Kei Kushitani

Immunohistochemical marker panels for distinguishing between epithelioid mesothelioma and lung adenocarcinoma

The distinction between epithelioid mesothelioma and lung adenocarcinoma remains an important diagnostic challenge for surgical pathologists. The aim of the present study was to select a limited and appropriate panel of antibodies that can differentiate between epithelioid mesothelioma and lung adenocarcinoma. Specimens of 90 epithelioid mesotheliomas and 51 lung adenocarcinomas obtained from Japanese cases were examined using calretinin, WT1, AE1/AE3, CAM5.2, cytokeratin (CK) 5/6, vimentin, epithelial membrane antigen (EMA), thrombomodulin, CEA, CA19‐9, and CA125. Ninety‐six percent of epithelioid mesotheliomas were positive for calretinin; 99% for WT1; 100% for AE1/AE; 97% for CAM5.2; 70% for CK 5/6; 91% for vimentin; 96% for EMA; 71% for thrombomodulin; 77% for mesothelin; 7% for CEA; 17% for CA19‐9; and 85% for CA125. In contrast, 33% of lung adenocarcinomas were positive for calretinin; 16% for WT1; 100% for AE1/AE3, CAM5.2, and EMA; 41% for CK 5/6; 47% for vimentin; 20% for thrombomodulin; 69% for mesothelin; 98% for CEA; 73% for CA19‐9; and 80% for CA125. For distinguishing between epithelioid mesothelioma and lung adenocarcinoma, the combination of CEA, calretinin and each WT1 or thrombomodulin was suggested to be the best panel of immunohistochemical markers.

Differential diagnosis of sarcomatoid mesothelioma from true sarcoma and sarcomatoid carcinoma using immunohistochemistry

Differentiation of sarcomatoid mesothelioma from other sarcomatoid tumors involving the pleura and other structures by light microscopy remains an important diagnostic challenge for surgical pathologists. The purpose of the present study was to investigate the utility of diagnostic immunohistochemistry for differentiating sarcomatoid mesothelioma from its histological mimics: true sarcoma and pulmonary sarcomatoid carcinoma. A total of 39 specimens of mesotheliomas with sarcomatoid components, 43 specimens of true sarcomas, and nine specimens of pulmonary sarcomatoid carcinomas were obtained from Japanese patients and examined using a 10‐antibody panel (calretinin, WT1, AE1/AE3, CAM5.2, epithelial membrane antigen, desmin, α‐smooth muscle actin, S‐100 protein, CD34, and CD68). CAM5.2 had the highest sensitivity and specificity for differentiating sarcomatoid mesothelioma from true sarcoma. The combination of CAM5.2, WT1, and AE1/AE3 is recommended for routine pathological diagnosis. Accurate clinical information is necessary for differentiating sarcomatoid mesothelioma from sarcomatoid carcinoma.

The prognostic role of pathologic invasive component size, excluding lepidic growth, in stage I lung adenocarcinoma

OBJECTIVES We performed an investigation of the prognostic significance of the invasive component size, excluding lepidic growth, in lung adenocarcinoma patients. METHODS The data from 603 patients with completely resected pathologic stage I lung adenocarcinomas were analyzed retrospectively to determine the relationship between pathologic tumor size and surgical results. RESULTS The median tumor size of the total growth and the invasive component were 2.2 cm and 1.3 cm, respectively. There were significant differences in recurrence-free survival between patients classified on the basis of invasive component sizes (≤ 0.5 cm vs 0.5-2.0 cm, P < .001; and 0.5-2.0 cm vs > 2.0 cm; P = .026). A multivariate Cox regression analysis showed that invasive component size (P = .002), age, sex, and lymphatic invasion were independent prognostic factors for recurrence-free survival, whereas total tumor size was not (P = .068). There were no significant differences in recurrence-free survival between patients who received adjuvant chemotherapy and those who did not in the group with invasive component size of 0.5 cm or less (P = .29) and in the group with invasive component size of 0.5 to 2.0 cm (P = .50). However, the recurrence-free survival of patients who received adjuvant chemotherapy was significantly better than that of those who did not in the group with invasive component size greater than 2.0 cm (P = .009). CONCLUSIONS Pathologic invasive component size, as opposed to total tumor size, is associated more significantly with malignant behavior and prognosis and specifically should be considered before choosing candidates for adjuvant chemotherapy in pathologic stage I lung adenocarcinoma.

Value of immunohistochemistry in the differential diagnosis of pleural sarcomatoid mesothelioma from lung sarcomatoid carcinoma

Aims:  The differential diagnosis of pleural sarcomatoid mesothelioma (SM) from lung sarcomatoid carcinoma (LSC) invading parietal pleura and chest wall is a challenging issue. The aim of this study was to identify useful antibodies that can be used for the differential diagnosis of pleural SM from LSC.

