Mucinous carcinoma of the breast: a multifaceted study with special reference to histogenesis and neuroendocrine differentiation

Mucinous carcinoma of the breast: a comparative study on cytohistological findings associated with neuroendocrine differentiation

OBJECTIVE

Mucinous carcinoma (MCA) may show neuroendocrine differentiation (ND), but the cytological features characteristic of ND remains elusive. We compared fine needle aspiration (FNA) findings of MCA between cases with high and low degrees of ND.

METHODS

Histological sections of 37 MCA cases were immunohistochemically evaluated for expression of chromogranin A and synaptophysin, and were graded as 0 to 3+ degrees of ND. They were divided into low ND (grade 0 and 1+) and high ND (grade 2+ and 3+) groups. Pre-operative FNA samples of each group were assessed for cytological features.

RESULTS

The mean age of the high ND group (n = 18) was higher than the low ND group (n = 19, P = 0.01). In FNA samples of the high ND group, 17 cases showed moderate to severe degrees of discohesiveness, but low ND cases mainly showed no or only mild discohesiveness (P < 0.001). Nine of the low ND cases displayed overlapped, cohesive cell clusters, whereas, in the high ND cases, the cells were arranged in a loose, flat and monolayered pattern (P = 0.045). Fourteen of the high ND cases had round nuclei, but oval nuclei were predominant in the low ND cases (P = 0.027). The nuclei were eccentrically located in 12 of the high ND cases but were centrally located in 14 of the low ND cases (P = 0.01).

CONCLUSIONS

Mucinous carcinoma with high ND may be diagnosed by the presence of discohesiveness, a flat, monolayered pattern, and round or eccentrically located nuclei. Features of ND in carcinomas in other organs, such as intracytoplasmic granules and coarse chromatin, may not be reliable cytological features of ND in MCA.

Morphological features and mucin expression profile of breast carcinomas with signet-ring cell differentiation

Signet-ring cells are relatively common in breast cancers but are frequently overlooked. Although previously defined as a subtype of mucin producing carcinomas, breast carcinomas with signet-ring cell (SRC) differentiation nowadays are not considered a distinct entity. The objective of the present study was to characterize the morphological features and mucin expression profile of breast carcinomas with SRC differentiation. All breast carcinomas diagnosed at Centro Hospitalar S. Joao between 1996 and 2006 in which the pathology report mentioned the presence of SRCs (n=11) and four mucinous carcinomas were included in the study. The frequency of SRCs and immunohistochemistry expression of MUC1/MUC2/MUC5AC/MUC6 were evaluated. We confirmed that SRC differentiation can occur in different histological types, including ductal, lobular, mucinous and metaplastic carcinomas. The proportion of SRCs was highly variable (range: 8-70%). Tumors encompassed SRCs of intracytoplasmic lumina and goblet-cell type. A higher percentage of SRCs was associated with lymphovascular invasion (p=0.047). All tumors expressed cytoplasmic and membranous MUC1. Secretory mucins were more frequent in mucinous carcinomas and in carcinomas with extensive SRC differentiation. We conclude that besides the usefulness of mucin immunodetection for the differential diagnosis of carcinomas with SRC differentiation of breast origin, it is important to report SRC differentiation regardless of histological type because of its intrinsic prognostic value.

Mucinous breast carcinoma with a lobular neoplasia component: a subset with aberrant expression of cell adhesion and polarity molecules and lack of neuroendocrine differentiation

We investigated whether some mucinous carcinomas (MUCs) are associated with lobular neoplasia (LN) components, and if so, whether this subset has any distinct biological properties. MUC specimens from 41 patients were stratified into pure and mixed types. The LN components adjacent to MUC lesions were examined histopathologically. We also tested immunohistochemically for E-cadherin, β-catenin, and the neuroendocrine markers chromogranin A and synaptophysin; and compared results between MUCs with and without LN. Of 41 patients with MUC, LN was detected in 12 patients (29%); LN alone was the noninvasive component in 8 patients (20%). Decreased E-cadherin and β-catenin expression in the MUC component was detected in 2 (17%) and 7 (58%) cases, respectively, of MUC with LN, compared with 0% (P = 0.080) and 21% (P = 0.018) in MUCs without LN. Neuroendocrine factors were frequently detected in MUCs with LN (42%) and without LN (52%), but tended to be less frequent in MUCs with only LN components (25%) than in other MUCs (55%; P = 0.133). MUCs associated with LN components appear to be a biologically characteristic subset that frequently shows decreased cell-cell adhesion, cell polarity molecules and lack of neuroendocrine differentiation.

