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We sought to classify endocervical adenocarcinomas (ECAs) based on morphologic features linked to etiology (ie, human papillomavirus [HPV] infection), unlike the World Health Organization 2014 classification. The International Endocervical Adenocarcinoma Criteria and Classification (IECC criteria), described herein, distinguishes between human papillomavirus-associated adenocarcinoma (HPVA), recognized by the presence of luminal mitoses and apoptosis seen at scanning magnification, and no or limited HPVA features (nonhuman papillomavirus-associated adenocarcinoma [NHPVA]). HPVAs were then subcategorized based on cytoplasmic features (mostly to provide continuity with preexisting classification schemes), whereas NHPVAs were subclassified based on established criteria (ie, gastric-type, clear cell, etc.). Complete slide sets from 409 cases were collected from 7 institutions worldwide. Tissue microarrays representing 297 cases were constructed; immunohistochemistry (p16, p53, vimentin, progesterone receptor) and chromogenic in situ hybridization using an RNA-based probe set that recognizes 18 varieties of high-risk HPV were performed to validate IECC diagnoses. The 5 most common IECC diagnoses were usual-type (HPVA) (73% of cohort), gastric-type (NHPVA) (10%), mucinous adenocarcinoma of HPVA type, including intestinal, mucinous not otherwise specified, signet-ring, and invasive stratified mucin-producing carcinoma categories (9%), clear cell carcinoma (NHPVA) (3%) and adenocarcinoma, not otherwise specified (2%). Only 3 endometrioid carcinomas were recognized and all were NHPVA. When excluding cases thought to have suboptimal tissue processing, 90% and 95% of usual-type IECC cases overexpressed p16 and were HPV, whereas 37% and 3% of NHPVAs were p16 and HPV, respectively. The 1 HPV gastric-type carcinoma was found to have hybrid HPVA/NHPVA features on secondary review. NHPVA tumors were larger and occurred in significantly older patients, compared with HPVA tumors (P<0.001). The high-risk HPV chromogenic in situ hybridization probe set had superior sensitivity, specificity, and positive and negative predictive values (0.955, 0.968, 0.992, 0.833, respectively) compared with p16 immunohistochemistry (0.872, 0.632, 0.907, 0.545, respectively) to identify HPV-related usual carcinoma and mucinous carcinoma. IECC reliably segregates ECAs into HPVA and NHPVA types using morphology alone. This study confirms that usual-type ECAs are the most common type worldwide and that mucinous carcinomas comprise a mixture of HPVA and NHPVA, with gastric-type carcinoma being the major NHPVA type. Endometrioid and serous carcinomas of the endocervix are extraordinarily rare. Should clinical outcomes and genomic studies continue to support these findings, we recommend replacement of the World Health Organization 2014 criteria with the IECC 2017.

Tropomyosin receptor kinase (Trk) inhibitors have shown high response rates in patients with tumors harboring NTRK fusions. We identified 4 NTRK fusion-positive uterine sarcomas that should be distinguished from leiomyosarcoma and undifferentiated uterine sarcoma. NTRK rearrangements were detected by fluorescence in situ hybridization (FISH) and/or targeted RNA or DNA sequencing in 4 undifferentiated uterine sarcomas with spindle cell morphology. Because of histologic overlap with leiomyosarcoma, TrkA and pan-Trk immunohistochemistry was performed in 97 uterine leiomyosarcomas. NTRK1 and NTRK3 FISH was performed on tumors with TrkA or pan-Trk staining. We also performed whole transcriptome RNA sequencing of a leiomyosarcoma with TrkA expression and targeted RNA sequencing of 2 additional undifferentiated uterine sarcomas. FISH and/or targeted RNA or DNA sequencing in the study group showed TPM3-NTRK1, LMNA-NTRK1, RBPMS-NTRK3, and TPR-NTRK1 fusions. All tumors were composed of fascicles of spindle cells. Mitotic index was 7 to 30 mitotic figures per 10 high power fields; tumor necrosis was seen in 2 tumors. Desmin, estrogen receptor, and progesterone receptor were negative in all tumors, while pan-Trk was expressed in all tumors with concurrent TrkA staining in 3 of them. TrkA and/or pan-Trk staining was also seen in 6 leiomyosarcomas, but these tumors lacked NTRK fusions or alternative isoforms by FISH or whole transcriptome sequencing. No fusions were detected in 2 undifferentiated uterine sarcomas. NTRK fusion-positive uterine spindle cell sarcomas constitute a novel tumor type with features of fibrosarcoma; patients with these tumors may benefit from Trk inhibition. TrkA and pan-Trk expression in leiomyosarcomas is rare and does not correlate with NTRK rearrangement.

Patients with high-grade subtypes of endometrial carcinoma (grade 3 endometrioid, serous, clear cell, or carcinosarcoma) have a relatively poor prognosis. The specific subtype may be used to guide patient management, but there is little information on the reproducibility of subtype diagnosis in cases of high-grade endometrial carcinoma. Fifty-six cases diagnosed as a high-grade subtype of endometrial carcinoma were identified from the pathology archives of Vancouver General Hospital. All slides for each case were reviewed independently by 3 pathologists, who diagnosed the specific tumor subtype(s) and assigned the percentage of each subtype for mixed tumors. Agreement between observers was categorized as follows: major disagreement: (A) no consensus for low-grade endometrioid versus high-grade carcinoma (any subtype), or (B) no consensus with respect to the predominant high-grade subtype present; minor disagreement: consensus was reached about the cell type of the predominant component of a mixed tumor, but there was disagreement about the subtype of the minor component. A tissue microarray was constructed from these cases and immunostained for p16, ER, PR, PTEN, and p53. In 35 of 56 (62.5%) cases, there was agreement between all 3 reviewers regarding the subtype diagnosis of the exclusive (in pure tumors) or predominant (in mixed tumors) high-grade component. Of these cases, there was a minor disagreement (ie, disagreement about the minor high-grade component subtype in a mixed tumor) in 4 cases (4/56, 7.1%). In 20 of 56 (35.8%) cases there was a major disagreement; in 17 (30.4%) of these cases there was no consensus about the major subtype diagnosis, whereas in 3 (5.4%) cases there was disagreement about whether a component of high-grade endometrial carcinoma was present. In the final case, all 3 reviewers diagnosed the case as low-grade endometrioid carcinoma, disagreeing with the original diagnosis of high-grade carcinoma. The most frequent areas of disagreement were serous versus clear cell (7 cases) and serous versus grade 3 endometrioid (6 cases). Immunostaining results using the 5-marker immunopanel were then used to adjudicate in the 6 cases in which there was disagreement between reviewers with respect to serous versus endometrioid carcinoma, and these supported a diagnosis of serous carcinoma in 4 of 6 cases and endometrioid carcinoma in 2 of 6 cases. Pairwise comparison between the reviewers for the 20 cases classified as showing major disagreement was as follows: reviewer 1 and reviewer 2 agreed in 5/20 cases, reviewer 1 and reviewer 3 agreed in 7/20 cases, and reviewer 2 and reviewer 3 agreed in 8/20 cases, indicating that disagreements were not because of a single reviewer holding outlier opinions. Diagnostic consensus among 3 reviewers about the exclusive or major subtype of high-grade endometrial carcinoma was reached in only 35/56 (62.5%) cases, and in 4 of these cases there was disagreement about the minor component present. This poor reproducibility did not reflect systematic bias on the part ...