Editors: Rouzan Karabakhtsian, MD, PhD, professor of pathology and director of the Women’s Health Pathology Fellowship, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY; Shaomin Hu, MD, PhD, staff pathologist, Cleveland Clinic; S. Emily Bachert, MD, breast pathology fellow, Brigham and Women’s Hospital, Boston; and Amarpreet Bhalla, MD, assistant professor of pathology, Albert Einstein College of Medicine, Montefiore Medical Center.
Interobserver agreement in pathologic evaluation of bile duct biopsies
April 2021—Intraductal biopsy is commonly used preoperatively to evaluate the etiology of biliary strictures. It can be challenging to interpret intraductal biopsies. The diagnosis is often hindered by interobserver disagreement. The authors conducted a study to assess interobserver concordance when interpreting intraductal biopsies. They retrieved 85 biopsies that fell into five diagnostic categories: negative for dysplasia, indefinite for dysplasia, low-grade dysplasia, high-grade dysplasia, and carcinoma. Eight gastrointestinal pathologists blindly reviewed all the slides for the study. Agreement among pathologists was analyzed using Fleiss κ and weighted concordance coefficient S*. A face-to-face consensus/training session was held to discuss the classification criteria, followed by a second round review. The overall interobserver agreement was fair in the first round review (κ = 0.39, S* = 0.56) and improved to moderate in the second round review (κ = 0.48, S* = 0.69). The agreement before and after the consensus meeting was substantial to nearly perfect for carcinoma (κ = 0.65, S* = 0.83 and κ = 0.80, S* = 0.91), fair for high-grade dysplasia (κ = 0.28, S* = 0.69 and κ = 0.40, S* = 0.63), and moderate for negative for dysplasia (κ = 0.47, S* = 0.50 and κ = 0.47, S* = 0.53). Agreement improved from fair to moderate for low-grade dysplasia (κ = 0.36, S* = 0.61 to κ = 0.49, S* = 0.71) and slight to fair for indefinite for dysplasia (κ = 0.16, S* = 0.51 to κ = 0.33, S* = 0.50). When compared with Hollande’s fixed specimens, the agreement was higher in almost all diagnostic categories for the formalin-fixed specimens. Overall, interobserver concordance was improved after a consensus/training session. The authors concluded that their data suggest that obtaining second opinions and consensus among groups and gathering previous cases for the training sets among groups would help improve agreement in clinical practice. However, additional studies, involving greater numbers of pathologists and institutions, are needed to better define the diagnostic criteria for biliary dysplasia/neoplasia and improve the reproducibility of diagnosis.
Liu YJ, Rogers J, Liu YZ, et al. Interobserver agreement in pathologic evaluation of bile duct biopsies. Hum Pathol. 2021;107:29–38.
Correspondence: Dr. Matthew M. Yeh at myeh@uw.edu
Small core needle biopsies in cytology practice: an ASC member survey
The introduction of a new generation of core needle biopsies for endoscopic procedures has prompted reconsideration of cytopathologists’ handling of small biopsies. Therefore, the American Society of Cytopathology (ASC) conducted a survey to elucidate current practices for handling small core needle biopsies (CNBs). All ASC members were invited by email to participate in an online survey over a two-month period. The survey consisted of 20 multiple-choice questions with two to eight answer options per question. Of 2,651 members contacted by email, 282 (10.6 percent) responded to the survey, including 196 (69.5 percent) pathologists and 86 (30.5 percent) cytotechnologists. Of this group, 265 (94 percent) respondents were from the United States or Canada, with 156 (58.9 percent) from academic institutions and 109 (41.1 percent) from non-academic practices. Seventeen (six percent) respondents were from other countries. The survey found that in 18.8 percent of practices, cytopathologists signed out more than 90 percent of small CNBs from endoscopic and radiologically guided procedures. In 36.5 percent of practices, more than 90 percent were signed out by surgical pathologists. The remaining practices had such cases divided more evenly between cytopathologists and surgical pathologists. The findings showed that 78 percent of respondents were interested in signing out more small biopsies in the future, and 80.5 percent desired increased small biopsy-related resources from the ASC.
Thrall MJ, Vrbin C, Barkan GA, et al. Small core needle biopsies in cytology practice: a survey of members of the American Society of Cytopathology. J Am Soc Cytopathol. 2020;9:310–321.
