Breast cancer is known to show metastasis highly to liver, bone, lung, pleura, and soft tissue. Metastasis to the gastrointestinal tract or the peritoneum is relatively rare. Regarding correlation between histological type and metastasis site, solid-tubular carcinoma is reported to be highly metastatic to liver and bone, and papillotubular carcinoma and scirrhous carcinoma to the peritoneum [7]. Also, peritoneal dissemination was reported to be more frequent in a case of invasive lobular carcinoma than in a case of invasive ductal carcinoma [8].
Tabei et al. [9] reported that the incidence rate of peritoneal metastasis from advanced and recurrent breast cancer is 3.0%. Mukaiyama et al. [10] reported that the diagnostic rate of metastasis in the gastrointestinal tract or the peritoneum is 6% in living patients, and 31% in autopsy specimens. The higher rate obtained in autopsy specimens maybe due to the fact that candidates for autopsy would be the patients that experienced peritoneal dissemination and metastasis to the gastrointestinal which is often lethal to the patient. Also, it may be the reason why during follow-up of postoperative breast cancer, abdominal examination may not always be highlighted. In terminal clinical condition, in addition to peritoneal metastasis, metastasis to other parenchymal organs, such as lymph nodes, along with lung and liver, were also reported. Since metachronous (late stage) metastasis is more common than synchronous metastases [11, 12], diagnosis of the disease at the first onset is difficult to be made before the operation of the breast cancer [13]. As is with this case, the patient visited the hospital 11 years after the original breast cancer surgery complaining for loss of appetite and a feeling of abdominal distention. In the preoperative imaging test, malignant lymphoma was suspected rather than recurrent breast cancer, due to the long absence of the original disease. The prior preoperative diagnosis made by the attending doctor of internal medicine was malignant lymphoma from the clinical symptoms in need of exploratory laparotomy for final diagnosis. Peritoneal metastasis from the breast cancer could be diagnosed only by the pathological results obtained by the resected sample at the exploratory laparotomy.
Since the patient had loss of appetite and compression of the duodenum was found in the preoperative CT scan, ileus was expected to occur sooner or later. An exploratory laparotomy was first performed for diagnosis. As a result, peritoneal dissemination due to metastasis of breast cancer was diagnosed. Although in additive from the postoperational examinations metastases in vital organs, namely pleural metastasis, were observed, endocrine therapy was selected, which was the primary choice used for the treatment of luminal A like type breast cancer [14]. A single agent oral aromatase inhibitor, letrozole was chosen, considering the background and age of the patient. Chemotherapy was also a choice for vital organ relapse of breast cancer patients, but the adverse effects were determined to be lethal for this particular patient. Recently, endocrine therapy along with the addition of cyclin-dependent kinase4/6(CDK4/6) inhibitors have been reported very promising results [15]. This agent would definitely be a candidate, but the availability was still not possible at the time. Still the chosen single agent endocrine therapy was successful, and after 2 years of continuous treatment, findings of metastasis were not observed by imaging and values of tumor marker were normalized. Although more than 6 years have passed since the onset of recurrence, no evidence of further recurrence has been observed. The patient is no longer receiving active therapy against metastatic breast cancer due to onset of dementia, but her survival was accounted for more than 8 years after the metastatic recurrence of peritoneal dissemination of the breast cancer.
McLemore et al. [3] reported that the median overall survival time of patients with peritoneal metastasis was 14–26 months, while a median survival period of 7 months has been reported by Chu et al. [1]. On the other hand, the average life expectancy was approx. 18 months, and the 5-year survival rate was 13% in patients with stage IV breast cancer [16]. Prognosis for peritoneal metastasis is considered lower than other cases of stage IV breast cancer. In the recent years, however, long-term survival cases have also been reported [17,18,19].
Recently, there are some reports on treatments which have achieved long-term survival in patients with peritoneal carcinomatosis of breast cancer, but detailed treatment outcomes have not been reported. For this reason, a standard therapy has not been established. However, the appropriate treatment for breast cancer as the primary disease is basically applied, namely, multidisciplinary therapy (operation, chemotherapy, endocrine therapy, and molecular targeted drug) [20].
Recent developments in diagnostic technology and treatment methods, such as chemotherapy have achieved a drastic improvement in the prognosis of breast cancer. Hence, along with an improved survival rate of breast cancer, the number of cases with late recurrent carcinomatous peritonitis, even after 11 years as in this case, may also increase. Late recurrence of peritoneal metastasis should be considered when diagnosing patients with a history of breast cancer. There are few reports on peritoneal metastasis from breast cancer, and no standard therapy has been established. Further accumulation of clinical cases and consideration of effective treatment based on these cases are expected.