Incidental FOXL2 mutated adult granulosa cell tumour of the ovary with thecoma-like foci

Abstract

We report on the incidental finding of a FOXL2 mutated adult granulosa cell tumour of the ovary with thecoma-like foci, a rare entity recently described by Jennifer N. Stall and Robert H. Young in a series of sixteen cases in 2019, displaying features differing from conventional adult granulosa cell tumour. Our aim is to specify the morphologic and molecular particularities of this presumably underrecognized finding, with a short presentation of the typical clinical context. Awareness of this rare and challenging neoplasm with indeterminate clinical course is crucial in routine diagnostics.

Sex Cord–Stromal Tumors of the Ovary: An Update and Review. Part I — Pure Ovarian Stromal Tumors

“…76 A reticulin stain is often most helpful in this setting as it highlights reticulin fibers surrounding individual tumor cells in a thecoma or around groups of cells in a granulosa cell tumor even in those with a thecoma-like appearance. The presence of a FOXL2 mutation favors an AGCT 90 although they may be less frequent in tumors with a fibromatous/thecomatous background. 91 Rare FOXL2 mutations have been reported in thecomas, although it is unclear if these may represent thecoma-like granulosa cell tumors.…”

Relevance of Molecular Pathology for the Diagnosis of Sex Cord–Stromal Tumors of the Ovary: A Narrative Review

“…The reticulin stain surrounds individual cells [43] and can be very useful, especially in distinguishing thecomas with luteinized changes from luteinized adult granulosa cell tumors, which is the most clinically important differential diagnosis, largely resolved by accurate sampling [41]. This is especially true since thecoma-like foci have been described in adult granulosa cell tumors [45,46]. When minor sex cord elements are present, the reticulin stain shows cell cords or nests without individual wrapping [8,32,35].…”

“…Only few studies have focused on the molecular biology of pure thecomas; some authors have reported a FOXL2 variant in this neoplasm [47]. However, to date, there is some controversy about this evidence [8,19,41] as these may correspond to adult granulosa cell tumors with a predominant thecoma-like or luteinized component [45,46]. The morphological distinction between granulosa cell tumors and thecomas can be difficult and arbitrary [47].…”