BAP1 Loss by Immunohistochemistry Predicts Improved Survival to First-Line Platinum and Pemetrexed Chemotherapy for Patients With Pleural Mesothelioma: A Validation Study.

INTRODUCTION: Pleural mesothelioma (PM) is an aggressive malignancy with no identified predictive biomarkers. We assessed whether tumor BAP1 status is a predictive biomarker for survival in patients receiving first-line combination platinum and pemetrexed therapy. METHODS: PM cases (n = 114) from Aalborg, Denmark, were stained for BAP1 on tissue microarrays. Demographic, clinical, and survival data were extracted from registries and medical records. Surgical cases were excluded. BAP1 status was associated with overall survival (OS) by Cox regression and Kaplan-Meier methods. Results were validated in an independent cohort from Perth, Australia (n = 234). RESULTS: BAP1 loss was found in 62% and 60.3% of all Danish and Australian samples, respectively. BAP1 loss was an independent predictor of OS in multivariate analyses corrected for histological subtype, performance status, age, sex, and treatment (hazard ratio = 2.49, p < 0.001, and 1.48, p = 0.01, respectively). First-line platinum and pemetrexed-treated patients with BAP1 loss had significantly longer median survival than those with retained BAP1 in both the Danish (20.1 versus 7.3 mo, p < 0.001) and Australian cohorts (19.6 versus 11.1 mo, p < 0.01). Survival in patients with BAP1 retained and treated with platinum and pemetrexed was similar as in those with best supportive care. There was a higher OS in patients with best supportive care with BAP1 loss, but it was significant only in the Australian cohort (16.8 versus 8.3 mo, p < 0.01). CONCLUSIONS: BAP1 is a predictive biomarker for survival after first-line combination platinum and pemetrexed chemotherapy and a potential prognostic marker in PM. BAP1 in tumor is a promising clinical tool for treatment stratification.

Analysis of early pleural fluid samples in patients with mesothelioma: A case series exploration of morphology, BAP1, and CDKN2A status with implications for the concept of mesothelioma in situ in cytology.

BACKGROUND: The concept of mesothelioma in situ has been revisited and is a new World Health Organization diagnostic entity. The definition centers on ancillary techniques used in pleural mesothelioma (PM) assessment. At the authors' institution, most PM diagnoses are made on cytologic specimens. Effusion samples obtained before definitive PM diagnosis were interrogated using BRCA1-associated protein 1 gene (BAP1), cyclin-dependent kinase inhibitor 2A gene (CDKN2A) and cytologic evaluation to assess whether early or possible in situ disease could be characterized. METHODS: All cases of PM diagnosed between January 2008 and December 2019 were identified at a tertiary referral center. Patients who had a pleural fluid sample collected 24 months before the diagnosis were selected, numbering 8 in total. The cytomorphology of each sample was reviewed; and, retrospectively, BAP1 immunohistochemistry (IHC) and CDKN2A fluorescence in situ hybridization (FISH) were performed on initial and diagnostic samples. RESULTS: The initial samples were deemed benign in 5 cases and atypical mesothelial proliferations in 3 cases. A spectrum of apparently normal to atypical cytomorphologic changes was identified. BAP1 loss was present in 6 of 8 initial cases, whereas CDKN2A homozygous deletion was identified in 1 of 7 initial cases. Either abnormality was identified in 7 of 8 initial samples. CONCLUSIONS: Detectable abnormalities of BAP1 IHC and CDKN2A FISH were present in pleural fluid specimens before the development of cytomorphologic features diagnostic of PM. This is the largest series to date describing cytology samples early in the course of PM development, thereby highlighting a possible cytological equivalent for mesothelioma in situ.

Diagnostic utility of BAP1 for malignant pleural mesothelioma in pleural fluid specimens with atypical morphology.

