Insulinoma and Tuberous Sclerosis: A Possible Mechanistic Target of Rapamycin (mTOR) Pathway Abnormality?

Malignant tumors in tuberous sclerosis complex: a case report and review of the literature

BACKGROUND

Tuberous sclerosis complex (TSC) is a rare, autosomal dominant genetic disease that arises from TSC1 or TSC2 genetic mutations. These genetic mutations can induce the development of benign tumors in any organ system with significant clinical implications in morbidity and mortality. In rare instances, patients with TSC can have malignant tumors, including renal cell carcinoma (RCC) and pancreatic neuroendocrine tumor (PNET). It is considered a hereditary renal cancer syndrome despite the low incidence of RCC in TSC patients. TSC is typically diagnosed in prenatal and pediatric patients and frequently associated with neurocognitive disorders and seizures, which are often experienced early in life. However, penetrance and expressivity of TSC mutations are highly variable. Herein, we present a case report, with associated literature, to highlight that there exist undiagnosed adult patients with less penetrant features, whose clinical presentation may contain non-classical signs and symptoms, who have pathogenic TSC mutations.

CASE PRESENTATION

A 31-year-old female with past medical history of leiomyomas status post myomectomy presented to the emergency department for a hemorrhagic adnexal cyst. Imaging incidentally identified a renal mass suspicious for RCC. Out of concern for hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome, the mass was surgically removed and confirmed as RCC. Discussion with medical genetics ascertained a family history of kidney cancer and nephrectomy procedures and a patient history of ungual fibromas on the toes. Genetic testing for hereditary kidney cancer revealed a 5'UTR deletion in the TSC1 gene, leading to a diagnosis of TSC. Following the diagnosis, dermatology found benign skin findings consistent with TSC. About six months after the incidental finding of RCC, a PNET in the pancreatic body/tail was incidentally found on chest CT imaging, which was removed and determined to be a well-differentiated PNET. Later, a brain MRI revealed two small cortical tubers, one in each frontal lobe, that were asymptomatic; the patient's history and family history did not contain seizures or learning delays. The patient presently shows no evidence of recurrence or metastatic disease, and no additional malignant tumors have been identified.

CONCLUSIONS

To our knowledge, this is the first report in the literature of a TSC patient without a history of neurocognitive disorders with RCC and PNET, both independently rare occurrences in TSC. The patient had a strong family history of renal disease, including RCC, and had several other clinical manifestations of TSC, including skin and brain findings. The incidental finding and surgical removal of RCC prompted the genetic evaluation and diagnosis of TSC, leading to a comparably late diagnosis for this patient. Reporting the broad spectrum of disease for TSC, including more malignant phenotypes such as the one seen in our patient, can help healthcare providers better identify patients who need genetic evaluation and additional medical care.

Approach to the Patient: Insulinoma

Insulinomas are hormone-producing pancreatic neuroendocrine neoplasms with an estimated incidence of 1 to 4 cases per million per year. Extrapancreatic insulinomas are extremely rare. Most insulinomas present with the Whipple triad: (1) symptoms, signs, or both consistent with hypoglycemia; (2) a low plasma glucose measured at the time of the symptoms and signs; and (3) relief of symptoms and signs when the glucose is raised to normal. Nonmetastatic insulinomas are nowadays referred to as "indolent" and metastatic insulinomas as "aggressive." The 5-year survival of patients with an indolent insulinoma has been reported to be 94% to 100%; for patients with an aggressive insulinoma, this amounts to 24% to 67%. Five percent to 10% of insulinomas are associated with the multiple endocrine neoplasia type 1 syndrome. Localization of the insulinoma and exclusion or confirmation of metastatic disease by computed tomography is followed by endoscopic ultrasound or magnetic resonance imaging for indolent, localized insulinomas. Glucagon-like peptide 1 receptor positron emission tomography/computed tomography or positron emission tomography/magnetic resonance imaging is a highly sensitive localization technique for seemingly occult, indolent, localized insulinomas. Supportive measures and somatostatin receptor ligands can be used for to control hypoglycemia. For single solitary insulinomas, curative surgical excision remains the treatment of choice. In aggressive malignant cases, debulking procedures, somatostatin receptor ligands, peptide receptor radionuclide therapy, everolimus, sunitinib, and cytotoxic chemotherapy can be valuable options.