CDX-2, MUC-2 and B-catenin as intestinal markers in pure mucinous carcinoma of the breast

Background

Pure mucinous adenocarcinoma of the breast is a rare entity characterized by the production of variable amounts of mucin comprising 1% to 6% of breast carcinomas. Some mucinous adenocarcinomas have shown expression of intestinal differentiation markers such as MUC-2. This study examines the expression of intestinal differentiation markers in this type of breast carcinoma.

Results

Twenty-two cases of pure mucinous adenocarcinoma of the breast were assessed. Immunochemistry was performed for beta-catenin, CDX-2 and MUC-2. All cases were positive for B-catenin. MUC-2 positivity was observed in all cases; 63. 6% were 3 plus positive. All cases were negative for CDX-2.

Conclusions

These results suggest that mucinous breast carcinomas express some markers of intestinal differentiation, such as MUC-2 and beta-catenin; however, future studies with a larger series of cases and using molecular techniques that help affirm these results are needed.

Lynch syndrome-associated breast cancers do not overexpress chromosome 11-encoded mucins

Mismatch repair-deficient breast cancers may be identified in Lynch syndrome mutation carriers, and have clinicopathological features in common with mismatch repair-deficient colorectal and endometrial cancers such as tumour-infiltrating lymphocytes and poor differentiation. Mismatch repair-deficient colorectal cancers frequently show mucinous differentiation associated with upregulation of chromosome 11 mucins. The aim of this study was to compare the protein expression of these mucins in mismatch repair-deficient and -proficient breast cancers. Cases of breast cancer (n=100) were identified from families where (1) both breast and colon cancer co-occurred and (2) families met either modified Amsterdam criteria or had at least one early-onset (<50 years) colorectal cancer. Tumour sections were stained for the epithelial mucins, MUC2, MUC5AC, MUC5B and MUC6, and the homeobox protein CDX2, a regulator of MUC2 expression. In all, 16 mismatch repair-deficient Lynch syndrome breast cancers and 84 non-Lynch breast cancers were assessed for altered mucin expression. No significant difference in the expression of MUC2, MUC5AC or MUC6 was observed between the mismatch repair-deficient and mismatch repair-proficient breast cancers; however, there was a trend for mismatch repair-deficient tumours to express high levels of MUC5B less frequently (P=0.07, OR=0.2 (0.0-1.0)). Co-expression of two or more gel-forming mucins was common. Ectopic expression of CDX2 was associated with expression of MUC2 (P=0.035, OR=8.7 (1.3-58.4)). Mismatch repair-deficient breast cancers do not show differential expression of the mucins genes on chromosome 11 when compared with mismatch repair-proficient breast cancers, in contrast with mismatch repair-deficient colorectal and endometrial cancers, which frequently have increased mucin protein expression when compared with their mismatch repair-proficient counterparts. In addition, ectopic CDX2 expression is positively associated with de novo MUC2 expression.

Estrogen switches pure mucinous breast cancer to invasive lobular carcinoma with mucinous features

Mucinous breast cancer (MBC) is mainly a disease of postmenopausal women. Pure MBC is rare and augurs a good prognosis. In contrast, MBC mixed with other histological subtypes of invasive disease loses the more favorable prognosis. Because of the relative rarity of pure MBC, little is known about its cell and tumor biology and relationship to invasive disease of other subtypes. We have now developed a human breast cancer cell line called BCK4, in which we can control the behavior of MBC. BCK4 cells were derived from a patient whose poorly differentiated primary tumor was treated with chemotherapy, radiation and tamoxifen. Malignant cells from a recurrent pleural effusion were xenografted in mammary glands of a nude mouse. Cells from the solid tumor xenograft were propagated in culture to generate the BCK4 cell line. Multiple marker and chromosome analyses demonstrate that BCK4 cells are human, near diploid and luminal, expressing functional estrogen, androgen, and progesterone receptors. When xenografted back into immunocompromised cycling mice, BCK4 cells grow into small pure MBC. However, if mice are supplemented with continuous estradiol, tumors switch to invasive lobular carcinoma (ILC) with mucinous features (mixed MBC), and growth is markedly accelerated. Tamoxifen prevents the expansion of this more invasive component. The unexpected ability of estrogens to convert pure MBC into mixed MBC with ILC may explain the rarity of the pure disease in premenopausal women. These studies show that MBC can be derived from lobular precursors and that BCK4 cells are new, unique models to study the phenotypic plasticity, hormonal regulation, optimal therapeutic interventions, and metastatic patterns of MBC.

