Architectural overlap between benign endocervix and pattern-A endocervical adenocarcinoma: Are all pattern-A tumors invasive?

Studies on the pattern-based classification for invasive endocervical adenocarcinoma showed that tumors with nondestructive invasion (pattern-A) have a 0% rate of nodal metastases. Our understanding of pattern-A tumors and their distinction from in-situ adenocarcinoma requires further study. Thirteen sections diagnosed independently as pattern-A adenocarcinoma by three gynecologic pathologists, and 14 sections of benign endocervix were selected. Three additional pathologists (reviewers) evaluated a digital image from each section and classified it as pattern-A or benign based on architecture only. To blind the interpretation to cytologic features, nuclei and cytoplasm were obscured using morphometric software (Zen 2011, Carl Zeiss Microscopy, Germany). 13/27 cases (48%; 8 pattern-A, 5 benign) were correctly classified by all reviewers; 19/27 (70%; 10 pattern-A, 9 benign) were correctly classified by ≥2 reviewers. 3/13 pattern-A cases (23%) were interpreted as benign by ≥2 reviewers. Conversely, 5/14 benign cervices (36%) were misinterpreted as pattern-A by ≥2 reviewers. The number of glands per 20× field was higher in pattern-A cases with high reviewer agreement (p=0.004). An abnormal architecture is seen in many pattern-A adenocarcinomas in support of their invasive nature; some, however, have architecture that overlaps with that of benign endocervix thus may actually represent in-situ lesions. Likewise, normal cervix can be architecturally complex and mirror patterns that pathologists would classify as pattern-A if malignant cytologic features were present. Based on this overlap and the nil risk of nodal spread, an emphasis on the non-destructive, rather than the invasive, nature of pattern-A adenocarcinoma is recommended.