Schwannomas are neurogenic tumors originating from Schwann cells of a peripheral nerve sheath. They rarely occur in the gastrointestinal tract, with the stomach being the most common location. Gastric schwannomas are normally benign, and malignant transformation, with potential for lymph node metastasis, is extremely rare [4]. The majority of the swollen lymph nodes associated with gastric schwannomas are non-metastatic lymphadenopathy. In this paper, we report the case of a patient with a swollen lymph node of gastric schwannoma diagnosed with FL.
In the present study, the resected tumor histologically showed a peritumoral lymphoid cuff, which is known as a specific morphological finding of schwannoma, present in 78.8%–96.0% of gastric schwannomas [10,11,12]. Hou et al. speculate that the lymphoid cuff may be the result of cytokines secreted by the tumor cells that induce chemokinesis of lymphocytes [13]. This theory is supported by a recent paper; Bae et al. reported that a peritumoral lymphoid cuff of the main tumor positively correlates with the presence and size of regional lymphadenopathy in gastric schwannomas [12]. Regional lymphadenopathy is more commonly noted in gastric schwannomas than in other gastric SMTs [2, 3].
Malignant lymphoma, including FL, is usually noticed by the appearance of B symptoms and/or cervical, axillary, or inguinal swollen lymph nodes [14]. After the imaging test, malignant lymphoma is diagnosed by the excisional biopsy of a cervical, axillary, mesenteric, inguinal, mediastinal, or para-aortic swollen lymph node. Elevation of serum LDH and sIL-2R level, and abnormality of WBC count are helpful for diagnosis. Bulky lymphadenopathy growing around vessels, called the “sandwich sign,” is known as a specific CT feature of the advanced malignant lymphoma [15]. In the present study, FL was coincidentally diagnosed, although there were no B symptoms, blood test abnormality, or significantly swollen lymph nodes on CT.
Primary lesion resection is usually performed for the gastric schwannoma; however, there is no consensus for the operative procedure of gastric schwannoma with swollen lymph nodes. In clinical practice, gastrectomy with lymph node dissection is occasionally performed when swollen lymph nodes are accompanied with gastric schwannomas, due to concern about the possibility of metastasis from the main tumor. However, most cases actually have no pathological lymph node metastasis [5,6,7]. This means that the routine lymph node dissection for the swollen lymph nodes of gastric schwannoma is unnecessary in most cases and can be an excessive invasion. Lymph node dissection is not necessary when the swollen lymph node is either non-metastatic or malignant lymphoma. From a clinical perspective, to avoid excessive invasion, the lymph node’s metastatic potential should be determined prior to nodal dissection. If instant diagnosis of malignant lymphoma can become enabled in the future, we propose that the patients undergo intraoperative pathological diagnosis for swollen lymph nodes of gastric SMTs, including schwannoma. This may make it possible to avoid unnecessary lymph node dissection.
In the present case, the patient was asymptomatic and coincidently presented with Ann Arbor stage I and low-tumor burden FL. The patient received no initial therapy for FL. FL is the most common indolent B-cell non-Hodgkin’s lymphoma, most of which are diagnosed in an advanced stage (Ann Arbor stage III/IV) [14, 16]. Limited stage (Ann Arbor I/II) FL is relatively uncommon; therefore, high-quality evidence for the treatment of limited stage FL is lacking [16]. Previous reports in the United States showed that the initial therapy given for stage I patients was as follows: rituximab plus chemotherapy, 28%; radiation therapy, 27%; observation, 17%; systemic therapy plus radiation therapy, 13%; rituximab monotherapy, 12%; and other, 3% [17]. Selected limited stage patients, such as asymptomatic and low-tumor burden patients, can be candidates for the strategy of a watchful waiting approach [9, 14]. This is consistent with our present case. Advani et al. reported that stage I/II patients who received no initial therapy demonstrated that 63% of patients did not require treatment at a median follow-up of 86 months, and the estimated survival at 10 years was 85% [18]. Friedberg et al. reported that stage I patients managed with no initial therapy did not have a worse progression-free survival than those managed with radiation therapy [17].
The prognosis for an individual FL patient can be estimated by the Follicular Lymphoma International Prognostic Index (FLIPI), which is based on clinical and laboratory findings [9]. Five adverse prognostic factors of FLIPI were selected: age (> 60 years vs ≤ 60 years), Ann Arbor stage (III/IV vs I/II), hemoglobin level (< 12 g/dL vs ≥ 12 g/dL), number of nodal areas (> 4 vs ≤ 4), and serum LDH level (above normal vs normal or below). Three risk groups were defined: low (0–1 adverse factor), intermediate (2 adverse factors), and poor (≥ 3 adverse factors). In our case, one adverse factor (> 60 years) was applicable and the risk group was low. On the other hand, gastric schwannomas are normally benign; even those over 100 mm in size and with a mitotic rate greater than 5/50 HPFs showed no evidence of aggressive behavior [10]. The benign gastric schwannoma rarely recurs after complete surgical resection [19]. In this case, the patient was diagnosed with a gastric schwannoma 80 mm in size with the mitotic count 0 to 1 per 50 HPFs, which was completely resected. Concerning the FL and gastric schwannoma in this case, long-term survival is expected to be good.
As this was a single-patient case report, these findings need to be confirmed by the accumulation of prospective evidence from more patients in multiple institutions. Gastric schwannomas are relatively rare; therefore, the number of patients treated in a single institution is limited. However, the current findings provide important information that can contribute to the development of a treatment strategy for gastric schwannomas accompanied with swollen lymph nodes.