Solid papillary carcinoma of the breast: imprint cytological and histological findings

Solid papillary carcinoma is a rare breast lesion, but this entity remains poorly recognized. In this article, we report a case of solid papillary carcinoma of the breast with focus on cytological and histological findings. A 66-year-old Japanese woman presented with nipple discharge. Imprint cytology obtained from the surgically resected breast specimens showed a plasmacytoid appearance and spindle cell morphology with low-grade atypia. Histologically, the tumor revealed findings of solid papillary carcinoma and predominantly showed an intraductal lesion with focal minimal invasion into the breast parenchyma. Fibrovascular cores with hyalinization were seen. Proliferation of short spindle cells was also focally observed. Pseudorosette formation or nuclear palisading at the stromal-glandular interface was seen, and intracellular or extracellular mucin deposition was occasionally identified. Nuclear atypia generally showed low grade. Finally, clinicians, cytotechnologists, and pathologists should recognize this rare tumor entity because this tumor is a malignant neoplasm showing characteristic pathological findings.

Mucinous Lesions of the Breast

Breast lesions associated with extracellular mucin production are uncommon and constitute a wide spectrum of lesions ranging from benign cyst to mucinous carcinoma. Intracytoplasmic mucin can be seen rarely in benign metaplasias but is a common finding in invasive and in situ carcinomas. In this article, we discuss the differential diagnosis of breast lesions associated with mucin production and other entities that show histologic changes that mimic mucin production.

The HER-2 receptor and breast cancer: ten years of targeted anti-HER-2 therapy and personalized medicine

The human epidermal growth factor receptor (HER-2) oncogene encodes a transmembrane tyrosine kinase receptor that has evolved as a major classifier of invasive breast cancer and target of therapy for the disease. The validation of the general prognostic significance of HER-2 gene amplification and protein overexpression in the absence of anti-HER-2 targeted therapy is discussed in a study of 107 published studies involving 39,730 patients, which produced an overall HER-2-positive rate of 22.2% and a mean relative risk for overall survival (OS) of 2.74. The issue of HER-2 status in primary versus metastatic breast cancer is considered along with a section on the features of metastatic HER-2-positive disease. The major marketed slide-based HER-2 testing approaches, immunohistochemistry, fluorescence in situ hybridization, and chromogenic in situ hybridization, are presented and contrasted in detail against the background of the published American Society of Clinical Oncology-College of American Pathologists guidelines for HER-2 testing. Testing issues, such as the impact of chromosome 17 polysomy and local versus central HER-2 testing, are also discussed. Emerging novel HER-2 testing techniques, including mRNA-based testing by real-time polymerase chain reaction and DNA microarray methods, HER-2 receptor dimerization, phosphorylated HER-2 receptors, and HER-2 status in circulating tumor cells, are also considered. A series of biomarkers potentially associated with resistance to trastuzumab is discussed with emphasis on the phosphatase and tensin homologue deleted on chromosome ten/Akt and insulin-like growth factor receptor pathways. The efficacy results for the more recently approved small molecule HER-1/HER-2 kinase inhibitor lapatinib are also presented along with a more limited review of markers of resistance for this agent. Additional topics in this section include combinations of both anti-HER-2 targeted therapies together as well as with novel agents including bevacizumab, everolimus, and tenespimycin. A series of novel HER-2-targeting agents is also presented, including pertuzumab, ertumaxomab, HER-2 vaccines, and recently discovered tyrosine kinase inhibitors. Biomarkers predictive of HER-2 targeted therapy toxicity are included, and the review concludes with a consideration of HER-2 status in the prediction of response to non-HER-2 targeted treatments including hormonal therapy, anthracyclines, and taxanes.

Neovascularization in mucinous ductal carcinoma in situ suggests an alternative pathway for invasion

AIMS

Ductal carcinoma in situ (DCIS) associated with invasive mucinous carcinoma (IMC) has not been well characterized. The aim was to characterize mucinous DCIS (mDCIS) of the breast and to describe, to our knowledge for the first time, neovascularization in mucin.

