Sarcoidosis is a systemic disease of unknown cause. It produces epithelioid granulomas in one or several body sites. In patients with other diseases, similar epithelioid granulomas are formed in the affected organ itself and in regional lymph nodes, and the formation of such granulomas is termed a sarcoid reaction [1]. An association between sarcoid reactions and malignancy has been reported several times [2]. Sarcoid reactions occur within the locoregional lymph nodes that drain the cancer. Brincker et al. [1] reported that sarcoid reactions occur in 4.4 % of patients with various cancers, such as skin, lung, ovary, stomach, and breast cancers. However, only a few published reports have described sarcoid reactions in patients with colorectal cancer [3–6]. Furthermore, there are no reports of this reaction in the spleen and regional lymph nodes after colon cancer resection. In the present case, we suspected splenic metastasis while following up our patient for colon cancer. The CT and FDG PET-CT findings were not inconsistent with splenic metastasis. However, it is extremely difficult to differentiate between malignancy and a sarcoid reaction using CT or FDG PET-CT because the tissue involved in the sarcoid reaction accumulates FDG. When a sarcoid reaction occurs in the mediastinal lymph nodes, endoscopic ultrasound with fine-needle aspiration of the lymph nodes is believed to be the best choice for diagnosis [5]. However, the performance of a splenic biopsy to confirm the diagnosis is unrealistic because of the risk of peritoneal dissemination or bleeding. Therefore, when a sarcoid reaction occurs in the spleen, it is almost impossible to distinguish it from metastasis unless a surgical operation is performed. We suspected that the splenic mass was isolated metastasis from colon cancer at first. Splenic metastasis from colorectal cancer is generally a part of systemic disease. Whether to perform splenectomy in patients with isolated splenic metastasis from colorectal cancer is controversial. However, Abi saad et al. [7] reported that splenectomy for isolated splenic metastasis can achieve long-term survival. Furthermore, Jiddou et al. [8] reported 31 cases of isolated splenic metastasis from colorectal cancer, and splenectomy was performed in all cases. In addition, there are reports of laparoscopic approach too [8, 9]. Therefore, we performed laparoscopic splenectomy for the cure of isolated splenic metastasis, and yet histopathological examination of the spleen showed a sarcoid reaction. A sarcoid reaction is a benign tumor itself. When splenic metastasis from colon cancer is suspected, the possibility of a sarcoid reaction should be considered. Minimally invasive surgery such as laparoscopic surgery may therefore be the best option for diagnosis and treatment, as in our case.
The pathogenesis of a tumor-associated sarcoid reaction in the lymph nodes or spleen has not yet been determined. Fujii et al. [4] reported that the possible mechanisms of such a reaction are summarized as follows: (1) a localized defense reaction to the tumor cells themselves, (2) a simple tissue reaction to a tumor embolism in the lymphatic system or capillaries, and (3) an immunological reaction to substances released from the tumors transported along the lymphatic system. Our patient developed a sarcoid reaction in the spleen and regional lymph nodes after adjuvant chemotherapy for colon cancer; moreover, this reaction was recognized in part of liver metastasis by retrospective study. The mechanism of a sarcoid reaction after primary sigmoid colon cancer resection remains a mystery. However, from that, a sarcoid reaction contains in part of liver metastasis; it is speculated that carcinoma cells remaining at the cellular level in the body received some effect by repeated chemotherapy and it showed sarcoid reaction. We concluded that the chemotherapy gave rise to an immunological reaction in our case.
Brincker [1] reported that a sarcoid reaction is most likely caused by antigenic factors against metastatic extension. Pavic et al. [10] suggested that a sarcoid reaction may be associated with a better prognosis in patients with gastric cancer. In another study, however, patients with gastric cancer who developed a sarcoid reaction in both the regional lymph nodes and spleen were more frequently in the advanced stages of disease than were patients with a sarcoid reaction in the regional lymph nodes alone [11]. Even in our case, the sarcoid reaction occurred in both the regional lymph nodes and spleen. Our patient exhibited a new liver metastasis on CT 4 months after the splenectomy. Therefore, we consider that the prognosis of colorectal cancer with a sarcoid reaction in the regional lymph nodes and spleen may be poor, as in patients with gastric cancer. However, to fully determine the relationship between a sarcoid reaction and the prognosis of patients with colorectal cancer, an investigation involving a larger number of cases is required.
In summary, we have reported a rare case of a sarcoid reaction in the spleen and regional lymph nodes. The effect of a sarcoid reaction on the prognosis in patients with colorectal cancer has not been fully determined because of the small number of such cases. Further analyses involving a larger number of cases are necessary to evaluate the relationship between sarcoid reactions and prognosis in patients with colorectal cancer.
