One of the tumours (case 1) was nearly completely composed of IMPC, but the other two were associated with foci of adenocarcinoma and concurrent mucinous carcinoma, respectively. MUC1 was positive in all cases, suggestive of reverse cell orientation which is responsible for its unique histological features. CONCLUSIONS: We report three cases of primary IMPC of the colon. Its clinical significance remains undetermined but the presence of this component may represent a poor prognostic factor.     

Prognostic significance of micropapillary pattern in pure mucinous carcinoma of the breast

Breast carcinoma with micropapillary architecture is associated with aggressive behavior. Similar micropapillary pattern in pure mucinous carcinoma has been noticed and has been shown to convey poor prognosis. In this study 17 cases of pure mucinous carcinoma of the breast seen during a 10-year period have been reviewed, with special reference to micropapillary pattern. Diffuse micropapillary pattern was seen in 6 of 17 cases of mucinous carcinoma of the breast and demonstrated reverse polarity immunostaining pattern with "Epithelial Membrane Antigen." In all cases, the tumor cells showed grade I morphology, and no lymph node metastases were noticed. All the tumors except 1 expressed strong estrogen and progesterone receptor expression, however, all the cases were negative for Her-2/neu expression. In this present study, mucinous carcinomas with micropapillary pattern showed a low nuclear grade, higher incidence of hormone receptor positivity, and lower incidence of Her-2/neu similar to mucinous carcinomas without micropapillary pattern, thus explaining their indolent behavior.     

Breast carcinoma with micropapillary features: clinicopathologic study and long-term follow-up of 100 cases

To study the clinicopathologic characteristics and prognosis of invasive micropapillary carcinoma of breast (IMPC), 100 cases of invasive breast carcinoma with an IMPC component were reviewed. Compared with invasive ductal carcinoma, not otherwise specified, with similar histologic grades, carcinomas with IMPC were larger sized, had a higher lymph node metastasis rate with more nodes involved per case, and exhibited increased lymphovascular invasion. The presence of IMPC strongly correlated with the more aggressive behavior. No significant association was established between the proportion of the IMPC component and overall tumor size, histologic grade, lymph node metastasis rate, and distant metastasis, but a trend was noted. Long-term follow-up demonstrated a poorer 5-year and 10-year survival rate for patients with breast carcinoma containing an IMPC component. Breast carcinomas with micropapillary features are more aggressive tumors with a poorer prognosis. This specific structure should be carefully evaluated in the surgical pathology examination of breast carcinoma specimens.     

Cytological features of lung adenocarcinoma with micropapillary pattern in the pleural or pericardial effusion: analysis of 5 cases

Micropapillary pattern is a distinct histopathological pattern, and usually shows a high frequency of lymphatic invasion and lymph node metastases. This pattern is also reported in lung adenocarcinoma, however, only one cytological report of lung adenocarcinoma with micropapillary pattern has been reported. In this study, we analyzed the cytological features of this type of carcinoma in the pleural or pericardial effusion. This study was comprised of 5 consecutive cases of lung adenocarcinoma with micropapillary pattern, in which the tumor cells were present in the pleural or pericardial effusion and whose diagnoses were histopathologically confirmed. The characteristic cytological findings in the pleural or pericardial effusion were as follows: i) tightly cohesive small nests of tumor cells showing papillary structure without fibrovascular core, ii) these nests were comprised of approximately 5-20 tumor cells, iii) cauliflower-like and acinar-like structures were also observed, iv) intracytoplasmic vacuoles were observed in 40% of the cases, and v) the neoplastic cells had large round to oval nuclei containing coarse chromatin and occasional conspicuous nucleoli. It has been reported that the presence of micropapillary structure and intracytoplasmic vacuolation are also characteristic cytological features of micropapillary carcinoma of the urinary bladder, therefore, they are thought to be common cytological features of carcinomas with micropapillary pattern. Consequently, detection of these features can lead to a cytodiagnosis of lung adenocarcinoma with micropapillary pattern in the pleural or pericardial effusion. Recognition of these features is important because this type of tumor shows an aggressive clinical course.     

A rare case of colorectal micropapillary carcinoma

Micropapillary carcinoma is regarded as an aggressive variant of adenocarcinoma in any location. It is histologically characterized by papillary cell clusters surrounded by clear spaces. The reported proportion of micropapillary carcinoma component in the entire tumor ranges from 5-80% and no pure cases have been reported. To date, there are approximately 130 cases reported in the colorectum. We recently examined a patient with a pure micropapillary carcinoma showing co-expression of CK7, CK20, and absence of CDX2, which had an aggressive tumor with extensive perineural, vascular, and lymphatic invasion as well as extensive nodal metastasis. The presence of a micropapillary carcinoma in the colorectum seemed to be closely related with nodal metastasis, as observed in micropapillary carcinomas from other organs. Thus, if a micropapillary component is identified in a tumor, particularly in a biopsy specimen, extensive surgical resection should be considered due to the high potential for nodal metastasis, even if the preoperative diagnosis is a pedunculated early colorectal cancer.     

