Conservative removal of small pituitary tumours: is it justified by the pathological findings?

Endoscopic endonasal surgery for non-invasive pituitary neuroendocrinology tumors with incomplete pseudocapsule

Background

Pituitary neuroendocrinology tumors (PitNETs) with pseudocapsule can be effectively removed by the pseudocapsule-based extracapsular resection technique. In the areas without pseudocapsule, the tumor cells can spread into the adjacent tissues at the cellular level, which brings a great challenge to achieving total tumor resection.

Methods

Our surgical strategy for PitNETs with an incomplete pseudocapsule is to combine the pseudocapsule-based extracapsular resection technique with the intensive excision technique for the removal of the tumor. Specifically, the pseudocapsule-based extracapsular resection technique is applied in the areas with pseudocapsule, while in the areas without pseudocapsule, the intensive excision technique bounded by adjacent normal structures is adopted. Moreover, a pathological examination was performed to determine the situations of pseudocapsule and tumor cell remnant.

Results

All growth hormone-secreting PitNETs achieved biochemical remission after surgery. There was no deterioration of pituitary functions postoperatively, and the preoperative hypopituitarism had improved in all patients postoperatively. In total, two cases suffered a transient diabetes insipidus, and intraoperative cerebrospinal fluid leakage was observed in two cases but no postoperative cerebrospinal fluid leakage in all cases. There was no recurrence during the follow-up. The fragmental pseudocapsule and small tumor remnants were found in the majority of suspicious tissues by histological staining.

Conclusion

The effectiveness and safety of the surgical strategy were preliminarily explored for removing PitNETs without incomplete pseudocapsules. In overview, the pseudocapsule-based extracapsular resection technique is applied in areas with pseudocapsule, while the intensive excision bounded by adjacent normal structures is adopted in other areas.

Pseudocapsule and pseudocapsule-based extracapsular resection in pituitary neuroendocrine tumors

Since Costello et al. proposed the concept of pseudocapsule of pituitary neuroendocrine tumors (PitNETs) in 1936, many studies have been published on its occurrence, development process, histopathology, and morphology. Pseudocapsule has been proposed as the anatomical interface between PitNETs and normal pituitary gland, therefore the so-called pseudocapsule-based extracapsular resection (ER) technique was developed as an extracapsular surgery method for PitNETs,which differs from the conventional intracapsular resection (IR). In recent years, ER has also been widely used in patients of different tumor types, sizes, and age groups, because the pseudocapsule can be identified more clearly under the endoscopy. Endoscopic transsphenoidal resection for PitNETs has become the preferred surgical method. We reviewed relevant literatures in the past 10 years, showing that ER could achieve better rate of gross total resection (GTR) and biochemical remission, and reduce tumor recurrence than IR, without increasing postoperative complications. Therefore, the pseudocapsule and ER should be valued by neurosurgeons and actively promoted clinically.

Peel-off resection of the pituitary gland for functional pituitary adenomas: pathological significance and impact on pituitary function

PURPOSE

Functional pituitary adenomas (FPAs) lacking a well-defined pseudocapsule can invade the adjacent pituitary gland. In such situations, peel-off resection of the adjacent pituitary gland after selective adenomectomy might lead to complete tumor removal, resulting in optimal endocrinological outcomes. Here, we present the significance of peel-off resection of the pituitary gland in patients with FPA in whom complete extracapsular tumor removal cannot be achieved.

METHODS

We performed a retrospective review of 21 patients with FPA who underwent transsphenoidal surgery (TSS). After selective adenomectomy, peel-off resection of the adjacent pituitary gland was performed in 13 patients because complete extracapsular resection could not be achieved, while peel-off resection was not performed in the remaining 8 patients because complete extracapsular resection was accomplished. The clinical outcomes of these groups were compared. The pituitary tissues obtained by peel-off resection were pathologically examined for tumor cells.

RESULTS

Early postoperative biochemical remission was achieved in 20 patients (95.2%). Anterior pituitary functions were not aggravated postoperatively in any patient: however, transient diabetes insipidus (DI) occurred in 2 patients. There were no statistically significant differences in the clinical outcomes of the two groups. A pseudocapsule was pathologically detected in the adjacent anterior pituitary even in patients in whom no pseudocapsule was intraoperatively detected. Tumor cells were pathologically detected in 7 (58.3%) of 12 pituitary tissues examined.

CONCLUSIONS

Peel-off resection of the pituitary gland, which can remove a small tumor cell remnant in the adjacent pituitary, might maximize the effectiveness of TSS with minimal impact on postoperative pituitary function.

Time to Revive the Value of the Pseudocapsule in Endoscopic Endonasal Transsphenoidal Surgery for Growth Hormone Adenomas

OBJECTIVE

To investigate the role of endoscopic endonasal transsphenoidal surgery and the pseudocapsule in the treatment of growth hormone adenomas.

