MR Imaging Characteristics And Clinical Pathologic Correlation About Intrapituitary Cystic Degeneration And Fluid-fluid Level Formation

Objectives: This paper aims to explain the MR imaging features and pathologicalmechanisms of the cyst and fluid-fluid level in pituitary adenoma, and to analyze therelationship between it and pathological features, biological behavior, clinical surgeryfeatures, for the sake of improving the level of preoperative imaging assessment, andguideline for surgery and postoperative treatment, as well as the prediction of clinicaloutcome.Methods: Eighty-three pituitary adenomas are collected who are confirmed surgicallyand pathologically, the MR imaging are conducted and the image features of the cystand fluid-fluid level in pituitary adenoma are scrutinized, the relations between theMRI findings and surgical, pathological findings are evaluated, respectively.①TheMRI are obtained using the Siemens3.0-T superconducting magnetic resonancemachine. Three-dimensional magnetic resonance pre-and post-contrast imagings ofpituitary adenomas of all subjects are operated, with plus sweep of the SWI(susceptibility imaging) sequence (axial), DWI(diffusion-weighted imaging) sequence(axial), FLAIR (water suppression imaging) sequence (coronal) in the cystic pituitaryadenomas. All MR images are read commonly by the neurosurgery operator and atleast two physicians or graduate students, and one radiological physician, to conduct adetailed analysis and consistent opinions about tumor size, invasive, cysticdegeneration, with or without fluid levels, the number of fluid levels. Thepreoperative MRI image data analyzed is all within one week and nearest to thesurgery.②All the adenoma-ectomies are operated by the same surgeon. seventy-ninecases are operated by endonasal transspheniodal approach while four cases bytranscranial approach. Tumor color, texture, blood supply, filaments, with or withoutcystic, cyst fluid nature, surrounding tissue boundaries and adhesion, the location of the normal pituitary tissue, tumor invasion to the surrounding circumstances and so onare observated intraoperation, and the tumor resection rate and cerebrospinal fluidleakage are determined.③T he dural biopsy from sellar floor are stained to rate theinvasion by tumor on the light microscope.④The adenomas specimens are stainedwith HE and immunohistochemical indicators such as prolactin (PRL), growthhormone (GH), adrenocorticotropic hormone (ACTH), follicle stimulating hormone(FSH), luteinizing hormone (LH) and Ki-67, and the tumor microvessel density(MVD) are calculated according to CD34immune staining.⑤The complications ofdiabetes insipidus, cerebrospinal fluid leakage, and so on are observed, the MRI areconducted one week and four months after operation.⑥SPSS13.0statistical softwareis used for statistical analysis, P≤0.05as significant level of testing.Results:①According to the preoperative MRI imagings and intraoperative findings,this group of83cases of pituitary adenomas consist of40substantive adenomas,19cases of cystic degeneration but no fluid levels, and24cases with the fluid-fluid levelformation，which accounting for55.8%of the43cases of cystic pituitary adenomas,with12cases a single fluid level,4cases two,8cases more than three fluid levels.The MRI images of cyst without fluid level show oftenly low or slightly low signal inT1WI, high signal in T2WI, while the fluid levels show the MRI imaging features asfollows:19cases a high/low signals on T2WI,4cases high/iso signals,1case low/iso signal; whereas only seven cases found fluid-level on T1WI, which are high/isosignals in4cases, high/slightly hyper2cases, slightly lower/iso signal1case. MRIsignal characteristics of the multiple fluid levels in the same case is essentiallysimilar.②There are two reasons for pituitary cystic degeneration: tumor necrosis,tumor bleeding. The formation of fluid-level mainly owe to the absorption of tumorhemorrhage, or secondary bleeding upon ischemic cystic necrosis. The bleeding maynot be a single factor and may not necessary for level formation in pituitaryadenomas.③Cystic and fluid-level formation are more common in larger, rapidlygrowing, invasive pituitary adenomas, as well as in40to60-year-old, but no genderdifferences. Multiple fluid levels are more often found in giant pituitary adenoma(diameter>4cm), but it is difficult to determine the larger the tumor, the more the number of fluid levels.④Three groups as substantive, cystic but no fluid levels, cystic associated with fluidlevels, the tumor blood supply are rich in17cases (42.5%),13cases (68.4%),16cases(66.7%), respectively. Associated with cystic pituitary adenoma, the tumor bloodsupply is richer, more severe adhesion with the surrounding structure, especially withfluid levels of pituitary adenoma. On surgery, obliged to soft tissue, release of cysticfluid, tumor resection in cystic-pituitary adenoma is relatively easy, but the tumortotally-removed rate is significantly low to the substantive pituitary adenoma (P<0.05)，which is57.89%(11/19) in cystic but no fluid levels,45.83%(11/24) in cysticassociated with fluid levels, while the substantive pituitary adenoma is82.5%(33/40).The incidence of cerebrospinal fluid leakage or postoperative urinary collapsesituation, is no significant difference among the three groups.⑤According to theresults of immunohistochemistry,83cases of pituitary adenoma include16cases ofPRL,6cases of GH,3cases of TSH,28cases of FSH/LH,2cases of ACTH,22cases of non-functional, and6cases of multi-hormonal adenomas. Cystic andfluid-level formation are mainly seen in: PRL, FSH/LH, non-functional, andmulti-hormonal adenomas.⑥The microvascular density (MVD) are14.67±7.70(n=40),13.41±6.90(n=19),10.63±5.49(n=24) in three groups respectively，whichare no significant difference (P>0.05), as well as between functional andnon-functional pituitary adenomas.Conclusions:①Cystic degeneration and fluid-level formation are mainly seen in:PRL, FSH/LH, non-functional, and multi-hormonal adenomas. Larger, rapidlygrowing, invasive pituitary adenoma is inclinated, but it is difficult to determine thegreater tumor, the greater number of the fluid-levels.②Compared to the substantivepituitary adenomas, the substantial part of the cystic pituitary adenomas are soft,easier to remove, but the blood supply are richer, the surrounding adhesions are moreobvious, especially in the fluid-level formed adenomas, thereby, lower tumor removalrate and more inclinately tumor-residual, which might account to postoperativerecurrence. Excessive scraping may increase the risk of cerebrospinal fluid leakage and postoperative diabetes insipidus.③Preoperative MRI assessment about pituitaryadenoma may contribute to the undenstanding of tumor growth pattern and behavior,to the guidance of intraoperative procedures and the clinical prognosis, thepost-treatment.