METHODS AND RESULTS

The pathology reports and slides were reviewed from 44 patients treated between 2003 and 2006 at The University of Texas M. D. Anderson Cancer Center, whose diagnosis fulfilled the criteria of IMC or DCIS with mucin production. The patients, all female, had a mean age of 62 years. DCIS was present in 93% of cases and the predominant histological types were solid, cribriform and micropapillary. The DCIS was grade 1 in 12 of 41 cases (29.3%), grade 2 in 25 of 41 cases (61%) and grade 3 in four of 41 cases (9.8%). Mucin was seen in the lumen of the ducts involved by DCIS in 88% of cases, mucin and vessels in 63.4% of cases and neither mucin nor vessels in 12.2%. The DCIS was vascular endothelial growth factor-positive, platelet-derived growth factor receptor-beta-positive and CDX-2-negative (100%). Occasional luminal cells within the DCIS were immunopositive for CD68.

CONCLUSIONS

A significant number of mDCIS showed neovascularization in intraluminal mucin. When identified on core needle biopsy, the presence of vascularized mucin should not be used alone to discriminate between invasive and in situ carcinoma. A hypothesis proposed for the source of recruitment of vessels in the mucin is that mucin can promote neovascularization and that tumour cells invade not into the adjacent fibroconnective tissue, but rather into the mucinous, richly vascularized stroma that they have induced. Alternatively, it is possible that both cells and their secretory product invade together. To our knowledge, this is the first study to characterize neovascularization within the mucinous component of DCIS associated with and without IMC.

A retrospective review with long term follow up of 11,400 cases of pure mucinous breast carcinoma

BACKGROUND

Pure mucinous breast carcinoma (PMBC) is a rare histologic type of mammary neoplasm. It has been associated with a better short-term prognosis than infiltrating ductal carcinoma (IDC) but identical long-term survival curves have been reported. The value of tumor size for TNM staging has been challenged because of the mucin content of the lesions. This study presents a large PMBC series with 20 years follow up as compared to IDC. The relative significance of a variety of common prognostic factors is calculated for this uncommon histology.

MATERIALS AND METHODS

A retrospective analysis of all PMBC cases reported in the SEER database between 1973 and 2002 was conducted. Overall survival (OS) and disease specific survival (DSS) were calculated at 5, 10, 15 and 20 years of follow up. Those curves were compared with all the IDC cases reported into the database during the same period. The prognostic significance of gender, race, laterality, age at diagnosis, T and N status, estrogen and progesterone receptors and administration of radiation therapy was calculated by univariate and multivariate analysis.

RESULTS

There were 11,422 PMBC patients reported. The median age at diagnosis was 71 years (Range 25-85). Fifty three percent of the tumors were well differentiated, 38% were moderately differentiated and the remaining 9% were poorly differentiated or anaplastic. The majority of the tumors were located in the upper outer quadrant (44%) the other 56% were roughly evenly divided between the upper inner, lower inner, lower outer and central quadrants. Eighty six percent of the patients had only localized disease at the time of surgery without nodal or distant disease while 12% had regional nodal involvement and 2% had distant metastases. The PMBC cases showed a better differentiation with lesions of lesser grade and more frequent ER/PR expression, smaller size and lesser nodal involvement when compared to the IDC cases of the same period. Kaplan Meier survival curves revealed a 5 years. breast cancer specific survival rate of 94%. Although slowly decreasing with time, 10, 15 and 20 years survival were 89%, 85% and 81% respectively compared to 82% (5 year), 72% (10 year), 66% (15 year) and 62% (20 year) for IDC. There were no significant differences in overall survival. Multivariate analysis by Cox regression revealed the nodal status (N) to be the most significant prognostic factor followed by age, tumor size (T), progesterone receptors and nuclear grade. Disease specific survival curves stratified for nodal status revealed a highly significant difference between node negative and node positive patients. The addition of radiation therapy after surgery did not significantly improve overall survival.

CONCLUSIONS

This large retrospective comparative analysis confirms the less aggressive behavior of PMBC compared to IDC. This favorable outcome is maintained after 20 years. This tumor presents typically in older patients and is rarely associated with nodal disease. Positive nodal status appears to be the most significant predictor of worse prognosis.

