The current study was performed retrospectively. The sample size can be estimated according to the following formula: n=Z² × [P × (1-P)]/E², where n is the sample size, Z is the statistical value and E is the error. When the confidence is 95%, Z=1.96; P represents the incidence of PPBS- in the normal population, which is 4.1% according to the latest literature (19). E was set to 10% in the current study. RCC patients from January 1st 2010 to January 1st 2016 were enrolled in this retrospective study. All patients underwent RCC resection of the sellar region using the transsphenoidal approach.

The inclusion criteria for the current study were as follows: i) Patients pathologically diagnosed with RCC without sellar region involvement or primary endocrine diseases (such as primary hyperthyroidism and Cushing's disease caused by adrenal tumors); ii) patients did not receive radiotherapy or chemotherapy; iii) patients received surgery that was performed by the same surgeon; iv) patients had complete pre-operative and post-operative MRI data. Patients were excluded if treatment was discontinued or if they did not attend follow-up after surgery. Written informed consent was obtained from every patient, or their legal guardian and the study was approved by the Ethics Review Board of Fujian Medical University.

Patients received pituitary plain and enhanced MRI scans using the Siemens 3.0T (Siemens AG). T1WI (axial and sagittal) and T2WI (the axial and coronal) scans were subsequently performed. The following parameters were used for acquisition of T1WI: TSE (turbo spin echo) sequence, TR (time of repetiton)=400–500 millisec, TE (echo time)=8–15 millisec, 3 stimulations. The following parameters were used for acquisition of T2WI: TSE sequence, TR=3000 millisec, TE=83–98 millisec, 2 stimulations. The scanning field of view was 180×180 mm; matrices were 320–384×240-252; the thickness of the axial scanning layer was 3.0 mm and the layer distance was 3.0 mm; the thickness of the coronal and sagittal layer was 2.5 mm and the layer distance was 2.5 mm. Three-dimensional enhanced MRI scanning was then performed. Gd-DTPA (gadolinium-diethylenetriaminepentaacetate) was used at dose of 0.2 mmol/kg body weight and the scanning parameters were the same as the aforementioned scan.

Pre-operative MRI scans were reviewed by a professor of neurosurgery, an associate professor of neurosurgery and an associate professor of radiology from Fuzhou General Hospital. A consensus was reached among the physicians on all diagnoses. The MRI images at 1 week before and after the operation were analyzed. The following parameters were assessed: i) Location and size of RCC: The RCC was observed on MRI-T1WI sagittal, T2WI sagittal and enhanced T1WI sagittal. The line connecting the tuberculum sellae and the dorsum sellae was used as a reference to classify the RCCs as intrasellar, intrasellar-suprasellar or purely suprasellar. In the INFINITT PACS Medical Imaging System (syngo.via software VB10; Siemens Healthineers), the maximum diameter was used to determine the RCC size. Lesions with diameter <10 mm were considered small RCCs and lesions with a diameter ≥10 mm were considered large RCCs. ii) MRI signal and intracystic nodules in the RCC: The RCC signal was observed using both the MRI-T1WI and MRI-T2WI sequence. The nodules in the RCC (nodule number, position, size and signal characteristics) were observed under multiple MRI sequences. iii) PPBS presentations: PPBS was observed under sagittal MRI-T1WI and defined as PPBS positive (+) and PPBS negative (−).

Patients were placed into a supine position with a neck extension of 15–20°. The right nasal approach was selected and a nasal septum incision was performed under a surgical microscope. The nasal septum mucosa was retracted and the nasal septum bone was pushed to the left side. The surgical corridor was achieved between the right mucosal membrane lining nasal septum and ethmoid vertical plate to the front of the sphenoid sinus using a nasal speculum. A grinding drill was used to remove the anterior wall of the sphenoid sinus and the sellar face, and the sellar dura was opened in an ‘X’ or ‘T’ shape. A circular scraper, tumor tweezers and an aspirator were used to gradually remove cyst tissue, using minimal force to strip the cyst wall. When the resection was satisfactory, the lesion bed was washed repeatedly.

The histopathological features of 31 RCC specimens were observed. The specimens were fixed in 10% neutral formalin solution at room temperature for 12 h, sliced (3 µm) and paraffin embedded before staining with hematoxylin and eosin (H&E) at room temperature for 5 min for each stain. Examinations were performed under a light microscope (BX51; Olympus Corporation), including analyzing the type and the extent of fibrosis of the wall epithelium, as well as the presence of inflammatory infiltrates. The number of inflammatory cells (including neutrophils, lymphocytes and macrophages) in the slide with the largest extent of infiltration was counted. Inflammation was defined as ≥10 inflammatory cells/5 fields (magnification, ×100) and <10 inflammatory cells/5 fields was determined to be negative for inflammation (magnification, ×100).

Data were analyzed using SPSS 16.0 statistical software (SPSS, Inc.). Quantitative data were expressed as the mean ± standard deviation. Categorical data was expressed as a percentage and analyzed using χ² tests (including the Fisher's exactness test). Measurement data (including age and cyst size) were tested for normality and were compared using independent t-tests. P<0.05 was considered to indicate a statistically significant difference.

A total of 45 cases were included in the current study, including 15 males and 30 females. The average age was 43.18±14.08 years, ranging from 13–68 years. Among the 45 cases, 18 had pre-operative headache (40.00%), 13 experienced dizziness (28.89%), 12 demonstrated visual impairment (26.67%), 3 had polydipsia (6.67%), 1 was going through menopause (2.22%), 1 was lactating (2.22%), 3 experienced fatigue (6.67%) and 8 had no symptoms, but were diagnosed based on the result of their annual medical imaging examination (17.78%). Cyst diameter ranged from 5.60–25.47 mm (mean, 13.80±4.99 mm). No cases of multiple RCCs were observed.