A Useful Antibody Panel for Differential Diagnosis Between Peritoneal Mesothelioma and Ovarian Serous Carcinoma in Japanese Cases

Malignant mesothelioma is increasing in incidence worldwide, including in Japan. However, the accurate pathologic diagnosis of pleural or peritoneal mesothelioma (PM) is sometimes difficult if adequate histologic and immunohistochemical analyses are not undertaken. The aim of this study was to identify a useful antibody panel for distinguishing PM from ovarian serous papillary adenocarcinoma (SC). We obtained 29 PMs (23 epithelioid mesotheliomas and 6 biphasic mesotheliomas) and 20 SCs from our surgical pathology files. Immunohistochemical analysis was undertaken using 13 commercially available antibodies. No significant sex differences in antigen expression among the 29 PMs were observed. The results identified calretinin and thrombomodulin as positive markers and Ber-EP4, MOC-31, CA19-9, and estrogen receptor as negative markers with relatively high sensitivity and specificity for the differential diagnosis of PM and SC. The combination of these positive and negative markers may contribute to accurate diagnosis and adequate therapy for PM and ovarian SC.

Caveolin‐1 is a novel immunohistochemical marker to differentiate epithelioid mesothelioma from lung adenocarcinoma

Aims:  The incidence of mesothelioma is increasing in Europe, Japan and other developing countries. There is difficulty in the accurate diagnosis of mesothelioma and its differentiation from lung adenocarcinoma. Mesothelioma shows a complex immunohistochemical profile. Therefore, the use of a immunohistochemical panel that includes both positive and negative mesothelial markers has become a general rule for its accurate diagnosis. However, they are still not sufficient. The aim was to assess the diagnostic utility of caveolin‐1 (Cav‐1), which is expressed in endothelial cells, alveolar type I pneumocytes and mesothelial cells, as a novel positive marker of mesothelioma.

Role of lymphatic invasion in the prognosis of patients with clinical node-negative and pathologic node-positive lung adenocarcinoma

OBJECTIVE Some patients with clinical T1 N0 M0 lung adenocarcinoma have pathologic lymph node metastasis. However, neither the precise prognosis nor the factors predictive of the prognosis of such patients have yet been identified. METHODS Our study included 609 patients with clinical T1 N0 M0 lung adenocarcinoma; 568 (93.3%) pathologic node negative [pN(-)] and 41 (6.7%) pathologic node positive [pN(+)] patients, diagnosed after complete surgical resection. The association between prognosis and pathologic findings was analyzed retrospectively. RESULTS pN(+) patients had a significantly lower lepidic growth component ratio (10% vs 50%), a higher lymphatic invasion (LI) rate (68% vs 11%), vessel invasion rate (59% vs 14%), and visceral pleural invasion rate (29% vs 9%), compared with pN(-) patients (all Ps < .001). Surprisingly, 13 of 41 (32%) pN(+) patients showed no LI. In pN(-) patients, a multivariate analysis of recurrence-free survival revealed that lower lepidic growth component ratio, and lymphatic, vessel, and pleural invasion were significantly correlated with a poor prognosis (P = .008, .045, .031, and .024). However, in pN(+) patients, the multivariate analysis of recurrence-free survival showed that only LI was a significant independent prognostic factor (P = .037). The 5-year recurrence-free survival rates were as follows: 91.2% for pN(-)/LI(-) patients, 68.2% for pN(-)/LI(+) patients, 63.5% for pN(+)/LI(-) patients, and 41.9% for pN(+)/LI(+) patients. LI status stratified the prognosis not only in patients with no nodal metastasis but also in those with metastasis. CONCLUSIONS LI, which is not always present in node-positive adenocarcinoma, is an important prognostic variable in patients with node involvement.

Aberrant methylation and loss of expression of O6-methylguanine-DNA methyltransferase in pulmonary squamous cell carcinoma and adenocarcinoma

O6‐Methylguanine‐DNA methyltransferase (MGMT) is a DNA repair protein that protects cells against the carcinogenic effects of alkylating agents. The methylation status of the MGMT gene was investigated by methylation‐specific polymerase chain reaction (PCR) and expression status was investigated by immunohistochemistry in 70 cases of pulmonary squamous cell carcinoma (pulmonary SqCC), including 23 cases of the central type and 47 cases of the peripheral type, and in 53 cases of the peripheral type of pulmonary adenocarcinoma (AC). The frequency of MGMT methylation was 36% in SqCC and 42% in AC. Cases with MGMT methylation correlated significantly with T factor in SqCC (P = 0.047) and AC (P = 0.03). In SqCC, the frequency of MGMT methylation was 26% in the central type and 40% in the peripheral type; a significant correlation was not found (P = 0.29). In AC with mixed subtypes showing MGMT methylation, the level of MGMT expression in the bronchioloalveolar carcinoma (BAC) area (non‐invasive status) was significantly higher than that in the papillary or acinar AC area (invasive status; P = 0.0002). This trend was not found in AC with mixed subtypes showing no MGMT methylation (P = 0.10). These findings suggest that MGMT inactivation is an event that occurs in the late carcinogenic process in SqCC and AC, and that AC progress from non‐invasive status to invasive status with MGMT inactivation induced by the promoter DNA methylation.

