The utilization and utility of immunostains in body fluid cytology

Optimal Volume Assessment for Serous Fluid Cytology

OBJECTIVE

This study aimed to investigate the optimal volume of serous fluid needed for accurate diagnosis using The International System for Reporting Serous Fluid Cytopathology (TIS), as well as to provide information on the distribution of serous effusion cases in the TIS categories (ND: non-diagnostic, NFM: negative for malignancy, AUS: atypia of undetermined significance, SFM: suspicious for malignancy, MAL: malignant) and relevant epidemiological data.

METHODS

A retrospective analysis of 2340 serous effusion cases (pleural, peritoneal, and pericardial) from two hospitals between 2018 and 2020 was conducted. TIS categories were assigned to each case, and for 1181 cases, these were correlated with the volume of the analyzed fluid.

RESULTS

Our study found statistically significant differences in volume distributions between certain TIS categories. Statistically lower volumes were observed in NFM compared to MAL, in UNCERTAIN (ND, AUS, SFM) compared to both MAL and NFM, and in NOT MAL (ND, NFM, AUS, SFM) compared to MAL. However, these differences were not substantial enough to hold any clinical relevance.

CONCLUSIONS

This study suggests that while fluid volume may slightly influence the TIS category, it does not impact the diagnostic accuracy of serous effusion cytology. Therefore, the ideal serous effusion specimen volume can be defined solely by practical parameters.

Immunohistochemistry and immunofluorescence utilization audit by subspecialty in an academic setting: A step toward stewardship

There are immunohistochemistry (IHC) and immunofluorescence (IF) panels described in the literature and established by personal and institutional experiences that are in common use by pathologists in their daily practice. Stewardship is a difficult discussion because IHC utilization is influenced by many factors including the pathologist's experience, background, practice setting, personal bias, and medicolegal culture. We developed the methodology to audit the IHC/IF utilization in our academic subspecialty practice. We aim to share this methodology and to provide our data that can be used for consideration by other subspecialized academic practices. This analysis included a total of 63,157 specimens that were accessioned during 2022, representing 38,612 cases. The likelihood of ordering IHC/IF ranged from 1 % (in genitourinary pathology) to 59 % (in renal pathology). The average percentage of specimens with IHC/IF was 21 % for the entire practice. In cases where IHC/IF was ordered, the number of stained slides averaged 4.9 per specimen for the entire practice. The number of IHC/IF slides per specimen ranged from 1.9 (in gastrointestinal pathology) to 12.2 (in renal pathology). The highest number of antibodies ordered for a single specimen by subspecialty ranged from 11 (in cardiac pathology) to 63 (in dermatopathology). Renal pathology was the only subspecialty that had an average number of IHC/IF slides that was statistically significantly different from all other subspecialties. We described the various patterns of utilization by subspecialty and rationalized their subtle differences. We also analyzed the types of cases that exceeded the reimbursement limits set by the Centers for Medicare and Medicaid Services (CMS).

Diagnostic Utility of Claudin4 and Comparison with BerEp4 as a Marker for Metastatic Adenocarcinoma in Serous Effusions

INTRODUCTION

Fluid cytology for malignant cells is important for diagnosis and staging of malignancies. Morphological overlap between reactive mesothelial cells and adenocarcinoma poses challenges, for which many immunohistochemical markers like BerEp4 and MOC-31 have been used extensively. Claudin4 is a new marker with promising results; however, further studies are required to establish its role as a pan-carcinoma marker in serous effusions. This study aimed to determine the utility of Claudin4 in diagnosing metastatic adenocarcinoma in effusions and comparing its performance with BerEp4.

METHODS

Claudin4 immunohistochemistry (IHC) was performed on effusion cell blocks (n = 60) reported as positive or suspicious for metastatic adenocarcinoma on cytology over a 1-year period and was scored for intensity (0-3) and percentage of positive cells (0-4). The results were compared with BerEp4 IHC and correlated with follow-up. Ten benign effusions were included as negative controls.