OBJECTIVE: To assess the utility of BRCA1-associated protein 1 (BAP1) immunohistochemistry (IHC) for the diagnosis of malignant pleural mesothelioma (MPM) in fluid samples with atypical cytology. METHODS: Pleural fluid samples with an atypical mesothelial proliferation (diagnostic categories: 'atypical' and 'suspicious') received between January 2015 and March 2018 at a tertiary referral centre were identified. Results of routine IHC testing were recorded for each case. BAP1 by IHC was performed and a final diagnosis sought from subsequent pathology specimens, medical records, or consensus clinical diagnosis. RESULTS: Of 50 cases identified, 41 were reported as atypical and 9 as suspicious. Seven (14%) demonstrated loss of BAP1 staining, 40 retained BAP1 staining, 1 had heterogeneous staining, and 2 had insufficient cells for analysis. All seven cases with BAP1 loss were diagnosed with MPM on follow-up. Of those with retained BAP1, 52.5% (21) were subsequently diagnosed with MPM, while 40% (16) had non-MPM diagnoses after a median follow-up of 24 months. Three cases were not further investigated based on patient and clinician decision. The case with heterogeneous staining was diagnosed as mesothelioma by clinical consensus. CONCLUSIONS: BAP1 IHC loss is highly specific for malignancy and has value as a rule-in test. Even in a tertiary centre with clinical interest in the cytological diagnosis of MPM this investigation was able to increase diagnostic accuracy beyond routine IHC studies. Cytological criteria remain valuable, as retained BAP1 in an atypical or suspicious mesothelial proliferation cannot exclude malignancy.

Typical and atypical carcinoid tumors of the lung: a clinicopathological correlation of 783 cases with emphasis on histological features.

We present 783 surgical resections of typical and atypical carcinoid tumors of the lung identified in the pathology files of 20 different pathology departments. All cases were critically reviewed for clinical and pathological features and further correlated with clinical outcomes. Long-term follow-up was obtained in all the patients and statistically analyzed to determine significance of the different parameters evaluated. Of the histopathological features analyzed, the presence of mitotic activity of 4 mitoses or more per 2 mm2, necrosis, lymphatic invasion, and lymph node metastasis were identified as statistically significant. Tumors measuring 3 cm or more were also identified as statistically significant and correlated with clinical outcomes. Based on our analysis, we consider that the separation of low- and intermediate-grade neuroendocrine neoplasms of the lung needs to be readjusted in terms of mitotic count as the risk of overgrading these neoplasms exceeds 10% under the current criteria. We also consider that tumor size is an important feature to be considered in the assessment of these neoplasms and together with the histological grade of the tumor offers important features that can be correlated with clinical outcomes.

Reconsideration of the first recognition of breast implant-associated anaplastic large cell lymphoma: A critical review of the literature.

The current literature credits Keech and Creech with the first report of breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) in 1997. Here we discuss what we consider is the first ever description of BIA-ALCL, a recently recognized entity by the WHO. We unearthed the description of a patient that was diagnosed with primary effusion lymphoma (PEL), surrounding a breast implant in 1996. In light of the current state of knowledge, we evaluated the evidence presented in 1996 and consider that BIA-ALCL is a more appropriate diagnosis rather than PEL. We base our proposal on the following features: 1). clinical presentation of effusion around a breast implant, 2). occurring in an HIV negative patient, 3). absence of EBV co-infection, and 4). a historically questionable demonstration of HHV8. In effect we further support that HHV8 is not related with BIA-ALCL based on the following facts: 1). An extensive review of the literature did not disclose a similar case in the next 24 years, 2). Use of state of the art HHV8 by immunohistochemistry did not disclose any positive case among 30 randomly tested cases. We believe this matter is of importance because in the current WHO, the assertion that PEL is a possible complication of breast implants may lead to a diagnosis with poor prognosis and susceptible of morbidity related with aggressive therapy, in contrast with BIA-ALCL that can be cured with surgery alone.

A proposal for pathologic processing of breast implant capsules in patients with suspected breast implant anaplastic large cell lymphoma.

Breast implant anaplastic large cell lymphoma is an entity recently recognized by the World Health Organization. The tumor arises around textured-surface breast implants and is usually confined to the surrounding fibrous capsule. Currently, there are no recommendations for handling and sampling of capsules from patients with suspected breast implant anaplastic large cell lymphoma without a grossly identifiable tumor. We analyzed complete capsulectomies without distinct gross lesions from patients with breast implant anaplastic large cell lymphoma. The gross appearance of the capsules as well as the presence, extent and depth of tumor cells on the luminal side and number of sections involved by lymphoma were determined by review of routine stains and CD30 immunohistochemistry. We then used a mathematical model that included the extent of tumor cells and number of positive sections to calculate the minimum number of sections required to identify 95% of randomly distributed lesions. We identified 50 patients with breast implant anaplastic large cell lymphoma who had complete capsulectomies. The implants were textured in all 32 (100%) cases with available information. Anaplastic large cell lymphoma was found in 44/50 (88%) capsules; no tumor was found in six (12%) patients who had lymphoma cells only in the effusion. The median number of sections reviewed was 20 (range, 2-240), the median percentage of sections involved by tumor was 6% (range, 0-90%), and the median percentage of sections involved by lymphoma was 10% (range, 0-90%). Invasion deep into or through the capsule was identified in 18/50 (36%) patients. In patients with breast implant anaplastic large cell lymphoma without a grossly identifiable tumor we identified a spectrum of involvement and we propose a protocol for handling, sampling and reporting these cases. The number of sections to exclude the presence of lymphoma with more than 95% certainty was supported by a mathematic rationale.