Overexpression of CD26/DPPIV in mesothelioma tissue and mesothelioma cell lines

Mesothelioma, a highly aggressive cancer with poor prognosis and refractory to currently available therapies show increasing trends of its incidence in Japan and other developing countries. Although surgery is a gold standard for patients with early mesothelioma, most patients with advanced disease are not suitable for surgical resection and have option of palliative chemotherapy alone. One of the new treatment strategies for mesothelioma, the humanized anti-CD26 monoclonal antibody therapy is under development. CD26, a 110-kDa transmembrane glycoprotein with known dipeptidyl peptidase IV activity, plays a role in tumor development and its expression was reported in various human malignancies. This study determined the preliminary selection criteria for humanized monoclonal anti-CD26 antibody therapy. Eighty-one epithelioid (49 differentiated and 32 less differentiated), 34 sarcomatoid, 19 biphasic mesothelioma and 8 mesothelioma cell lines were immunohistochemically examined using 8 different commercially available anti-CD26 antibodies for membranous and cytoplasmic expression. The cytoplasmic expression of CD26 was observed in all histological types of mesothelioma, while the membranous expression of CD26 was found in 88% of differentiated and 69% of less differentiated epithelioid mesothelioma, and none of sarcomatoid mesothelioma with anti-CD26 antibodies with rabbit polyclonal anti-DPP4 antibody and similar results were also obtained with goat polyclonal anti-DPP4/CD26 antibody. These antibodies absorbed with soluble human CD26 proteins do not show CD26 expression in mesothelioma tissue, suggesting these two antibodies localize true CD26 protein. Seven mesothelioma cell lines, including sarcomatoid types, also showed membranous expression of CD26 in cellblock preparation. CD26 vector transfection to CD26-negative MSTO-211H cells showed membranous expression of CD26 by flow cytometry, but not in tumor developed in NOD/SCID mice with inoculation of CD26 vector transfected MSTO-211H cells. We found that both rabbit and goat polyclonal antibodies are suitable for immunohistochemical evaluation of membranous expression of CD26 in mesothelioma.

Prediction for prognosis of resected pT1a-1bN0M0 adenocarcinoma based on tumor size and histological status: relationship of TNM and IASLC/ATS/ERS classifications.

OBJECTIVES This study aimed to estimate the relationship between 7th TNM classification and IASLC/ATS/ERS classification with regard to tumor size and pathological status and to determine the utility of these classifications for predicting prognosis in resected node-negative adenocarcinoma with tumor size ≤2.0 cm and >2.0-3.0 cm. MATERIALS AND METHODS We reviewed 321 pN0M0 lung adenocarcinoma cases resected at Hiroshima University Hospital from January 1991 to December 2010. Histological differences between T1a and T1b based on the IASLC/ATS/ERS classification were estimated and followed by evaluation of overall survival (OS) and recurrence-free interval (RFI) based on differences in tumor size and histological features. RESULTS We found 188 cases of pT1a-1bN0M0 (135 T1a, 53 T1b). Pathological T1a tumors included significantly more adenocarcinoma in situ (AIS) cases and minimally invasive adenocarcinoma (MIA) cases than T1b tumors (60.7% vs 18.8%, respectively; p<0.0001), while more invasive adenocarcinoma cases were included in pT1b. By considering the two classifications simultaneously, the 5-year OS rates of T1a AIS/MIA, T1b AIS/MIA, T1a invasive adenocarcinoma, and T1b invasive adenocarcinoma were 97.5%, 87.5%, 95.8%, and 86.8%, respectively. The 5-year RFIs of T1a AIS/MIA, T1b AIS/MIA, T1a invasive adenocarcinoma, and T1b invasive adenocarcinoma were 100%, 100%, 91.3%, and 72.5%, respectively. T1a AIS/MIA and T1b AIS/MIA could be separated as good prognostic cases with a 100% RFI. Multivariate analysis indicated that only T1b invasive adenocarcinoma was an independent factor for predicting recurrence (p=0.001). CONCLUSION Compared to a single classification, combining TNM and IASLC/ATS/ERS classifications could provide more detail information concerning disease recurrence. AIS and MIA should be handled equally, regardless of tumor size, because their non-/less invasive status is more useful for predicting prognosis than their tumor size classification. In contrast, the T descriptors based on TNM classification are important for predicting prognosis in invasive adenocarcinoma.