Splenic cord capillary hemangioma is classified as splenic hamartoma, which is a rare benign vascular lesion with an incidence of three cases in 200,000 splenectomies [4]. Krishnan proposed a classification of splenic hamartomas based on the relative proportion of the various red pulp elements [2] – classic hamartoma and three variant forms: cord capillary hemangioma, myoid angioendothelioma, and the histocyte-rich variant. Immunohistochemically, splenic cord capillary hemangioma is characterized by predominance of CD8 negative, CD31 positive, CD34 positive cord capillary and with few sinuses. We searched cases thought to be splenic cord capillary hemangiomas by PubMed using key words “spleen,” “cord capillary hemangioma,” or “splenic cord capillary hemangioma.” Only a few citations in English were evident. There appear to be few reports about splenic cord capillary hemangioma, although in recent years, over 100 of cases of splenic hamartomas have been published. This situation might have arisen because immunohistochemical studies are needed to precisely classify the types of splenic hamartoma. In 2015, Tajima et al. [1] mentioned that, when strictly defined, there were eight cases of splenic cord capillary hemangioma that were reported before them. After the report, there was only one report about splenic cord capillary hemangioma. Of all the 10 cases documented to date including our case, we were able to obtain 4 cases of clinical courses in detail because 7 cases reported by Chiu et al. [5] had no clinical courses. We have summarized the previous four case reports about splenic cord capillary hemangioma in Table 1.
Table 1 Clinical features of four cases of splenic cord capillary hemangioma Generally, it is difficult to find small splenic tumors because there are usually no specific symptoms when the tumor is tiny. However, with its growth or progression, the patient may notice an abdominal mass and experience abdominal distension, back pain, dyspnea, and constipation. Some patients have experienced nontraumatic rupture of the spleen and hypersplenism, such as thrombocytopenia and anemia, even though the splenic cord capillary hemangioma showed no specific symptoms [2]. In our present case, the tumor was detected in its very early stage because the patient received a thorough examination in our effort to resolve his hypoglycemia-related symptoms and indeed not due to symptoms of the tumor’s progression or growth.
Hypoglycemia can be induced by tumors, including pancreatic tumors that secrete insulin, and also by non-islet cell tumors that secrete IGFs. Therefore, in the absence of insulinoma, NICTH should be considered. NICTH is thought to be related to the production and secretion of IGF-II by the tumor [3]. NICTH is one of the causes of spontaneous hypoglycemia. In some cases, patients experience severe hypoglycemia, and intensive treatments such as continuous glucose injections are needed. One of the mechanisms of NICTH is thought to be an excessive production of the high molecular weight form of IGF-II by tumors [3, 8]. In cases of NICTH, it is thought that within tumor cells, the enzymatic processing of pro IGF-II into mature IGF-II is somehow not performed normally. Therefore, tumors secrete incompletely processed pro IGF-II as a high molecular weight form of IGF-II [8].
Most commonly, NICTH has been observed in patients with solid tumors that have either a mesenchymal origin, like fibrosarcoma, fibroma, and mesothelioma, or which have an epithelial origin, such as hepatocellular carcinoma and adrenocortical carcinoma. These tumors are frequently quite large at the time of diagnosis. About 70% of them have been greater than 10 cm in diameter [9]. In our present case, the patient fortunately experienced hypoglycemia-related symptoms that were relatively mild and temporary. This might have been because the size of the tumor was smaller than tumors reported before.
One of the limitations of this case report is that we did not detect the production of the high molecular weight form of IGF-II in his serum, and therefore, it was not certain whether this NICTH case was related to the high molecular weight form of IGF-II. In this particular case, this NICTH might have been related to the high molecular weight form of IGF-II since serum growth hormone and plasma cortisol were relatively low (GH 0.15 ng/mL (< 1.46 ng/mL) and the cortisol level was 16.6 μg/dL (4.0–23.3 μg/dL) [8]. Moreover, we confirmed the presence of IGF-II-positive cells in the tumor by an additional immunohistochemistry. To the best of our knowledge, there has not previously been a report in the literature about a case of splenic cord capillary hemangioma with NICTH.