SWI/SNF protein and claudin‐4 expression in anaplastic carcinomas arising in mucinous tumours of the ovary and retroperitoneum.

Aims: Anaplastic carcinoma arising in a mucinous tumour of the ovary and rarely in the retroperitoneum is an uncommon neoplasm with three morphological patterns; rhabdoid, sarcomatoid and pleomorphic. We investigated expression of switch/sucrose non‐fermentable (SWI/SNF) chromatin remodelling complex components and claudin‐4 expression. Methods and results: Twenty‐two ovarian and three retroperitoneal mucinous tumours were investigated using antibodies against SMARCB1, SMARCA4, SMARCA2, ARID1A and claudin‐4. Loss of nuclear staining for any SWI/SNF protein was observed in the anaplastic component of nine of 25 (36%), with retained expression within the mucinous component of all tumours. Five (56%) showed loss of more than one protein, with dual loss of SMARCA4 and SMARCA2 in two, loss of SMARCA2 and ARID1A in two and loss of SMARCB1 and SMARCA2 in one. Retained expression of claudin‐4 was seen in 39% of the anaplastic carcinomas and within the mucinous component of all tumours. Rhabdoid morphology was associated with poor prognosis [stages III or IV disease (six of six, 100% versus four of 14, 29%; P = 0.0108] and death from disease (three of four, 75% versus one of 13, 8%; P = 0.0223). Although loss of a SWI/SNF protein was not significantly associated with death from disease (three of five, 60% versus one of 12, 8%; P = 0.0525), it showed a trend in correlation with poor prognosis and was often noted in tumours with rhabdoid morphology within this small cohort. Conclusions: Our report adds to the growing list of female genital tract malignancies with loss of SWI/SNF proteins, underlining their broad differential diagnosis and the importance of careful, context‐dependent interpretation of SWI/SNF protein loss. [ABSTRACT FROM AUTHOR]