Costantino Ricci

FoxA2 is a reliable marker for the diagnosis of yolk sac tumour postpubertal‐type

AimsYolk sac tumour postpubertal‐type (YSTpt) shows a wide range of histological patterns and is challenging to diagnose. Recently, forkhead box transcription factor A2 (FoxA2) emerged as a driver of YSTpt formation and a promising marker for diagnosing YSTpt. However, FoxA2 has not been tested in the different patterns of YSTpt. This study aimed to assess the staining pattern of FoxA2 in te different patterns of YSTpt and other germ cell tumours of the testis (GCTT), comparing it with glypican‐3 (GPC3) and α‐fetoprotein (AFP).Methods and resultsFOXA2, GPC3 and AFP immunohistochemistry was performed on 24 YSTpt (24 microcystic/reticular, 10 myxoid, two macrocystic, five glandular/alveolar, two endodermal sinus/perivascular, four solid, two polyembryoma/embryoid body and two polyvesicular vitelline) and 81 other GCTT. The percentage of positive cells (0, 1+, 2+, 3+) and the intensity (0, 1, 2, 3) were evaluated regardless of and within each YSTpt pattern. FoxA2 was positive in all YSTpt (24 of 24) and all but one (23 of 24) exhibited 2+/3+ stain, with higher intensity [median value (mv): 2.6] than AFP (1.8) and GPC3 (2.5). Both FoxA2 and GPC3 were positive in all microcystic/reticular (24 of 24), myxoid (10 of 10), macrocystic (two of two), endodermal sinus/perivascular (four of four) and polyembryoma/embryoid body (two of two) patterns. Nevertheless, only FoxA2 was positive in all glandular/alveolar (five of five), solid (four of four) and polyvesicular vitelline (two of two) patterns. The intensity of FoxA2 was higher than AFP and GPC3 in almost all YST patterns. In the other GCTT, FoxA2 was positive only in teratoma postpubertal‐type (Tpt) [13 of 20 (65%)], with staining almost exclusively confined to the mature gastrointestinal/respiratory tract epithelium.ConclusionsFoxA2 is a highly sensitive and specific biomarker that supports the diagnosis of YSTpt. FoxA2 is superior to GPC3 and AFP, especially in rare and difficult‐to‐diagnose histological patterns of YSTpt, but mature glands of Tpt could represent a potential diagnostic pitfall.

Immunophenotypical assessment supports that post‐chemotherapy glandular tumours of germ cell origin straddle between glandular yolk sac tumour and ‘somatic‐type’ adenocarcinoma

Adult granulosa cell tumours of the testis analogous to ovarian counterparts are exceptionally rare: analysis of a multicentric series and review of the literature

Aims Testicular adult granulosa cell tumours (AGCTs) are rare and show several clinical–pathological differences with their ovarian counterparts. In a limited number of prior studies, FOXL2 p.Cys134Trp, the hallmark molecular alteration of ovarian AGCT, appeared to be infrequent in testicular AGCTs. However, the number of cases analysed to date is relatively small. Methods and results Twenty testicular AGCTs were analysed de novo using two different next‐generation sequencing ( NGS ) panels that cover sex cord‐stromal tumour ( SCST )–relevant genes, including FOXL2 , CTNNB1 , FH and DICER1 . Among 12 tumours (12/20; 60%) that were sequenced successfully, none harboured FOXL2 mutations. Eight tumours (8/12, 66.7%) showed a wild‐type ( WT ) status for all genes assessed with the panels. Three tumours harboured pathogenic or likely pathogenic CTNNB1 alterations. One of these exhibited predominant spindle cell morphology, while the other two showed focal tubular architecture. Immunohistochemistry performed in one of these tumours with available material showed β‐catenin expression in ~70% of tumor cell nuclei. The remaining AGCTs showed variants of uncertain significance (likely benign) in KIT and MED12 . Considering the tumors asseseed in this study and those previously reported in the literature, only 2 of 29 neoplasms classified as testicular AGCTs have shown a FOXL2 p. Cys134Trp mutation to date. Conclusions The present study confirms that SCSTs classified as AGCTs differ from their ovarian counterparts in that they largely lack FOXL2 mutations.

Analysis of HNF1β expression suggests that its downregulation is involved in the sarcomatoid transformation of yolk sac tumor

Sarcomatoid yolk sac tumor postpubertal-type (YSTpt) is a rare phenotype of germ cell tumor that occurs mostly after chemotherapy. Its diagnosis is clinically relevant but challenging, due to its somewhat inconspicuous histologic features and negative/low expression of classical YSTpt makers (α-fetoprotein (AFP), glypican-3 (GPC3), and GATA3)). HNF1β is likely a key inducer of the YSTpt phenotype, acting in part by regulating the binding of FOXA2 to its target genomic sequences. Recently, immunohistochemical studies have shown that HNF1β has a sensitivity comparable to FOXA2 (higher than GPC3 and AFP) for non-sarcomatoid YSTpt. We found that sarcomatoid YSTpt did not express HNF1β (0: 8/8 (100%)), suggesting that combined downregulation of FOXA2 and HNF1β may underlie the sarcomatoid transformation in this rare phenotype of germ cell tumor.