Numerous problems currently confront the proper pathologic diagnosis of low-grade serous neoplasia. Although diagnostic framework for low-grade serous neoplasia is complex, the literature supports distinct management algorithms and varying clinical outcomes for the spectrum of discrete diagnoses included within this category. However, given its ontological complexity and recent rapid evolution in classification and our understanding of these lesions, general pathologists struggle in the application of this complex diagnostic spectrum to individual cases. This shortfall applies not only to routine diagnosis, but to frozen section diagnosis, as well. In addition, the pathologist’s role is not only to affix diagnostic labels, but also to judiciously interpret diagnostically challenging or indeterminate cases and to guide clinical management using best available evidence. However, even among subspecialized gynecologic pathologists, appropriate diagnostic terminology in challenging cases of low-grade serous neoplasia can be evasive. This latter problem is further compounded by widespread unfamiliarity with the management implications of specific diagnoses.
This presentation will include a general overview of salient morphologic, immunohistochemical, and molecular features of low-grade serous neoplasms of the ovary, including:

1) Discussion of current morphologic criteria for diagnosis of common and uncommon variants of low-grade serous neoplasia, including prognostic and management implications of particular diagnoses.

2) Distinction between low-grade and high-grade serous carcinoma, where feasible, on the basis of established morphologic, immunophenotypic, and molecular criteria, as well as discussing the prognostic and management implications of an indeterminate diagnosis rendered on either biopsy or resection material.

3) Discussion of the molecular features of these neoplasms, including the relevant molecular alterations associated to progression of low-grade serous neoplasms from benign to malignant.
 

In this talk, I cover mesonephric and mesonephric-like proliferations of the female genital tract, including cervical mesonephric hyperplasia and mesonephric-like adenocarcinoma and the distinction between the two which can be problematic on occasions. Mesonephric-like adenocarcinoma (MLA) was introduced as a new tumour type in the endometrium and the ovary in the 2020 World Health Organization (WHO) Classification. This is a rare recently described (2016) and clinically aggressive carcinoma with a propensity for distant spread, especially to the lungs. MLA has a characteristic morphology and immunophenotype (hormone receptor negative or focally positive; TTF1 and/ or GATA3 positive) and are commonly associated with KRAS mutations. Although they show significant morphological, immunophenotypic and molecular overlap with cervical mesonephric adenocarcinomas, there are other parameters which suggest a Mullerian origin and, as such, the term MLA seems apt. MLA in the ovary is an endometriosis-associated neoplasm. I also discuss another putative mesonephric neoplasm, female adnexal tumour of Wolffian origin (FATWO) and the emergence of a new entity from this category, namely the STK11 adnexal tumour. The discovery of MLA and STK11 adnexal tumour represent examples of “new” entities still to this day being discovered through careful morphological observations and referral of cases for specialist opinion.