Expanding the morphological spectrum of ovarian microcystic stromal tumour

Abstract

Aims To expand the morphological spectrum of ovarian microcystic stromal tumour, a rare neoplasm considered to have a relatively constant morphology with microcysts, solid cellular regions and hyalinised fibrous stroma. Methods and results We report four ovarian neoplasms in patients aged 45, 56, 61 and 71 years with the characteristic immunophenotype of microcystic stromal tumour (diffuse nuclear positivity with beta‐catenin, cyclin D1 and WT1; diffuse cytoplasmic positivity with CD10; negative inhibin, calretinin, oestrogen receptor and progesterone receptor). The tumours had variant morphology (diffuse, nested and corded arrangements in three cases, including one with spindle cell elements; nested, corded and tubular in the other). A CTNNB1 point mutation in exon 3 (c.98C>G,p.S33C; c.100G>A,p.G34R; c.97T>G,p.S33A) was present in the three cases with material available for testing. Conclusions We feel that the cases we report are related to microcystic stromal tumour but with variant morphology; as such, the morphological spectrum of ovarian microcystic stromal tumour is broader than hitherto reported.

Practical roles for molecular diagnostic testing in ovarian adult granulosa cell tumour, Sertoli–Leydig cell tumour, microcystic stromal tumour and their mimics

“…A somatic mutation of CTNNB1 exon 3 has been reported in 73% (22/30) of MCSTs . The mutation was missense in all but one case, which was a deletion mutation .…”

“…Sanger sequencing or targeted NGS of exon 3 (Figure C) is the mainstay of CTNNB1 mutation testing. In the specific setting of MCST, immunohistochemical testing for nuclear expression of β‐catenin appears to be a reasonable surrogate for mutation testing; the presence of nuclear staining in MCSTs is associated with CTNNB1 mutation in approximately three‐quarters of cases, and nearly all MCSTs with CTNNB1 mutation show β‐catenin nuclear staining …”

“…As CD10 is typically diffusely expressed in MCST but not in these other tumours, it may be used as a companion to β‐catenin staining. Cyclin D1 and androgen receptor are also expressed in MCST . CTNNB1 mutation testing is not necessary if the immunostain is used, as mutation is present in just over half of MCSTs, whereas nearly all MCSTs show nuclear staining of β‐catenin.…”

“…Recently, morphological variants of MCST with solid nested and corded growth have been reported . It is possible that such patterns may raise consideration of solid pattern endometrioid carcinoma of the ovary, either primary or metastatic from the endometrium.…”

“…Cyclin D1 and androgen receptor are also expressed in MCST. 65 CTNNB1 mutation testing is not necessary if the immunostain is used, as mutation is present in just over half of MCSTs, whereas nearly all MCSTs show nuclear staining of b-catenin.…”