Expression of mucins (MUC1, MUC2, MUC3, MUC4, MUC5AC and MUC6) and their prognostic significance in human breast cancer

Mucins are a large family of glycoproteins expressed by many epithelial cells and their malignant counterparts. Much interest has been focused on expression of its members in breast cancer because of their potential role as prognostic indicators and their involvement in cancer therapy. We have examined 1447 cases of invasive breast carcinoma with a long-term follow-up, using tissue microarray (TMA) technology and immunohistochemistry to evaluate the expression profiles of several mucins (MUC1, MUC2, MUC3, MUC4, MUC5AC and MUC6) and to assess their prognostic value. We detected MUC1 expression in 91% of tumours. MUC1 overexpression was associated with a lower grade, smaller tumour size, a higher oestrogen receptor (ER)-positive phenotype and absence of both regional recurrence and distance metastasis. The subcellular localization but not the level of expression had a prognostic value in predicting outcome. The aberrant cytoplasmic and membranous localization of MUC1 was associated with poor outcome compared with apical localization, which is the normal physiological site of expression. MUC2 expression was noticed in only 8.3% of all cases and was restricted to the cytoplasm of the tumour cells. An inverse trend was identified between MUC2 expression and lymph node stage and vascular invasion status. On excluding cases of mucinous carcinoma from the analysis, the inverse association with vascular invasion was still defined and in addition an inverse association with ER status emerged. MUC3 expression was detected in 91% of cases and its expression was associated with increased local recurrence, and lymph node stage. The membranous expression of MUC3 was found to be a potentially poor prognostic feature, with higher grade and poorer Nottingham Prognostic Index (NPI), and negative ER expression. MUC4, MUC5AC and MUC6 were expressed in 95, 37 and 20% of cases, respectively. Apart from an association between MUC4 expression and tumour grade and between MUC6 and ER-negative tumours, no other associations with any clinicopathological variables were found. Apart from the higher expression of MUC2 and MUC6 in mucinous carcinomas, no association was found between the expression of different mucins and tumour type. No association between the level of expression of any of the studied mucins and patient outcomes has been identified. In conclusion, most breast carcinomas express MUC1, MUC3 and MUC4. Among the various mucins expressed in breast cancer, MUC1 and MUC3 are potential prognostic indicators, MUC1 having the strongest relationship with patient outcome.

Mucinous cystadenocarcinoma of the breast coexisting with infiltrating ductal carcinoma

A recently described and rare variant of breast carcinoma, mucinous cystadenocarcinoma (MCA), is reported in a 65-year-old post-menopausal woman. She presented with a gradually enlarged breast tumor. A well-circumscribed tumor measuring about 3 cm in diameter was noted in the mammographic and ultrasonographic examinations. The mammographic and ultrasonographic findings were indistinguishable from more common mucinous carcinoma (colloid carcinoma) of the breast. The gross appearance of the tumor was well-defined and cystic, consisting of abundant transparent to bloody mucin, as well as whitish solid parts. Microscopically, the tumor was characterized by abundant extracellular and intracellular mucin. It looked like a mucinous cystic neoplasm of the ovary and pancreas. Particularly, few microscopic foci of ordinary intermediate-grade infiltrating ductal carcinoma (IDC) and ductal carcinoma in situ (DCIS) were observed around the main lesion in this case. A transition from ordinary DCIS to MCA in situ was found. It might indicate MCA derives from a metaplasia process of ordinary DCIS. MCA can be easily differentiated from mucinous carcinoma by quite different histologic and immunohistochemical findings. According to the previously reported and present cases, MCA of the breast more commonly affects elderly women and has a relatively favorable prognosis.

Neuroendocrine differentiation in pure type mammary mucinous carcinoma is associated with favorable histologic and immunohistochemical parameters