RCC features were analyzed using MRI. There were 12 intrasellar RCC cases, 33 intrasellar-suprasellar cases and no purely suprasellar cases. A total of 12 cases were classified as small RCC and 33 cases were classified as large RCC. MRI-T1WI revealed 18 cases with an isointense signal, 16 cases with a hyperintense signal, 9 cases with a hypointense signal, 1 case with a heterogeneous signal and 1 case with a stratification effect [where the upper part of the RCC had an isointense signal (long arrow) and the lower part had a hyperintense signal (short arrow), with a clear border between them; Fig. 1A]. MRI-T2WI identified 5 cases with an isointense signal, 27 cases with a hyperintense signal, 11 cases with a hypointense signal, 1 case with a heterogeneous signals and 1 case of stratification (isointense signal, long arrow; hyperintense signal, short arrow; Fig. 1B).

Of the 45 cases, 20 exhibited intracystic nodules in T1WI, T2WI and T1 contrast enhanced sequences, as presented in Table I and Fig. 2. The range in nodule diameter was 1.67–9.76 (5.19±2.57) mm and the corresponding RCC diameter was 7.06–20.12 (12.65±3.07) mm, with the figures in brackets presenting the mean ± standard deviation. Of the intracystic nodules of RCCs, 3 cases exhibited hyperintense signals on T1WI, 5 cases had hypointense signals on T1WI, 13 cases had hypointense signals on T2WI, 4 cases had hypointense signal in the enhanced sequence and 2 cases had multiple nodules (as indicated by white arrows in Fig. 2F and G). There were no nodules with hyperintense signals on T2WI. The nodules were mostly of a round shape; however some displayed oval and irregular shapes and 1 case exhibited concentric rings (indicated by a white arrow in Fig. 2H). Three cases displayed intracystic nodules adherent to the cyst wall and the intracystic nodules in 17 cases were non-adherent. Several intracystic nodules were located at the center of the RCC (as indicated by white arrows in Fig. 2E and H), or in the lower, posterior or anterior parts of the RCC (as indicated by white arrows in Fig. 2A-D, F and G). These results indicated that RCCs have various signal intensities on MRI and that intracystic nodules also have various shapes and signal intensities on MRI. It is worth noting that the nodules observed through MRI were not always identified during surgery. This implies that some of the observed nodules could be real or could be artifact created by the MRI (Fig. 3A-H).

To determine the PPBS positive incidence in RCC patients, the MRI-T1WI of the 45 RCC patients were analyzed. Among the 45 RCC cases, PPBS was identified in only 10 cases. PPBS appeared in linear, triangular, crescent and bilinear shapes in the sagittal view and were located at the posterior part of the sella turcica, in contact with the dorsum sellae (Fig. 4A-F). These results indicated that the incidence of positive PPBS in RCC patients was low.

To observe the histopathological features of RCC, H&E staining was performed. Among the 31 pathological specimens, 12 cases exhibited cyst wall epithelium, including 4 cases of monolayer cube epithelium (as indicated by the white arrow in Fig. 5A), 7 cases displayed pseudostratified ciliated columnar epithelium and 1 case displayed ciliated columnar epithelium and squamous metaplasia (as indicated by the white arrows in Fig. 5B). Of the 25 cases with cyst content, 17 cases presented pink staining on H&E, 4 cases exhibited blue staining (as indicated by the white arrow in Fig. 5C) and 4 cases had both pink and blue staining (Fig. 5D). The arrows in Fig. 5D indicate inflammatory cell infiltrates (mainly mononuclear cells). In the tissue sections of RCC specimens with blue staining, the contents of the cysts were diverse. The size and coloration of protein bodies were highly variable and some even exhibited hyaline degeneration. No cholesterol crystals were identified. A total of 14 cases displayed inflammatory responses (Fig. 5E). The arrows in Fig. 5E show numerous pink stained protein globules in the cyst fluid. There were numerous lymphoid cells and some eosinophils in the anterior pituitary gland.

According to the presence of PPBS on MRI, patients were divided into the PPBS+ group (n=10) and the PPBS- group (n=35). The differences in age, sex, RCC location and size of cysts between the two groups were analyzed. As presented in Table II, of the 45 RCC cases, there were 15 males with 2 cases of PPBS+ and 13 cases of PPBS-. Of the 30 female cases, 8 cases of PPBS+ and 24 cases of PPBS- were identified. No significant differences were identified between the sex of the PPBS+ and PPBS- patients. In the PPBS+ and PPBS- groups, the average ages were 42.00±16.65 years and 43.51±13.51 years, respectively. No significant differences between the ages of the two groups were identified. Similarly, there were no significant differences in RCC location or size of cysts between the two groups. These results suggested that the presence of PPBS was not associated with sex, age, RCC size or RCC location.

The relationship between PPBS status and the inflammatory response was analyzed. Among the 31 patients with histopathological specimens, 10 had PPBS+. Among the 10 cases with PPBS+, 2 (20%) had inflammatory responses. There were 21 cases of PPBS- and among them, 14 (66.7%) had inflammatory responses. The PPBS+ cases had significantly lower inflammatory responses than the PPBS- cases (P<0.05; Table III). Thus, the data demonstrated that the inflammatory response may be associated with the presence of PPBS.