Thymoma: a clinicopathological correlation of 1470 cases.

We present 1470 surgical resections for thymoma identified in the pathology files of 14 institutions from 11 countries with the purpose of determining and correlating a simplified histological classification of thymoma and pathological staging with clinical outcome. The study population was composed of 720 men and 750 women between the ages of 12 and 86 years (average, 54.8 years). Clinically, 137 patients (17%) had a history of myasthenia gravis, 31 patients (3.8%) of other autoimmune disease, and 55 (6.8%) patients of another neoplastic process. Surgical resection was performed in all patients. Histologically, 1284 (87.13%) cases were thymomas (World Health Organization types A, B1, and B2, and mixed histologies), and 186 (12.7%) were atypical thymomas (World Health Organization type B3). Of the entire group, 630 (42.9%) were encapsulated thymomas, and 840 (57.9%) were invasive thymomas in different stages. Follow-up information was obtained in 1339 (91%) patients, who subsequently were analyzed by univariate and multivariate statistical analysis. Follow-up ranging from 1 to 384 months was obtained (mean, 69.2 months) showing tumor recurrence in 136 patients (10.1%), whereas 227 died: 64 (28.2%) due to tumor and 163 (71.8%) due to other causes. Statistical analysis shows that separation of these tumors into thymoma and atypical thymoma is statistically significant (P = .001), whereas tumor staging into categories of encapsulated, minimally invasive, and invasion into adjacent organs offers a meaningful clinical assessment with a P = .038. Our findings suggest that our simplified histological schema and pathological staging system are excellent predictors of clinical outcome.

A massive pleural-based desmoid tumour.

A 49-year-old Pakistani male presented with "heaviness" in his chest. Chest radiograph and computed tomography (CT) confirmed a massive left-sided pleural-based opacity. Three years ago, he was investigated for a left-sided lymphocytic, exudative pleural effusion following an episode of dengue fever. Tube thoracostomy removed 1.3 L of fluid. Pleural biopsy and bronchial washings were non-contributory. He received empirical anti-tuberculosis treatment and remained asymptomatic until this presentation. To investigate the new pleural mass, he underwent a video-assisted thoracoscopic surgery, which revealed a 2.2 kg mass in the pleural cavity involving the anterior mediastinum and chest wall and adhered to the visceral pleura. Following conversion to an open thoracotomy, the mass was completely excised, which involved non-anatomical lung resection. Histopathology and immunohistochemistry of the resected tumour were consistent for a desmoid tumour. He was followed up for 9 months with no evidence of tumour recurrence. Predominantly pleural-based desmoid tumour is rare but should be included in the differential diagnosis of spindle cell tumours.

Histopathology of removed indwelling pleural catheters from patients with malignant pleural diseases.

BACKGROUND AND OBJECTIVE: Indwelling pleural catheters (IPC), used for management of malignant pleural effusions, are often left in situ for a long duration. This study reports for the first time the histological findings of IPCs removed from patients with underlying pleural malignancy. METHODS: Forty-one IPCs (in situ for median 126 days, interquartile range 43-226) that were removed over a 54-month period from a single centre were examined. RESULTS: Mesothelioma (n = 18) was the predominant underlying malignancy followed by breast, tubo-ovarian and lung carcinomas. The catheter tubing was fully intact macroscopically in all IPCs. There was no evidence of direct tumour invasion or cancer cell growth on the catheter surfaces in none of the 29 IPCs that were histologically examined. Malignant cells were seen within organizing fibrinous tissues in the lumen of 11 IPCs (27%). A foreign body giant cell reaction was present at the cuff site in all the 29 IPC in which the subcutaneous cuff was examined. Acute (n = 10) and/or chronic inflammatory changes were seen in the luminal contents in all 41 IPCs. CONCLUSION: Our study provides reassuring evidence that the IPC material does not support direct tumour growth or invasion even in the setting of high mesothelioma prevalence. See Editorial, page 787.

