[HER2 amplification and PD-L1 expression in invasive stratified mucin-producing carcinoma of the cervix: a clinicopathological analysis of eighteen cases].

Objective: To investigate the clinicopathological features, prognosis and the expression of HER2 and PD-L1 in invasive stratified mucin-producing carcinoma of the cervix (ISMC). Methods: The clinicopathological data of 18 ISMC cases with radical resection of the cervix diagnosed in the Daping Hospital, Army Medical University from January 2018 to December 2023 were collected and retrospectively analyzed. PD-L1 and HER2 immunohistochemical staining and HER2 FISH were conducted. Results: The patient ages ranged from 31 to 72 years, with an average of 45 years. Approximately 8% of cervical adenocarcinoma cases in our hospital during the same period. Eleven cases were pure ISMC, and 7 cases were mixed-type ISMC, with the component of squamous cell carcinoma or usual-type adenocarcinoma. One case showed concurrent small cell neuroendocrine carcinoma (SCNEC). Three cases were diagnosed through biopsy (3/18). Five cases were of Silva pattern B and 13 cases of Silva pattern C. Three cases showed regional lymph node metastasis. Thirteen patients were disease-free at the end of the follow-up, while the ISMC patient with concurrent SCNEC developed distant metastasis. Fifteen cases (15/18) had PD-L1 expression with CPS≥1, and 7 cases (7/18) had PD-L1 TPS≥1%. One case of HER2 3+ and one case of HER2 2+ were both positive for FISH amplification; two cases HER2 1+, 14 cases HER2 0. Conclusions: Cervical ISMC is rare, has a wide spectrum of morphology, and can coexist with other types of cervical cancer. PD-L1 is positive in most of the ISMC cases, while HER2 is amplified or lowly expressed in a small portion of them. Thus, it is possible to treat ISMC patients with therapies targeting PD-L1 and therapy targeting HER2.