Magnetic resonance imaging grading of pituitary macroadenoma - SIPAP classification revisited

Abstract

Background: Magnetic resonance imaging (MRI) is regarded as the modality of choice in diagnosis of pituitary macroadenomas. Since surgery is the first line therapy for all pituitary adenomas, simple and reproducible MRI classification based on major directions of tumour growth is an essential tool. SIPAP MRI classification for pituitary adenoma describes tumor extension in parasellar, suprasellar, infrasellar, anterior and posterior directions. We, therefore, evaluated reproducibility of SIPAP classification in reporting of pituitary adenomas.

Methods: Forty-nine patients with biopsy-proven pituitary macroadenoma were graded according to SIPAP classification. Data was analyzed using Stata version 15. Interobserver variability was calculated using Cohen's Kappa. Comparison between grading before and after treatment was performed by Chi-square test. P values < 0.05 were considered statistically significant.

Results: Individual tumour extensions according to SIPAP for pre- and post-operative grading showed significant difference (p-value <0.001), except for anterior extension. For suprasellar extension, 67.3 % patients had pre-operative grade-3 and 63.3 % had post-operative grade-0. For infrasellar extension, 51.0 % had pre-operative grade-2 and 71.4 % had post-operative grade-0. Anterior, posterior and parasellar extensions showed increased frequency in grade-0 in post-operative stage compared to pre-operative. Substantial inter-observer agreement was achieved for Superior, Inferior, Anterior and Posterior extent with all Kappa statistics values above 0.7 (p-value <0.001).

Conclusion: We propose incorporating simple and objective SIPAP classification in routine MR reporting for ideal pituitary tumour delineation, relationship to juxtasellar structures and tumour size, hence facilitating greater success rate in surgical and subsequent clinical management.

Keywords: Magnetic resonance imaging; Pituitary adenoma; SIPAP classification; Tumor volume.

Fig. 1

Coronal contrast enhanced T1 weighted MRI showing 5 grades of suprasellar extension (arrow). A) Grade 0: No bulge in the suprasellar space. B) Grade 1: Upward bulge of adenoma in suprasellar space without reaching the optic chiasm (arrowhead). C) Grade 2: Adenoma reaching optic chiasm but not displacing it. D) Grade 3: Adenoma displacing optic chiasm. E) Grade 5: Adenoma extension causing obstructive hydrocephalus as evident by dilatation of third and lateral ventricles.

Fig. 2

Sagittal contrast enhanced T1 weighted MRI showing 3 grades of infrasellar extension (arrow). A) Grade 0: No inferior bulge with intact floor of sella B) Grade 1: Focal inferior bulge of adenoma as an indirect sign of perforation of dura and floor of sella C) Grade 2: Adenoma extension beneath the sphenoid sinus.

Fig. 3

Sagittal contrast enhanced T1 weighted MRI showing 2 grades of anterior extension (arrow). Dotted line represents perpendicular line to the tubercle of sella A) Grade 0: No extension into anterior cranial fossa B) Grade 1: Extension into anterior cranial fossa.

Fig. 4

Sagittal contrast enhanced T1 weighted MRI showing 3 grades of posterior extension (arrow). Dotted line represents perpendicular line to the dorsum sella. Solid line represents horizontal line to dorsum sella A) Grade 0: No posterior extension B) Grade 1: Posterior-superior growth C) Grade 2: Posterior-inferior growth.

Fig. 5

Coronal contrast enhanced T1 weighted MRI showing 5 grades of parasellar extension (arrow). Dotted lines drawn at the intra and supra cavernous internal carotid arteries A) Grade 0: Extension not beyond the medial tangent. B) Grade 1: Extension up to inter-carotid line. C) Grade 2: Extension up to lateral tangent. D) Grade 3: Extension beyond the lateral tangent E) Grade 4: Total encasement of intra-cavernous carotid artery bilaterally.