Pleuroscopic cryoprobe biopsies of the pleura: a feasibility and safety study.

BACKGROUND AND OBJECTIVE: Flexi-rigid pleuroscopy is a useful tool in the work-up of pleural effusions, but pleural biopsy using flexible forceps can be difficult in some patients. This study evaluated the feasibility, safety and diagnostic value of using a flexible cryoprobe to obtain parietal pleural biopsies during pleuroscopy. METHODS: This was a single-centre retrospective study. In patients undergoing diagnostic pleuroscopy, pleural biopsy using flexible forceps, followed by a flexible cryoprobe introduced through the pleuroscope, were performed. A pathologist independently reviewed all biopsies. Any complications, particularly bleeding, were recorded. All patients were followed up for ≥ 6 months (median 12 months (range 7-26)). RESULTS: Twenty-two patients (21 males; median age 72 years; 14 right-sided effusions) were included. All underwent flexible forceps biopsies (FFB) and cryoprobe biopsies (CB) of pleura. FFB and CB established a definitive diagnosis in 20/22 (90%). CB successfully obtained pleural tissue suitable for histopathological analysis in all patients. CB was larger than FFB (median, 25-75 IQR of 10, 7-15.8mm vs 4, 3-8mm), and had better preserved cellular architecture and tissue integrity. Crush artefacts were less common with CB (2/22) compared with FFB (21/22). No significant bleeding was reported. CONCLUSIONS: CB during flexi-rigid pleuroscopy is feasible, safe and effective. Its routine use during flexi-rigid pleuroscopy requires further evaluation.

Anaplastic large-cell lymphoma associated with breast implants: a unique entity within the spectrum of peri-implant effusions.

Anaplastic large-cell lymphoma (ALCL) is a rare and newly described complication associated with breast implants. Patients often present with a peri-implant effusion, which is amenable to fine-needle aspiration. The laboratory handling of peri-implant effusions for cytology and ancillary studies is as crucial as recognizing the characteristic cytology of ALCL. All cases of peri-implant effusions were retrieved from the PathWest database between January 2003 and May 2013, yielding four cases of breast implant-associated ALCL and six benign samples. The cytological features were evaluated and information from ancillary studies collated. Clinical and follow-up histology was available in all cases. All ALCL cases contained highly atypical lymphoid cells including 'hallmark' cells. In contrast, benign peri-implant effusions showed a mixture of inflammatory cells, being either neutrophil-rich (three cases) or lymphocyte-rich (three cases). A CD30 positive, ALK1 negative immunophenotype was demonstrated in all cases on cell block immunohistochemistry. Flow cytometry and T-cell receptor clonality studies confirmed aberrant T-cell immunophenotype in four of four and clonally rearranged T-cell receptor antigens in three of three cases. ALCL was identified in three of four subsequent capsulectomies. Staging confirmed disease limited to the capsular tissue or peri-implant effusion in all cases. None of the six patients with benign peri-implant effusions developed lymphoma during follow-up. Cases of ALCL accounted for 40% of peri-implant effusions received over a 10-year period, indicating the rarity of these samples and the high likelihood of malignancy. Awareness of this entity and its presentation should allow for appropriate triage of these specimens and definitive diagnosis on effusion specimens.

Optimizing the multimodal approach to pancreatic cyst fluid diagnosis: developing a volume-based triage protocol.