Correspondence: Dr. Michael J. Thrall at mjthrall@houstonmethodist.org
Use of IHC markers to distinguish endometrial clear cell carcinoma
from its morphologic mimics
The diagnosis of clear cell (CC) carcinoma of the endometrium can be challenging, especially when endometrioid (EC) and serous (SC) endometrial cancers exhibit nonspecific clear cell changes in carcinomas with mixed histology and in the setting of Arias-Stella reaction. The authors conducted a study to assess the classic CC IHC markers napsin A, HNF-1β, and estrogen receptor (ER) and the two recent novel markers cystathionine gamma-lyase (CTH) and arginosuccinate synthase (ASS1) for their utility in distinguishing CC from its morphologic mimics. For the study, tissue microarrays containing 64 CC, 128 EC, five EC with clear-cell changes, 16 SC, five mixed carcinomas, and 11 whole Arias-Stella reaction (ASR) sections were stained. Twelve additional examples of ASR were stained subsequently. A cutoff of 70 percent and moderate intensity were used for HNF-1β; 80 percent of cells and strong intensity were used for CTH; and any staining was considered positive for the remaining markers. HNF-1β, napsin A, and CTH performed well for differentiating CC from pure EC and SC. HNF-1β had higher specificity (99.3 versus 95.1 percent) but lower sensitivity (55.8 versus 73.1 percent) than napsin A. CTH did not substantially outperform HNF-1β or napsin A (sensitivity, 51.9 percent; specificity, 99.3 percent). ASS1 and ER were not helpful (specificity, 60.1 and 22.6 percent, respectively). HNF-1β, napsin A, and CTH stained a large proportion of ASR and were not useful for differentiating CC from ASR. However, ER positivity and ASS1 negativity were helpful for identifying ASR (specificity, 88.2 and 95.1 percent, respectively). EC with clear-cell changes exhibited IHC patterns similar to pure EC (HNF-1β-, ER+, and CTH-). No markers were useful for confirming the CC components in mixed carcinomas.
Ji JX, Cochrane DR, Tessier-Cloutier B, et al. Use of immunohistochemical markers (HNF-1β, napsin A, ER, CTH, and ASS1) to distinguish endometrial clear cell carcinoma from its morphologic mimics including Arias-Stella reaction. Int J Gynecol Pathol. 2020;39(4):344–353.
Correspondence: Dr. Lynn N. Hoang at lien.hoang@vch.ca
Receptor conversion in metastatic breast cancer
Estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2) status provide clinical utility in guiding therapeutic decision-making in metastatic breast cancer. Data increasingly have shown substantial differences between the receptor profiles of primary breast cancers and their paired metastases. The authors conducted a study in which they used a large single-center cohort to assess the frequency of receptor conversion in metastatic breast cancer. The overall discordance rates were 18.3 percent, 40.3 percent, and 13.7 percent for estrogen receptor (ER), progesterone receptor (PR), and HER2, respectively. The discordance was significantly higher for PR than for ER and HER2. The occurrence of conversion was significant as a switch from positive to negative receptor status versus as a switch from negative to positive status for all three receptors. Semiquantitative analyses revealed a significantly decreased expression of ER (25 percent) and PR (57 percent) in the metastases. A higher rate of PR discordance was found in bone metastases when compared with other common organs of relapse. Furthermore, in the subset of patients with a single primary and multiple distant metastases, the discordance rates among the distant sites were 27.5 percent, 39.4 percent, and 14.3 percent for ER, PR, and HER2, respectively. Positive ER status in primary or metastatic breast cancer was associated with prolonged metastasis-free survival when compared with that in ER-negative primary tumors without conversion. Furthermore, positive ER status in metastatic breast cancer regardless of primary was associated with superior overall survival when compared with ER-negative tumors without conversion. In summary, receptor conversion is a frequent event in the course of breast cancer progression, and both positive to negative and negative to positive conversions are clinically relevant. In addition, discordance in receptor status between different metastatic sites was observed in a significant proportion of metastatic breast cancer patients. Moreover, some conversions were of prognostic significance. The findings may reflect tumor heterogeneity, sampling, or treatment effect but may also indicate alteration in tumor biology. Repeat biomarker testing is warranted in developing appropriate treatment plans in the pursuit of precision medicine.
Chen R, Qarmali M, Siegal GP, et al. Receptor conversion in metastatic breast cancer: analysis of 390 cases from a single institution. Mod Pathol. 2020;33:2499–2506.
Correspondence: Dr. Shi Wei at swei@uabmc.edu
Analysis of p53 IHC patterns in HPV-related neoplasms of female lower genital tract
The authors encountered p53 IHC patterns in human papillomavirus-associated carcinomas of the gynecologic tract, which were confused with an absence or overexpression of TP53 mutational staining. Therefore, they evaluated p53 and p16 IHC in 25 squamous cell carcinomas (SCC; 16 vulva, four Bartholin’s gland, and five cervix), 20 endocervical adenocarcinomas (EDAC), 14 high-grade squamous intraepithelial lesions (HSIL), and two adenocarcinoma in situ (AIS), all of which exhibited morphologic features of human papillomavirus (HPV). Only cases showing diffuse/strong block-like p16 staining were included for further study. All EDACs underwent TP53 sequencing, and HPV in situ hybridization was performed in select cases. P53 IHC staining fell into two main patterns. The most common was designated “markedly reduced (null like)” and was characterized by absence of staining or significantly attenuated staining in more than 70 percent of cells. This was present in 14 of 25 (56 percent) SCCs, seven of 14 (50 percent) HSILs, and 18 of 20 (90 percent) EDACs. The other notable pattern was “mid-epithelial (basal sparing),” which was defined as a distinct absence of staining in basal cells juxtaposed with strong staining in parabasal cells. It was seen in 10 of 25 (40 percent) SCCs, seven of 14 (50 percent) HSILs, and none of the EDACs. Scattered weak to moderate p53 staining (conventional wild type) was noted in one of 25 (four percent) SCCs and two of 20 (10 percent) EDACs. No cases showed strong/diffuse overexpression. One EDAC had a TP53 missense mutation and exhibited markedly reduced (null-like) staining. HPV in situ hybridization revealed an inverse relationship with p53—cells positive for HPV mRNA were negative for p53. The authors concluded that knowledge of these patterns can help pathologists avoid misinterpreting p53 status in HPV-associated cancers.