Mucinous carcinoma of the breast is a specific good prognostic type malignancy occurring in elderly patients. Neuroendocrine differentiation has long been described in mucinous carcinoma, but the significance of such finding is uncertain. We evaluated the neuroendocrine differentiation profiles of 38 cases of pure mucinous carcinoma and compared the clinicopathological differences between those with and those without neuroendocrine differentiation. The parameters assessed included patients' age, tumor size, nuclear grade, axillary lymph node status at time of diagnosis, percentage area of intratumoral mucin, and the expression of estrogen and progesterone receptors, cerbB2 oncoprotein, and three neuroendocrine markers, namely neurone-specific enolase, chromogranin, and synaptophysin by immunohistochemistry. Patients' outcome and follow-up period were also documented. Of the 38 cases of pure mucinous carcinoma, 28, 11 and six cases showed positive staining for 1, 2 and 3 of the neuroendocrine markers. For all the groups with variable neuroendocrine differentiation and compared to those without such differentiation, they all showed older patients' age, higher proportion of tumors with lower nuclear grade, lower incidence of axillary lymph node metastasis, a higher progesterone receptor, and lower cerbB2 oncoprotein expression. No difference was detected between tumor size, intratumoral mucinous area, and estrogen receptor status. In all, 37 patients did not have distant metastases or local recurrences at the end of follow-up period, while one patient with coexisting high-grade ductal carcinoma in situ at time of diagnosis died of breast carcinoma. Our findings suggest that the identification of neuroendocrine differentiation in pure mucinous carcinoma is associated with more favorable histologic and immunohistochemical parameters.

Composite type of breast carcinoma with endocrine differentiation: a cytological and immunohistochemical study

We describe a case of breast carcinoma with endocrine differentiation containing a mixture of three different histological features that occurred in a 71-year-old woman. Histologically, the tumor was predominantly intraductal, but slightly invasive. In the intraductal lesion, the tumor consisted mainly of ovoid to round cells with a modest to abundant amount of granular eosinophilic cytoplasm or intracytoplasmic mucin (mucin-producing carcinoma in situ). It also consisted, in part, of plump spindle cells with scant cytoplasm that contained argyrophilic granules in a trabecular pattern or an arrangement of perivascular pseudorosettes (atypical carcinoid tumor like-features). Mucous lake and tumor cells floating in mucin were seen in the invasive lesion (mucinous carcinoma). Immunohistochemical staining revealed endocrine differentiation of the tumor cells of both intraductal and invasive lesions. These findings suggest that the different histological features derived from pluripotent cells upon endocrine differentiation, and that endocrine differentiation of the tumor cells had already occurred at an earlier stage of carcinogenesis, prior to the appearance of the mucinous carcinoma. Cytologically, plasmacytoid tumor cells appeared in loosely cohesive clusters or as sparsely single cells in a background of a mucinous substance.

Tissue microarray analysis of neuroendocrine differentiation and its prognostic significance in breast cancer

The aim of this study was to detect neuroendocrine differentiation (NE), to determine its association with major clinicopathological parameters of breast cancer, and to study the prognostic significance of NE differentiation in a group of breast carcinomas by using tissue microarray (TMA) methodology. NE differentiation was studied by using 3 markers, synaptophysin (Syn), chromogranin A (ChA), and neuron-specific enolase (NSE) in a group of 334 patients with breast carcinoma. TMA blocks were made by using duplicate 0.6-mm-diameter tissue cores from each paraffin block. Results of immunostaining were scored on a 4-point scale, that is, as negative, weak, intermediate, and strong immunoreactivity. Positive staining of breast cancers for any of the 3 NE markers was detected in 19.5% of cases. Expression of a single marker was present in 16.2% of cases, and expression of 2 or 3 markers in combination was detected in 3.3% of cases. There was no statistically significant correlation of NE phenotype with tumor morphology, except mucinous carcinoma (3 of 6 cases positive), estrogen receptor, progesterone receptor, or nodal status. A weak correlation was noted between synaptophysin staining and higher tumor grade (P = 0.029). Analysis of disease-specific and overall survival based on up to 20 years of follow-up data showed a correlation between NSE expression and improved disease-specific (P = 0.043) and overall survival (P = 0.03) in univariate but not in multivariate analysis. The expression of Syn and ChA, as well as coexpression of multiple NE markers, had no prognostic significance.

Mucocele-like tumor of the breast caused by ductal carcinoma in situ: a case report

A mucocele-like tumor (MLT) of the breast caused by clinging and micropapillary carcinoma in situ is reported. The tumor was a smooth-contoured mass located near the nipple in the lower inner quadrant of the left breast. Ultrasonography showed a cystic tumor and distended ducts. An aspiration specimen contained abundant mucinous material and a small amount of epithelial cell components, but was insufficient for cytological diagnosis. An excisional biopsy specimen disclosed multiple cysts containing mucin with extravasation into the stroma. Additional pathologic diagnosis using consecutive microscopic sections demonstrated ductal carcinoma in situ. Subcutaneous mastectomy was subsequently performed. Histopathologic findings in the resected and biopsy specimens indicated a diagnosis of MLT caused by widely spreading clinging and micropapillary ductal carcinoma in situ. The ductal epithelium of the MLT in an open biopsy specimen must be carefully examined using consecutive microscopic sections to detect occult DCIS.

