GH-Producing pituitary adenoma and concomitant Rathke's cleft cyst: A case report

INTRODUCTION: Rathke cleft cysts (RCCs) are commonly believed to be cysts formed from remnants of Rathke's pouch. It is usually asymptomatic, < 3mm in diameter, and found in 13–33% of normal pituitary glands. The coexistence of pituitary adenoma (PA) and RCC is rare (incidence rate of 0.51%-1.7%), and growth hormone hypersecretion has also been observed in a limited number of cases in these patients. Therefore, we aim to present a rare case of growth hormone- (GH-) producing PA with concomitant RCC. CLINICAL CASE: A 29-year-old female patient, due to primary amenorrhea, was diagnosed as having 46XY chromosomal Swyer syndrome from her previous visit, and she had bilateral salphengoopherectomy afterward. In clinical follow-ups, due to the presence of growth complaints in the hands and feet, insulin-like growth factor-1 (IGF-1) was found to be high. The basal serum GH value was 8.89 ng/mL, and IGF-1 was 369 ng/mL. The 75 gr oral glucose tolerance test (OGTT) result showed that the serum GH level was not suppressed below 1.0 μg/L, and the test was repeated twice. Other anterior pituitary hormone axes are normal. In the pituitary magnetic resonance imaging revealed a low-signal 4 mm Rathke cleft cyst is observed in the T1A image in the midsection of the pituitary gland and a high-signal intra-cystic nodule is observed within the cyst on the T1A image (Figure 1A). The fluid-fluid level is observed in the cyst on the T2A image (Figure 1B). [Figure: see text] CONCLUSION: The relationship between RCC and PA is unclear and theoretical. The theory is “transitional pituitary tumor,” defined as the Rathke pouch forming the anterior lobe of the pituitary gland with a proliferation of the anterior wall. Moreover, PAs originate from the anterior lobe of the pituitary gland via clonal changes. This shows that RCCs originated from the remnant of the Rathke pouch, and PA has a common embryonic origin. Nevertheless, they rarely occur at the same time. Only 14 patients with GH-producing PA and concomitant RCC have been reported in the literature. Preoperative correct diagnosis of PA and RCC coexistence is difficult, because RCCs’ imaging characteristics (size, position, and intensity) are highly variable, and cystic degeneration occurs in 5% to 18% of PA cases. RCCs are often surrounded by the normal pituitary gland and are located in the nearby midline of the sellar region. MRI characteristics of sellar lesions for PAs existing concomitant with RCCs may present with variable intensity on T1-weighted imaging. If radiographic imaging shows that typical RCC and PA are not obvious at first glance, the possibility of concomitant PA still needs to be considered. If the PA in this patient had been nonfunctional, correct diagnosis of the concomitant PA would have been much more difficult. This case offers a reminder that although rare, RCC can accompany PA, and performing contrast-enhanced MRI is useful to detect RCC.