Benign endometrial proliferations mimicking malignancies: a review of problematic entities in small biopsy specimens

Highly malignant endometrial stromal sarcoma in a cat

An 11-year-old female Persian cat underwent ovariohysterectomy due to dilation of the uterine cavity with irregular thickening of the wall. Macroscopically, the middle and distal regions of the left uterine horn were swollen and the uterine wall was irregularly thickened due to the development of multiple coalescent, variably sized nodules. Microscopically, the nodules had originated in the endometrium and were composed of round to polygonal neoplastic cells arranged in dense sheets or ill-defined fascicles. The neoplastic cells had locally invaded the myometrium and reached the subserosa, with lymphovascular invasion. Immunohistochemically, the neoplastic cell population was partially positive for CD10, an established marker of endometrial stromal sarcoma (ESS) in humans, with focal and diffuse nuclear immunopositivity for oestrogen and progesterone receptors and immunonegativity for desmin and α-smooth muscle actin. Based on these findings, the uterine tumour was diagnosed as ESS and was considered to correspond morphologically to high-grade ESS in humans.

Glandular Crowdings in Endometrial Polyps: Clinical Follow-Up and Possible Worrisome Features

INTRODUCTION

Interpretation of changes and premalignant lesions in endometrial polyps can be challenging. We evaluated the clinical course of patients with focal gland crowdings in endometrial polyps via repeat biopsies and searched for possible morphological findings in the initial biopsy that may foresee a premalignant course.

METHODS

Specimens diagnosed as endometrial polyp and focal gland crowding in patients who had a repeat biopsy in a 1-year period were reexamined. Morphological findings in the initial biopsies were recorded. The group whose repeat biopsies were "premalignant or malignant" (Group 1), and the group with "benign" repeat biopsies (Group 2) were compared.

RESULTS

"Endometrial polyp and gland crowdings" was diagnosed in 115 specimens of which 38 patients had repeat biopsies. Among these 8 (21%) were diagnosed as "endometrial intraepithelial neoplasia (EIN)" (Group 1) and 30 (79%) as "benign" (Group 2). Morphological features in the initial biopsies were evaluated; PAX2 loss was 6 of 8 (75%) for Group 1 and 7 of 30 (23%) for Group 2 (P = .020), and altered epithelial cytological features were present in 5 of 8 (62%) versus 4 of 30 (13%) (P = .015), both significantly higher in Group 1. Dark intraluminal secretion, intraluminal histiocytes, intraglandular epithelial proliferation, and mean diameter of crowded gland areas were not statistically different between the 2 groups.

CONCLUSION

"Focal gland crowdings" in endometrial polyps do carry a risk of EIN in subsequent biopsies. We suggest that the loss/decrease of PAX2 and altered epithelial cytological features in these areas in the initial biopsy are indicative of a premalignant course.

Endometrioid Squamous Proliferations of the Endometrium Express Alpha-Methylacyl-CoA Racemase (P504s)

Squamous morular metaplasia is closely associated with endometrioid proliferative lesions such as endometrial intraepithelial neoplasia, whereas endometrioid adenocarcinoma may also demonstrate squamous differentiation (morular or nonmorular). Alpha-methylacyl-CoA racemase (AMACR; P504s) is an immunohistochemistry marker expressed in many tumors, including prostate adenocarcinoma, renal cell carcinoma, and in a subset of gynecologic carcinomas, predominantly of clear cell histology. In small biopsy samples, the distinction between cervical high-grade squamous intraepithelial lesions (HSILs) involving endocervical glands from endometrioid squamous proliferations can be challenging, given their anatomic vicinity and some degree of morphologic overlap. Following the observation of AMACR positivity by immunohistochemistry within squamous morules in an index case, 35 endometrial samples containing squamous morular metaplasia (25) and nonmorular squamous metaplasia (10), and 32 cases of cervical HSIL involving endocervical glands were stained with AMACR. The endometrial cohort consisted of 2 benign anovulatory endometrium, 7 endometrial polyps, 7 endometrial intraepithelial neoplasia, 4 atypical polypoid adenomyomas, and 15 endometrioid adenocarcinomas. Positive cases were scored as diffuse (≥50%) or focal (<50%). AMACR staining was present in 96.7% of endometrial squamous lesions, including 14 (93.3%) of endometrioid carcinomas, and in all cases of endometrial intraepithelial neoplasia, endometrial polyps, atypical polypoid adenomyomas, and anovulatory endometrium with squamous morular metaplasia or nonmorular squamous metaplasia. In comparison, only 2 cases (5.8%) of cervical HSIL demonstrated positivity for AMACR. In conclusion, AMACR can reliably differentiate the cervical versus endometrial origin of squamous lesions in small biopsy specimens.

Patterns of Error in Interpretive Pathology

OBJECTIVES

To demonstrate how the educational presentation and targeted review of cases with discrepant interpretive findings between pathologists can raise awareness for specific diagnostic errors through identification of common overarching patterns of error in interpretive pathology.