Histochemical and immunohistochemical characterization of canine mammary mucinous carcinoma

Mucinous carcinoma is a rare mammary tumour, characterized by intracellular and extracellular mucin. It is still uncertain whether the origin of the mucin is epithelial, myoepithelial or fibroblastic. Eleven canine cases originally classified as mucinous carcinomas were reassessed and compared with myoepithelial nests of mixed tumours. All samples were examined (1) histochemically by the periodic acid-Schiff (PAS) and PAS-diastase methods, and with alcian blue (pH 2.5 and pH 1.0), mucicarmine and Grimelius silver stain, and (2) immunohistochemically for cytokeratin 19, vimentin, alpha-actin and chromogranin A. This examination revealed that only five of the 11 tumours were genuine mucinous carcinomas. In these five tumours the mucus-secreting cells showed cytoplasmic cytokeratin 19 positivity; the mucus showed PAS-diastase and mucicarmine positivity, and alcianophilia which was stronger at pH 2.5 than at 1.0. The remaining six cases were re-classified as mixed tumours because both mucus and mucus-producing cells shared the following similarities with myoepithelial nests of mixed tumours: vimentin and alpha-actin cytoplasmic positivity, PAS negativity, alcianophilia both at pH 2.5 and 1.0, and mucicarmine positivity.

Fine-needle aspiration cytology findings of an uncommon micropapillary variant of pure mucinous carcinoma of the breast: review of patients over an 8-year period

BACKGROUND

Previous attempts at subclassifying pure mucinous carcinomas of the breast based on architectural patterns and other associated features are on record. A distinctive micropapillary variant with most tumor cells arranged in micropapillae/pseudoacini has not been described previously.

METHODS

The author reviewed the histologic slides from all 556 patients who underwent wide excision/mastectomy for mammary ductal carcinoma, either in situ or invasive, at Pamela Youde Nethersole Eastern Hospital, Hong Kong, during an 8-year period from early 1994 to the end of 2001. Five patients with pure mucinous carcinoma with diffuse micropapillary architecture were noted. The cytologic features (if available) were correlated with clinical, radiologic, and pathologic findings.

RESULTS

Among the five patients with pure mammary mucinous carcinoma (micropapillary variant), three patients underwent preoperative fine-needle aspiration biopsies and had specimens available for review. The direct smears and cytospin preparations were of moderate cellularity and showed cohesive clusters and micropapillae of mildly pleomorphic tumor cells among a mucoid background. True tumor papillae with fibrovascular cores were not present. Nuclear hobnailing was observed commonly, and occasional psammoma bodies were found. There were also scanty isolated tumor cells scattered around. The pseudoacinar pattern was appreciated more readily in the cell block sections. Histologic examination of the surgical specimens showed features of pure mucinous carcinoma with diffuse micropapillary architecture. The micropapillary arrangement was confirmed further by the demonstration of a reverse polarity immunostaining pattern for epithelial membrane antigen and the identification of microvilli rimming the periphery of tumor cell clusters under the electron microscope. Peritumoral lymphovascular permeation and ipsilateral axillary lymph node metastasis was found in one of the patients.

CONCLUSIONS

The micropapillary variant of mammary mucinous carcinoma demonstrates characteristic cytologic and histologic features that warrant special attention. It may represent the mucinous counterpart of invasive micropapillary carcinoma. Further analysis of a larger series of patients, however, will be required to delineate its prognostic significance, especially its propensity for lymph node metastasis.

Mucinous carcinoma of the breast with neuroendocrine differentiation

A case of mucinous carcinoma of the breast with neuroendocrine differentiation in an 89-year-old woman is presented. The patient presented with a rapidly growing right breast mass, which she had had for 2-3 years. The tumor, 15 x 8 x 5 cm, was located mainly in the upper outer quadrant. Light microscopy revealed a pure mucinous carcinoma of type B. Neuroendocrine differentiation was demonstrated by Grimelius stain and chromogranin A, as well as the presence of neurosecretory granules. The breast cancer cells were of luminal origin and had dedifferentiated to attain neuroendocrine properties.