Technical Considerations of Transsphenoidal Removal of Fibrous Pituitary Adenomas and Evaluation of Collagen Content and Subtype in the Adenomas.

Abstract

Pituitary adenomas are usually soft, but 5-13.5% are fibrous adenomas which are difficult to remove. Magnetic resonance (MR) imaging and operative findings were evaluated in eight patients (12.1%) with fibrous pituitary adenoma among 66 patients. Tumor specimens were examined histologically and immunohistochemically for collagen content and subtypes. Seven patients had clinically inactive nonfunctioning pituitary adenomas and one patient growth hormone-secreting adenoma. All patients underwent transsphenoidal surgery. Four cases were giant adenomas with suprasellar extension of more than 2 cm. T 1 -and T 2 -weighted MR imaging showed the tumors as nearly isointense to the surrounding brain, except in one case where the tumor was high intense on T 2 -weighted MR imaging. All tumors required piecemeal resection using a micro-dissector and tumor forceps. Four tumors of maximum size more than 3 cm needed a second operation. The interface between the thinned normal pituitary gland and fibrous adenoma was intended to identify at the anterior-superior portion in recent four cases, which was helpful to remove the tumors and preserve pituitary functions. Histological examination revealed prominent deposition of collagen in the perivascular area. The percentage of collagen content in fibrous adenomas was more than 5% and significantly higher than that in soft adenomas and normal pituitary glands. Immunohistochemical examination showed positive staining for collagen types I and III in the fibrous adenomas, but only for type V collagen in the normal pituitary glands. Large fibrous adenomas can be resected by transsphenoidal surgery which may require two-stage operations. Identification of the interface between the normal pituitary gland and adenoma is helpful to remove fibrous adenomas and to preserve pituitary functions. We propose that firm adenomas containing more than 5% collagen are``fibrous'' adenomas.

Is There Any Congruity Between Tumor Consistency in Pituitary Macroadenomas and Preoperative Diffusion Weighted Imaging and Apparent Diffusion Coefficient (ADC) Map?

“…The appli- In this study, we assessed the predictive value of both conventional MRI and DWI techniques for tumor consistency in 45 macroadenomas while considering both surgical and pathological findings. As previously reported, we found that the density of the collagen content of tumor specimens was correlated with tumor consistency (3,11). The collagen content of the hard tumors was significantly higher than that of the tumors with soft and intermediate consistency.…”

“…The extent of excision through this route depends on the size, invasiveness, and consistency of the tumor. In this regard, the main limitation of the microscopic transsphenoidal technique may be the hard consistency of the tumor (2,3). Most adenomas are soft and easily curetted by suctioning.…”

“…Most adenomas are soft and easily curetted by suctioning. However, about 10% of macroadenomas are fibrous and poorly amenable to suction and curettage (3). In such cases, an adequate tumor resection may not be achievable via a transsphenoidal approach and a more extensive transsphenoidal approach or a second operation like transcranial surgery or radiation is often required (4)(5)(6).…”

“…Previous studies have evaluated conventional MRI features in the prediction of macroadenomas consistency and histologic features but the results had been inconsistent. Some authors have reported that macroadenomas with low T2-weighted signal intensity, as a measure of low water content (2,3,7), and more homogenous enhancement mostly happen to be dense, fibrous, and contain more collagen (8). On the contrary, others have found no correlation between tumor consistency and MRI findings (3,(9)(10)(11).…”

Craniocaudal Extension as an Indication of Surgical Outcome in Transsphenoidal Surgery for Pituitary Adenomas

“…Transsphenoidal surgery can be done as an initial treatment followed by a transcranial approach [13,17]. A second staged transsphenoidal approach can be contemplated if there is descent of the remaining tumor in the sella [18,19]. Modified and extended endoscopic transsphenoidal approach can be also used [20][21][22].…”