RESULTS

Claudin4 IHC was positive in all 60 (100%) cases, irrespective of the primary site. BerEp4 IHC was positive in 58 (96.7%) fluids and negative in 2 (3.3%) cases. All 10 benign effusions were negative for Claudin4 and BerEp4. Claudin4 showed higher intensity and proportion scores as compared to BerEp4 in cases where tumor cells were predominantly singly scattered and was comparable to BerEp4 where tumor cells were arranged in groups. Sensitivity, specificity, PPV, and NPV of Claudin4 in our study was 100%. Sensitivity, specificity, PPV, and NPV of BerEP4 was 96.7%, 100%, 100%, and 83.3%, respectively.

CONCLUSION

Claudin4 IHC staining results were comparable to BerEp4, irrespective of the primary site, and it performed better in cases where tumor cells were predominantly scattered singly.

Expert opinion on NSCLC small specimen biomarker testing - Part 1: Tissue collection and management

Biomarker testing is crucial for treatment selection in advanced non-small cell lung cancer (NSCLC). However, the quantity of available tissue often presents a key constraint for patients with advanced disease, where minimally invasive tissue biopsy typically returns small samples. In Part 1 of this two-part series, we summarise evidence-based recommendations relating to small sample processing for patients with NSCLC. Generally, tissue biopsy techniques that deliver the greatest quantity and quality of tissue with the least risk to the patient should be selected. Rapid on-site evaluation can help to ensure sufficient sample quality and quantity. Sample processing should be managed according to biomarker testing requirements, because tissue fixation methodology influences downstream nucleic acid, protein and morphological analyses. Accordingly, 10% neutral buffered formalin is recommended as an appropriate fixative, and the duration of fixation is recommended not to exceed 24–48 h. Tissue sparing techniques, including the ‘one biopsy per block’ approach and small sample cutting protocols, can help preserve tissue. Cytological material (formalin-fixed paraffin-embedded [FFPE] cytology blocks and non-FFPE samples such as smears and touch preparations) can be an excellent source of nucleic acid, providing either primary or supplementary patient material to complete morphological and molecular diagnoses. Considerations on biomarker testing, reporting and quality assessment are discussed in Part 2.

Effusion fluid cytology and COVID‐19 infection

Background

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), which is responsible for coronavirus disease 2019 (COVID‐19), is known to cause severe respiratory infections with occasional accompanying pleural effusion (PE), pericardial effusion (PCE), or peritoneal effusion (PTE). The effect of COVID‐19 on effusion cytology is not yet known. This study aimed to examine the cytomorphologic features and workup of effusion fluids in patients with active COVID‐19 infection versus those in recovery.

Methods

PE (n = 15), PCE (n = 1), and PTE samples (n = 20) from hospitalized patients with a SARS‐CoV‐2 infection (from June 1, 2020, to December 30, 2020) were reviewed. Effusion fluids with metastatic carcinoma were excluded. Differential cell counts, cytomorphology, and relevant immunostains for effusion fluids were retrospectively evaluated and compared between patients with active infection (positive on a SARS‐CoV‐2 nucleic acid amplification test [NAAT] within 2 months; n = 23) and those in the recovery phase from COVID‐19 (negative on a SARS‐CoV‐2 NAAT for >2 months; n = 13).

Results

The cytology diagnoses were negative for malignancy (n = 31), atypical (n = 4), and suspicious for malignancy (n = 1). Active infection cases showed more atypical mesothelial cells than recovery cases (P < .05); some had enlarged nuclei, prominent nucleoli, occasional multinucleation, and bizarre nuclei. Immunostains were performed more often in active infection cases than recovery cases (47.8% vs 7.7%; P < .05). Differential cell counts (available for 28 cases) showed no significant differences between the active infection and recovery groups.