Intracytoplasmic lumina in invasive micropapillary carcinoma of the lung

Micropapillary carcinoma of the lung is a rare neoplasm, and several reports on micropapillary carcinoma of the lung have been presented to date. We present a case of micropapillary carcinoma of the lung here. A 75-yr-old Japanese man received the medical checkup and his chest X-ray disclosed the abnormal shadow of the lower lobe of the left lung. The histological examination of resected lung and extirpated lymph node showed the finding of micropapillary carcinoma. Some neoplastic cells of primary site contained intracytoplasmic lumina positive for Alcian blue and PAS stains. Pleural effusion appeared 9-mo after the operation. The cytology of pleural effusion showed cohesive clusters of neoplastic cells consisting of 3-20 cells without fibrovascular core. Additionally, intracytoplasmic lumina were observed in some neoplastic cells. Finally, carcinoma cells with micropapillary morphology may possess the intracytoplasmic lumina in the cytoplasm of metastatic site as well as primary site.     

The expression of Wilms' tumour-1 and Ca125 in invasive micropapillary carcinoma of the breast

AIM: Metastases from ovarian serous papillary carcinoma to the breast and primary invasive micropapillary carcinoma of the breast are histologically similar. The distinction is clinically important to ensure appropriate management. Wilms' tumour-1 (WT1) and Ca125 are frequently expressed in serous papillary carcinomas, and uncommonly in unselected mammary carcinomas. One previous study found Ca125 expression in 69% of invasive micropapillary carcinomas. The aim was to assess the frequency of expression of WT1 and Ca125 in invasive micropapillary carcinoma. METHODS AND RESULTS: Twenty-five of 34 invasive micropapillary carcinomas showed no nuclear expression of WT1. The remaining nine tumours showed weak to moderate immunoreactivity in 1-10% of nuclei. Six of these nine tumours also contained ductal carcinoma in situ, which expressed WT1 in five of the six. Membranous or cytoplasmic expression of Ca125 was found in seven tumours. CONCLUSION: Nuclear WT1 expression is present in a minority of invasive micropapillary carcinomas and, when present, expression is focal. The frequency of expression of Ca125 was similar to the results in unselected mammary carcinoma. Thus, these markers are useful members of the immunohistochemical panel for the distinction of mammary invasive micropapillary carcinoma from ovarian serous papillary carcinoma.     

乳腺浸润性微乳头状癌临床病理因素的研究现状

目的 探讨年龄、肿瘤大小、组织学及核分级、腋淋巴结、激素受体、生长因子受体及细胞增值率等临床病理因素在乳腺浸润性微乳头状癌（IMPC）发生、发展、转移及预后的评估中的意义.方法 应用Pubmed及CNKI数据库系统以“IMPC”为关键词检索文献,筛选出相关一次文献,对文献进行分析.结果 IMPC中肿瘤大小、IMPC成分的比例、共存病灶的病理类型和组织学分级均与淋巴结转移的发生率无关;IMPC独特的形态学特征和间质淋巴细胞浸润可能是其高侵袭性的原因所在;IMPC中雌激素受体（ER）和人类表皮生长因子受体2（HER2）阳性表达比率高,其中,ER阳性表达可作为一个积极预后指标.结论 对IMPC这一特殊亚型认识还比较肤浅,随着研究的不断深入,IMPC的诊治状况将得到进一步的改观.     

Colorectal adenocarcinoma with micropapillary pattern and its association with lymph node metastasis.

Micropapillary carcinoma has been reported as an aggressive variant of carcinoma in several organs, where it is associated with frequent lymphovascular invasion and poor clinical outcome. This study explored the clinicopathological features of colorectal adenocarcinoma with a micropapillary carcinoma component and compared them with those of conventional colorectal adenocarcinoma. One hundred seventy-eight consecutive cases of surgically resected colorectal carcinomas were studied for tumor size, type, depth of invasion, nodal and distant metastases, tumor stage, and percentage and extent of micropapillary component. Among 178 cases of colorectal carcinoma, 34 (19.1%) cases had a micropapillary component, which ranged from 5 to 60% of the entire tumor. Lymph node metastasis was identified in 25 of 34 (73.5%) carcinomas with micropapillary component, whereas they were detected in 61 of 144 (42.4%) cases without micropapillary component (P=0.001). Lymphovascular invasion was identified more frequently in carcinoma with micropapillary component (41.2%) than carcinoma without micropapillary component (20.1%; P<0.05). Distant metastases occurred in 4 of 34 cases (11.7%) with micropapillary component and in 10 of 144 cases (6.9%) without micropapillary component (P=0.311). Multivariate regression analysis demonstrated that the presence of micropapillary component, as well as tumor stage and lymphovascular invasion are independent predictors of regional nodal metastasis.     

Aggressive invasive micropapillary salivary duct carcinoma of the parotid gland

The presence of invasive micropapillary component has been reported to be associated with salivary duct carcinoma and poor outcomes. Herein is described a rare case of invasive micropapillary salivary duct carcinoma of the parotid gland in a 60-year-old man. The micropapillary component was approximately 70% of the area of the tumor. Squamous differentiation was focally seen adjacent to the micropapillary component. On immunohistochemistry the ordinary salivary duct carcinoma component was positive for gross cystic disease fluid protein-15 (GCDFP-15), androgen receptor (AR), and HER2/neu, whereas both micropapillary and squamous components were negative for GCDFP-15 and AR. Immunohistochemical staining for D2-40 highlighted the lymph vessel invasion of tumor cells. This patient developed metastases in the lymph nodes of the neck, and also in the liver, lung, and brain. The lymph nodes and liver metastases had both ordinary salivary duct carcinoma and micropapillary components. The patient died of tumor 11 months after the initial surgical operation. The results support that the presence of micropapillary component is associated with more aggressive behavior of salivary duct carcinoma. It is also important for pathologists to recognize that GCDFP-15 and AR expression can be reduced in micropapillary carcinoma in the differential diagnosis of metastatic tumor.