Mucinous Balls Tangled With Mesothelial Cells and MUC2-Positive Cancer Cells in the Ascites of Pseudomyxoma Peritonei.

Pseudomyxoma peritonei (PMP) is characterized by extensive mucinous ascites following rupture of mucinous neoplasms of an intra-abdominal origin, and contain secreted gel-forming mucins such as MUC2 and MUC5AC. We encountered a 66-year-old Japanese man complaining of abdominal distension. Ascites at the site was gelatinous upon gross examination, and needle aspirate smears showed histiocytes and many mucinous balls wrapped in spindle cells, which were positive for vimentin, pan-cytokeratin, and podoplanin. The cell block showed several adenocarcinoma clusters, which were positive for MUC2, MUC5AC, CK20, and CDX-2, and negative for CK7. From these findings, a diagnosis of PMP arising from colon cancer was indicated. Cytoreductive surgery was performed, and the cystic diverticulum was found to be infiltrated by tumor cells in the sigmoid colon that caused PMP. Mucinous balls surrounded by mesothelial cells and MUC2-positive adenocarcinoma cells are useful clues in the diagnosis of PMP. Diagn. Cytopathol. 2016;44:628-631. © 2016 Wiley Periodicals, Inc.

Fine-needle aspiration cytology of triple-negative basal-like breast cancer.

Invasive breast cancer is divided into luminal A, luminal B, HER2 overexpression, basal-like (BL) and normal-like subtypes, among which the BL subtype has the worst prognosis. The purpose of this study was to determine the clinicopathological and cytological characteristics of BL breast cancer (BLBC). Fine-needle aspiration cytology samples from 17 patients with consecutive BLBC were investigated, and the findings were compared with those of other subtypes (10 cases each) for the following cytomorphological features: necrosis; lymphocyte infiltration; mitotic index; apoptosis; naked nuclei; nuclear/cytoplasmic ratio; nuclear margin, size and pleomorphism; chromatin granularity and density; and nucleolar appearance. Histologically, the BLBCs were heterogeneous, and included medullary carcinoma and metaplastic carcinoma, in addition to invasive ductal carcinoma. Cytologically, high mitotic index, naked nuclei, and irregular nuclear margin were significantly observed when compared with both the luminal A and B subtypes. Large nuclei with nucleoli and lymphocyte infiltration were frequently seen compared with the luminal A and B subtypes, respectively. Squamous nodules were seen in all metaplastic cases, but not in the HER2 overexpression subtype. Lymphocyte infiltration, squamous metaplasia, and nuclear findings such as a high mitotic index, naked or large nuclei, an irregular nuclear margin and the presence of nucleoli, may be clues indicating BLBC.

Detection of human epidermal growth factor receptor 2 protein and gene in fine needle aspiration cytology specimens and tissue sections from invasive breast cancer: can cytology specimens take the place of tissue sections?

Overexpression of HER2 protein and HER2 gene amplification in breast cancer are prognostic factors for the response to specific medical treatments such as trastuzumab, endocrine therapy, and chemotherapy. Whereas HER2 expression and gene amplification are generally examined in tissue sections, we investigated whether specimens from fine needle aspiration cytology (FNAC) are adequate for these analyses. HER2 protein overexpression and HER2 gene amplification were assessed in both FNAC specimens and tissue sections from 58 cases of invasive breast cancer. Immunohistochemistry assay for HER2 protein expression was performed according to the HercepTest protocol, and HER2 gene amplification was examined with the Spot-light CISH (chromogenic in situ hybridization) Detection kit. There was a significant positive correlation between assessments of HER2 protein status in the cytology specimens and tissue sections. The sensitivity, specificity, and accuracy of HER2 gene amplification detection in cytology specimens in relation to those in tissue sections were 84.0% (21/25 cases), 87.9% (29/33 cases), and 86.2% (50/58 cases), respectively. FNAC specimens are suitable for detection of HER2 overexpression and HER2 gene amplification in invasive breast cancer.

Interlaboratory comparison in HercepTest assessment of HER2 protein status in invasive breast carcinoma fixed with various formalin-based fixatives.

Although formalin-based fixatives are used in pathologic laboratories, there is no strictly standardized fixation protocol in Japan. To examine interlaboratory variation caused by different conditions of fixation in the assessment of human epidermal growth factor receptor (HER) 2 status on pathologic tissues, 274 archival invasive breast carcinomas from 5 different laboratories were evaluated using the HercepTest. In 1 laboratory in which 10% neutral buffered formalin was used, as recommended by the manufacturer, the overexpression rate was 22.4% and fell within the statistical expected range (20%-30%) for HER2 overexpression in breast carcinomas. The overexpression rates in the other 4 laboratories, in which either 20% nonbuffered formalin or 15% neutral buffered formalin was used, were near the expected range for HER2 overexpression. To clarify the influence of prolonged formalin fixation on the HercepTest, we compared 1-day with 7-day fixations using 36 cases fixed with 20% nonbuffered formalin. Of the 36 cases, 7 showed 3+ staining with 1-day fixation and sustained the same scoring results with 7-day fixation, although the staining intensities in these cases were reduced with the prolonged fixation. These results indicated that the immunohistochemical assessment of HER2 status with the HercepTest was comparatively resistant to prolonged fixation conditions and provided stable staining results in positive cases, particularly 3+ patients.