Two Cases of Uterine Small-cell Neuroendocrine Carcinoma With Somatostatin-receptor-type-2 (SSTR2) Expression and Minor Components of Endocervical Adenocarcinoma.

BACKGROUND/AIM: Uterine small cell neuroendocrine carcinoma (SCNEC) is a highly malignant and aggressive neoplasm. When chemotherapy is necessary, a platinum-based regimen similar to that used for pulmonary SCNEC is recommended. We encountered two cases of uterine SCNEC expressing somatostatin receptor type 2 (SSTR2), both with minor components of endocervical adenocarcinoma (ECAC). This study aimed to clarify the histogenesis and progression of these carcinomas through detailed histopathological, immunohistochemical, and TP53 mutation analysis, in order to contribute to the development of treatment strategies.

CASE REPORT: In both cases, SCNEC components were diffusely positive for synaptophysin and SSTR2, whereas the ECAC components were negative for both markers. Both components were diffusely, block-type positive for p16, suggesting that they were primary cervical cancers of a common origin even if they differed in characteristics and phenotype. In one of the two cases, both SCNEC and ECAC components were diffusely positive for p53. TP53 mutation analysis revealed a shared exon 4 point mutation in both components and an additional exon 7 point mutation only in the SCNEC component, suggesting clonal progression from ECAC to SCNEC.

CONCLUSION: These cases suggest that uterine SCNEC may coexist with, and in some cases arise from, ECAC. SSTR2 expression in uterine SCNEC may have prognostic and therapeutic significance, supporting consideration of somatostatin analogues and future SSTR2-targeted strategies. Because coexisting histological subtypes such as ECAC may persist after treatment directed at SCNEC, therapeutic planning should include careful pathological assessment and consideration of multimodal treatment.