Insulinoma in pediatric tuberous sclerosis complex: a case report

Background

Tuberous sclerosis complex (TSC) is a rare multisystemic disorder. This genetically determined disease is characterized by highly variable clinical expression, including epilepsy as a common feature. Seizures can also occur as a manifestation of symptomatic hypoglycemia. The latter could be caused by an insulinoma, whose association to TSC has already been debated. In TSC-associated tumors, dysregulation of the mTOR pathway is believed to be present, leading to significant impacts on cellular metabolism, growht, and proliferation. To date, the association between TSC and insulinoma has been reported in 11 adults. Here, we present the first case of a pediatric patient with TSC diagnosed with an insulinoma and review the existing literature on this topic.

Case presentation

A 11-year-old female with TSC presented with seizures unresponsive to standard therapy. Further investigation revealed that these seizures were caused by hypoglycemia. Subsequent evaluation led to the diagnosis of a pancreatic insulinoma, which was surgically removed. Following the procedure, the patient was free from seizures.

Conclusions

In individuals with TSC, the recurrence of epileptiform episodes throughout their lifetime, especially if previously well controlled with antiepileptic therapy, should raise suspicion for hypoglycemic events. These events may potentially be associated with the presence of an insulinoma. Further research and increased awareness are necessary to gain a better understanding of the association between TSC and insulinomas, and to guide clinical management strategies.

IS THERE A RELATIONSHIP BETWEEN TUBEROUS SCLEROSIS COMPLEX AND INSULINOMA?

Tuberous sclerosis complex (TSC) is an inherited neurocutaneous disease characterized by multiple hamartomas in multiple organs. However, there is limited evidence about neuroendocrine tumors (NETs) in patients with TSC, and routine screening of NETs is not recommended in the guidelines. Insulinomas are also an extremely rare disease. According to our knowledge, we presented the 10th TSC patient diagnosed with insulinoma in the literature. Thirty-two years old male patient diagnosed with TSC at the age of 27 due to typical skin findings, renal angiomyolipoma, history of infantile seizures, and cranial involvement was referred to our clinic. The main symptoms of the patient were palpitations, diaphoresis, confusion, and symptoms were improved after consuming sugary foods. Seventy-two hours fasting test was performed, and a low glucose level at 41 mg/dl, a high insülin level at 21.65 µIU/mL, and a high C-peptide level at 7.04 ng/mL were found at the 8th hour. In addition, a 12x7 mm lesion in the pancreatic tail was detected in abdominal imaging. Ga-68 PET-CT (gallium-68 positron emission tomography-computed tomography) detected an increased uptake of Ga-68 in the pancreatic tail. The patient underwent distal pancreatectomy, and pathological evaluation was consistent with an insulinoma. The patient's symptoms improved postoperatively. Since in nearly all TSC cases, as in our case, neuropsychiatric abnormalities, such as epilepsy, are one of the main disease manifestations, and these symptoms may be confused with the clinical manifestations of hypoglycemia in insulinoma. Therefore, patients with newly developed neurological symptoms and behavioral defects should be evaluated in terms of insulinoma.

Insulinoma in tuberous sclerosis: An entity not to be missed

Pancreatic neuroendocrine tumors are rare with an incident rate of 5 cases per million individuals. Tuberous sclerosis complex is an autosomal dominant disease. This disease involves multisystem and occurs in one out of every 6,000-10,000 individuals. In this study, we describe a 47-year-old male known tuberous sclerosis patient with an insulinoma. The tumor was incidentally detected in follow-up imaging for a previous ampulla of Vater tubular adenoma. However, the patient reported symptoms of hypoglycemia. The insulinoma was enucleated successfully. Histopathology revealed a well-differentiated, grade one neuroendocrine tumor measuring around 2 cm in diameter. Seven cases were reported in the literature of tuberous sclerosis-associated insulinoma. The 7 reported cases had different hypoglycemia related symptoms. The reported tumors varied in size and location on the pancreas. This paper details the eighth case worldwide where an insulinoma occurred in a tuberous sclerosis patient.