METHODS

The study included 43 patients (age range, 21-64 years) with growth hormone adenomas treated with an endoscopic endonasal approach. We compared the tumor characteristics and surgical outcomes of cases with (group A, 21 cases, from November 2013 to January 2015) and without (group B, 22 cases, from October 2011 to October 2013) extra-pseudocapsule resection.

RESULTS

The preoperative demographics, tumor characteristics, and surgical complications were not significantly different between groups A and B. Postoperative remission without adjuvant therapy was achieved in 18 of 21 cases (85.7%) in group A, which was significantly greater than that observed in group B (12 of 22 cases [54.4%]). In group A, the pseudocapsules were verified by endoscopy and histopathology. The pseudocapsule was removed en bloc with the whole adenoma in only 5 cases (23.8%). For the remaining 16 patients (76.2%), following extra-pseudocapsule dissection, incomplete pseudocapsule removals with intracapsule procedures were achieved.

CONCLUSIONS

The combination of extra-pseudocapsule resection and endoscopy led to a high rate of gross total tumor resection and endocrinologicl remission in acromegalic patients compared with the group with intracapsular resection. Extra-pseudocapsule resection resulted in no additional postoperative complications.

Whole-Sellar Stereotactic Radiosurgery for Functioning Pituitary Adenomas

BACKGROUND:

Functioning pituitary adenomas (FPAs) can be difficult to delineate on postoperative magnetic resonance imaging, making them difficult targets for stereotactic radiosurgery (SRS). In such cases, radiation delivery to the entire sella has been utilized as a radiosurgical equivalent of a total hypophysectomy.

OBJECTIVE:

To evaluate the outcomes of a cohort of patients with FPA who underwent SRS to the whole-sellar region.

METHODS:

This is a retrospective review of patients who underwent whole-sellar SRS for FPA between 1989 and 2012. Sixty-four patients met the inclusion criteria: they were treated with whole-sellar SRS following surgical resection for persistently elevated hormone levels, and (1) no visible lesions on imaging studies and/or (2) tumor infiltration of dura or adjacent venous sinuses observed at the time of a prior resection. The median radiosurgical volume covering sellar structures was 3.2 mL, with a median margin dose of 25 Gy.

RESULTS:

The median endocrine follow-up was 41 months; 22 (68.8%) patients with acromegaly, 20 (71.4%) patients with Cushing disease, and 2 (50.0%) patients with prolactinoma achieved endocrine remission. The 2-, 4-, and 6-year actuarial remission rates were 54%, 78%, and 87%, respectively. New-onset neurological deficit was found in 4 (6.3%) patients following treatment. New-onset hypopituitarism was observed in 27 (43.5%) patients, with panhypopituitarism in 2 (3.2%). Higher margin/maximum dose were significantly associated with a higher remission rate and development of post-SRS hypopituitarism.

CONCLUSION:

Whole-sellar SRS for invasive or imaging-negative FPA following failed resection can offer reasonable rates of endocrine remission. Hypopituitarism following whole-sellar SRS is the most common complication.

Endoscopic distinction between capsule and pseudocapsule of pituitary adenomas

BACKGROUND

Pseudocapsules were first identified in pituitary adenoma surgery in 1936. Since then, the distinction between pituitary capsules and pseudocapsules has been unclear, and the definitions of these entities have varied. In this study, pituitary capsules and extracapsular dissection were examined retrospectively, intra- and extrapseudocapsular resection was evaluated, and dissection of the pituitary adenoma and pseudocapsule was examined prospectively.

METHODS

Between January 2009 and May 2012, endoscopic transsphenoidal pituitary surgery was performed on 224 patients in the Department of Neurosurgery, Kocaeli University Faculty of Medicine, Turkey. Data for 174 patients were analyzed retrospectively between January 2009 and December 2011, and 50 patients treated between December 2011 and May 2012 were included in a prospective study.

RESULTS

In the retrospective phase of the study, capsules were examined in 21 of the 174 patients on whom extracapsular resection had been performed. In the 50 cases treated between December 2011 and May 2012, dissection of the pituitary capsule, adenohypophysis, and pseudocapsule was performed. In 30 patients in the prospective phase of the study, pseudocapsules were identified during intraoperative endoscopic observation. Remission was achieved in 28 of 33 functioning adenomas in the prospective study. The mean follow-up period in this group was 13 months.

CONCLUSION

The endoscopic and histopathological evidence provided in this study demonstrates that the pituitary capsule and pseudocapsule are distinct structures. In addition, it is also shown that extracapsular dissection can be performed in functioning adenomas that invade the suprasellar region. