Isolated Metastasis to Fallopian Tube Mucosa by Low-Grade Appendiceal Mucinous Neoplasm: Report of Two Cases

Isolated metastases from non-gynecological cancers to the fallopian tube are rare. Recent literature suggests that mucosal alterations of the fallopian tube should be considered primary tubal lesions. This has led to a paradigm shift in the classification of ovarian tumors with studies proposing tubal origin for these tumors, and clinicians advocating distal salpingectomy to decrease rates of ovarian cancer. This is based on the theory that sole presence of tubal mucosal disease is evidence of tubal origin. We present two patients with isolated mucosal metastases to the fallopian tube from appendiceal tumors. Two 36- and 72-year-old women presented with adnexal masses. Both had a history of right hemicolectomy for low-grade appendiceal mucinous neoplasms. The tubes in both cases were distended with mucin. Microscopic examination showed multifocal low-grade mucinous epithelium with papillations and tufting, interspersed by normal tubal epithelium. The mucinous epithelium was diffusely positive for keratin 20 and CDX2, focally positive for keratin 7, and negative for ER and PAX8 in both cases. Ovaries showed acellular mucin pools. Based on morphology and immunohistochemical features, it is likely that these tumors are of primary appendiceal origin metastatic to fallopian tube mucosa. These cases are unique in that no other organs were involved by metastases raising the possibility of an in-situ lesion or benign tubal mucinous metaplasia. These cases bring up an important point that mucosal metastasis can occur and question the current practice of assigning primary origin of a tumor to the fallopian tube in the presence of "intraepithelial" tumor.