BACKGROUND: The objective of this study was to develop a triage algorithm to optimize diagnostic yield from cytology, carcinoembryonic antigen (CEA), and v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) testing on different components of a single pancreatic cyst fluid specimen. The authors also sought to determine whether cell block supernatant was suitable for CEA and KRAS testing. METHODS: Fifty-four pancreatic cysts were triaged according to a volume-dependent protocol to generate fluid (neat and supernatant) and cell block specimens for cytology, comparative CEA, and KRAS testing. Follow-up histology, diagnostic cytology, or a combined clinicopathologic interpretation was recorded as the final diagnosis. RESULTS: There were 26 mucinous cystic lesions and 28 nonmucinous cystic lesions with volumes ranging from 0.3 mL to 55 mL. Testing different components of the specimens (cell block, neat, and/or supernatant) enabled all laboratory investigations to be performed on 50 of 54 cyst fluids (92.6%). Interpretive concordance was observed in 17 of 17 cases (100%) and in 35 of 40 cases (87.5%) that had multiple components tested for CEA and KRAS mutations, respectively. An elevated CEA level (>192 ng/mL) was the most sensitive test for the detection of a mucinous cystic lesion (62.5%) versus KRAS mutation (56%) and "positive" cytology (61.5%). KRAS mutations were identified in 2 of 25 mucinous cystic lesions (8%) in which cytology and CEA levels were not contributory. CONCLUSIONS: A volume-based protocol using different components of the specimen was able to optimize diagnostic yield in pancreatic cyst fluids. KRAS mutation testing increased diagnostic yield when combined with cytology and CEA analysis. The current results demonstrated that supernatant is comparable to neat fluid and cell block material for CEA and KRAS testing.

Diagnosis of necrotic and degenerate thyroid lesions: value of immunohistochemistry.

AIMS: Classification of necrotic or degenerate thyroid nodules can be difficult. The aim of this study was to investigate the value of cytokeratins, thyroid-specific markers (TTF-1 and thyroglobulin) and HBME-1 antibodies in such thyroid lesions. METHODS AND RESULTS: Twenty-eight necrotic or degenerate thyroid lesions, including four cervical cystic papillary carcinoma (CPC) metastases, were evaluated with immunohistochemistry for TTF-1, thyroglobulin, HBME-1, AE1&3, Cam5.2, MNF116 and cytokeratin (CK)19. There was loss of TTF-1 staining in all necrotic lesions, with positive staining in degenerate tumour cells of all four metastatic CPCs. Thyroglobulin was retained in 18 lesions. Dual CK19 and HBME-1 expression was seen only in six of seven necrotic papillary thyroid carcinomas and the four metastatic CPCs. Retained immunoreactivity for AE1&3 and Cam5.2 was seen in most necrotic papillary carcinomas (n = 11/11 and n = 10/11, respectively), poorly differentiated carcinomas (n = 2/3 and n = 3/3, respectively) and follicular-patterned areas of anaplastic carcinoma (n = 3/5 and n = 4/5, respectively). Cam5.2 showed spurious staining of macrophages in eight lesions. CONCLUSIONS: Thyroglobulin is useful in establishing the thyroid origin of a necrotic lesion. TTF-1 may be useful for highlighting degenerate tumour cells within metastatic CPCs. Retained expression of CK19 and HBME-1 is seen in necrotic papillary carcinomas. AE1&3 is the most specific and Cam5.2 the most sensitive of the CK cocktails in non-viable thyroid lesions.

Screening for defective DNA mismatch repair in stage II and III colorectal cancer patients.

BACKGROUND & AIMS: Colorectal cancers associated with the hereditary nonpolyposis colorectal cancer (HNPCC) syndrome usually present in younger patients, show loss of mismatch repair (MMR) gene expression, and exhibit microsatellite instability (MSI). About 12% of sporadic colorectal cancers also show MMR loss and MSI. The aims of this study were to evaluate MMR loss and MSI in relation to patient age, sex, tumor stage, and site in the large bowel. METHODS: Tissue microarrays were created from 1020 stage II and III colorectal cancer cases and immunohistochemical staining performed to detect expression of the 2 major MMR proteins, hMLH1 and hMSH2. MSI was determined using the BAT-26 mononucleotide repeat. RESULTS: Ten percent of tumors showed loss of hMLH1 expression and 1.2% showed loss of hMSH2 expression. hMLH1 loss was more frequent in women (P < .001), older patients (P = .004), earlier stage tumors (P = .0001), and proximal colon tumors ( P < .0001). In contrast, tumors showing hMSH2 loss were more frequent in younger (P < .001), male (P = .05) patients and were distributed evenly between the proximal colon and distal colon/rectum. Eleven percent of tumors were MSI+ and these showed similar age, sex, stage, and site characteristics as tumors with hMLH1 loss. Discordance between MMR loss and MSI+ was found in 24 of 983 (2.4%) tumors. Of the 231 patients aged <60 years at diagnosis, 12 (5.2%) showed loss of hMLH1 and 8 (3.5%) showed loss of hMSH2. CONCLUSIONS: Routine immunohistochemical screening for MMR loss in younger colorectal cancer patients may provide a useful, first-step screening tool for the population-based detection of HNPCC.