Thompson EF, Chen J, Huvila J, et al. p53 immunohistochemical patterns in HPV-related neoplasms of the female lower genital tract can be mistaken for TP53 null or missense mutational patterns. Mod Pathol. 2020;33(9):1649–1659.
Correspondence: Dr. Lynn Hoang at lien.hoang@vch.ca
Comparing Ki-67 labeling index on small biopsy versus resection using tumor tracing and hot spot methods
Pulmonary carcinoids are classified as typical or atypical by assessing necrosis and mitoses, which usually cannot be adequately assessed on small biopsies. Ki-67 is not used to grade pulmonary carcinoids, but it may be helpful to determine preliminary grade in biopsies. However, the rate at which Ki-67 could underestimate or overestimate grade on small biopsies has not been well studied. The authors conducted a study in which they compared Ki-67 labeling obtained on small biopsies to subsequent resection. Ki-67 was performed on paired biopsy and resection specimens from 55 patients. Slides were scanned using the Aperio ScanScope. Ki-67 labeling index was determined using automated hot spot and tumor tracing methods. The study included 41 typical and 14 atypical carcinoids. Atypical carcinoids were larger and had more distant metastases. Death from disease occurred in three patients, all of whom had atypical carcinoids. The median hot spot Ki-67 labeling index was greater in resection compared with biopsy by 0.7 percent (P = .02). The median tumor tracing Ki-67 was lower in resection compared with biopsy by 0.5 percent (P < .001). Receiver operating characteristic analysis showed similar hot spot Ki-67 cutoffs for predicting atypical histology (3.5 percent for biopsy, 3.6 percent for resection; area under the curve [AUC], 0.75 and 0.74, respectively). Different optimal cutoffs were needed for the tracing method based on biopsy (2.1 percent; AUC, 0.75) compared with resection (1.0 percent; AUC, 0.67). The authors concluded that hot spot Ki-67 tends to underestimate grade on small biopsies, whereas grade is overestimated by tumor tracing. A hot spot Ki-67 cutoff of 3.5 percent predicted atypical histology in biopsy and resection specimens. Different biopsy and resection cutoffs were necessary for tumor tracing, which would make clinical implementation more difficult.
Boland JM, Kroneman TN, Jenkins SM, et al. Ki-67 labeling index in pulmonary carcinoid tumors: comparison between small biopsy and resection using tumor tracing and hot spot methods. Arch Pathol Lab Med. 2020;144(8):982–990.
Correspondence: Dr. Jennifer M. Boland at boland.jennifer@mayo.edu
Use of SOX6 to differentiate epithelioid mesothelioma from lung adenocarcinoma
The ability to differentiate epithelioid mesothelioma from lung adenocarcinoma using immunohistochemistry is improving. However, IHC markers with high sensitivity and specificity have yet to be identified. The authors conducted a study in which they investigated the utility of sex-determining region Y box 6 (SOX6) as a novel IHC marker, identified by analyzing previous gene-expression data. SOX6 was expressed in 53 of 54 (98 percent) cases of epithelioid mesothelioma compared to five of 69 (seven percent) cases of lung adenocarcinoma. The sensitivity and specificity of SOX6 expression for differentiating epithelioid mesothelioma and lung adenocarcinoma were 98 percent and 93 percent, respectively. SOX6 expression showed similar sensitivity and far better specificity than did that of calretinin or podoplanin (D2-40). In addition, SOX6 expression was more sensitive than Wilms tumor 1 expression. A combination of SOX6 and other markers showed comparable or better sensitivity and specificity than did other combinations. The sensitivity of positivity for SOX6 and calretinin (96 percent) and the specificity of positivity for SOX6 and Wilms tumor 1 (93 percent) were higher than those of the other combinations. The authors concluded that SOX6 is a novel candidate IHC marker for differentiating epithelioid mesothelioma from lung adenocarcinoma.
Kambara T, Amatya VJ, Kushitani K, et al. SOX6 is a novel immunohistochemical marker for differential diagnosis of epithelioid mesothelioma from lung adenocarcinoma. Am J Surg Pathol. 2020;44(9):1259–1265.
Correspondence: Dr. Yukio Takeshima at ykotake@hiroshima-u.ac.jp