Conclusions

This study found atypical and bizarre mesothelial cells more often in effusions of cases with active COVID‐19 infection in comparison with patients in recovery. It is important for cytopathologists to become familiar with the cytomorphologic effects of SARS‐CoV‐2 on effusion cytology so that these cases can be properly triaged.

This study examined the cytomorphologic features and work‐up of effusion fluids in patients with active COVID‐19 infection versus those in recovery, and found atypical and bizarre mesothelial cells to be present more often in effusions of cases with active COVID‐19 infection than those from patients in recovery. It is important for cytopathologists to become familiar with the cytomorphologic effects of SARS‐CoV‐2 on effusion cytology.

Application of the International System for Reporting Serous Fluid Cytopathology with Cytohistological Correlation and Risk of Malignancy Assessment

The International System for Reporting Serous Fluid Cytopathology (TIS) classifies serous effusions into five categories: non-diagnostic (ND), negative for malignancy (NFM), atypia of unknown significance (AUS), suspicious for malignancy (SFM) and malignant (MAL). The main objectives of this classification comprise the establishment of a universal code of communication between cytopathologists and clinicians and histopathologists, as well as between different laboratories worldwide, paving the way for the setting of clinical management guidelines based on the risk of malignancy assessment for each diagnostic category. We retrieved the total number of pleural and peritoneal effusion cases of our department for the three-year time period between 2018 and 2020, yielding a total of 528 and 500 cases, respectively. We then proceeded to reclassify each specimen according to TIS guidelines and calculate the risk of malignancy (ROM) for each category by searching each patients’ histology records, medical history and clinical follow-up. For pleural effusions, 3 (0.57%) cases were classified as ND, 430 (81.44%) cases as NFM, 15 (2.84%) as AUS, 15 (2.84%) as SFM and 65 (12.31%) as MAL. ROM amounted to 0%, 5.3%, 33.33%, 93.33% and 100% for each category, respectively. As far as peritoneal effusions are concerned, 6 (1.2%) were categorized as ND with ROM estimated at 16.66%, 347 (69.4%) as NFM (ROM = 9%), 13 (2.6%) as AUS (ROM = 38.46%), 12 (2.4%) as SFM (ROM = 83.33%) and 122 (24.4%) as MAL (ROM = 100%). Our results underline the utility of the current classification, both as a means of communication between doctors of different specialties and as general guidelines for the further clinical management of patients.

The value of a tiered cytology diagnostic reporting system in assessing the risk of malignancy in indeterminate serous effusions

BACKGROUND

The International System for Reporting Serous Fluid Cytopathology was recently proposed as a tiered structure to provide consistent reporting terminology for serous effusions. Because of the variation in reporting practices for indeterminate serous effusions, namely, the atypia of undetermined significance (AUS) and suspicious for malignancy (SFM) groups, the authors retrospectively reviewed cases in these 2 categories at their institution and determined the associated risk of malignancy (ROM).

METHODS

Pleural, peritoneal, and pericardial effusions that were reported as AUS or SFM over a 1-year period were reviewed, and their associated ROMs were calculated based on confirmation of malignancy by previous and/or subsequent fluid and/or tissue biopsy specimens from the same general location.

RESULTS

In total, 145 AUS and 98 SFM serous effusion cases were identified. The AUS category was used when the cells in question lacked the requisite quantitative (cell number) and/or qualitative (morphologic) features for a definitive diagnosis. Immunohistochemistry (IHC) or flow cytometry (FCM) was available in 15% of cases (n = 22) with inconclusive results. The ROM based on 69 cases with available follow-up results was 39%. In contrast, the SFM category demonstrated cells that were morphologically suspicious for malignancy but sparse, precluding IHC or FCM (n = 63; 64%) or yielding inconclusive results (n = 35; 36%). The ROM in the SFM category, based on follow-up results of 61 cases, was 64%.

CONCLUSIONS

The ROM for SFM was significantly higher than that for AUS (P < .01), supporting separate diagnostic categories for these 2 groups.