METHODS

We performed a review of 147 surgical pathology and cytopathology cases of discordances from 23 PowerPoint presentations presented between 2010 and 2017. Pathologists and pathology residents, blinded from the official interpretations, were presented each case and surveyed for their own diagnostic assessments. Survey results were compared with the final/correct interpretations of the signing pathologists.

RESULTS

Of the 134 cases with available survey results, there were 87 (64.9%) for which most survey respondents proposed a diagnostic interpretation concordant with the final/correct diagnosis. There were 37 (27.6%) cases for which most survey responses were either wholly or partially discordant with the final/correct diagnosis. For 10 (7.5%) cases, there were equal numbers of concordant and discordant survey responses.

CONCLUSIONS

Our analyses of the cases with frequent erroneous diagnoses reveal common patterns of error that are widely applicable and outline specific error-prone interpretive tendencies. Greater awareness for these tendencies, highlighted by presentation of discordant cases, can improve the quality of diagnostic pathology services.

Clinical validation of a next-generation sequencing-based multi-cancer early detection "liquid biopsy" blood test in over 1,000 dogs using an independent testing set: The CANcer Detection in Dogs (CANDiD) study

Cancer is the leading cause of death in dogs, yet there are no established screening paradigms for early detection. Liquid biopsy methods that interrogate cancer-derived genomic alterations in cell-free DNA in blood are being adopted for multi-cancer early detection in human medicine and are now available for veterinary use. The CANcer Detection in Dogs (CANDiD) study is an international, multi-center clinical study designed to validate the performance of a novel multi-cancer early detection “liquid biopsy” test developed for noninvasive detection and characterization of cancer in dogs using next-generation sequencing (NGS) of blood-derived DNA; study results are reported here. In total, 1,358 cancer-diagnosed and presumably cancer-free dogs were enrolled in the study, representing the range of breeds, weights, ages, and cancer types seen in routine clinical practice; 1,100 subjects met inclusion criteria for analysis and were used in the validation of the test. Overall, the liquid biopsy test demonstrated a 54.7% (95% CI: 49.3–60.0%) sensitivity and a 98.5% (95% CI: 97.0–99.3%) specificity. For three of the most aggressive canine cancers (lymphoma, hemangiosarcoma, osteosarcoma), the detection rate was 85.4% (95% CI: 78.4–90.9%); and for eight of the most common canine cancers (lymphoma, hemangiosarcoma, osteosarcoma, soft tissue sarcoma, mast cell tumor, mammary gland carcinoma, anal sac adenocarcinoma, malignant melanoma), the detection rate was 61.9% (95% CI: 55.3–68.1%). The test detected cancer signal in patients representing 30 distinct cancer types and provided a Cancer Signal Origin prediction for a subset of patients with hematological malignancies. Furthermore, the test accurately detected cancer signal in four presumably cancer-free subjects before the onset of clinical signs, further supporting the utility of liquid biopsy as an early detection test. Taken together, these findings demonstrate that NGS-based liquid biopsy can offer a novel option for noninvasive multi-cancer detection in dogs.

2020 WHO Classification of Female Genital Tumors

The 2020 WHO classification is focused on the distinction between HPV-associated and HPV-independent squamous cell carcinoma of the lower female genital organs. Differentiating according to HPV association does not replace the process of grading; however, the WHO classification does not recommend any specific grading system. VIN are also differentiated according to whether they are HPV(p16)-associated. HPV-independent adenocarcinoma (AC) of the cervix uteri has an unfavorable prognosis. Immunohistochemical p16 expression is considered to be a surrogate marker for HPV association. HPV-associated AC of the cervix uteri is determined using the prognostically relevant Silva pattern.

[Current WHO classification of the female genitals : Many new things, but also some old]

The new WHO classification of tumors of the female genitalia entails some changes, especially those of prognostic and therapeutic relevance: there is a return to the term borderline tumor. Implants are again subdivided into noninvasive implants of the epithelial or desmoplastic type as before. Invasive extraovarian implants are classified as low-grade serous carcinoma (LGSC). Former seromucinous carcinomas are now classified as endometrioid carcinomas (seromucinous subtype). New entities of ovarian carcinomas are mesonephric-like adenocarcinoma, undifferentiated and dedifferentiated carcinoma, and mixed carcinoma. The classification of neuroendocrine neoplasms is analogous to that of pulmonary and gastrointestinal neuroendocrine neoplasms, regardless of their location. Endometrioid endometrial carcinoma can be classified into four molecular subtypes, which have significant prognostic significance. New subtypes include mucinous carcinoma of the intestinal type and mesonephric-like adenocarcinoma. Stromasarcomas of the endometrium are further subclassified based on specific molecular alterations. Adenocarcinomas (ACs) and squamous cell carcinomas (PECs) of the lower female genital tract are distinguished from HPV-associated and HPV-independent carcinomas. Block-like staining for p16 is the accepted surrogate immunohistochemical marker. Grading has not been reported for PEC. For HPV-associated AC of the cervix uteri, prognostic assessment is based on the pattern of invasion (so-called Silva pattern). Serous carcinomas in the cervix uteri are endometrial carcinomas with cervical infiltration.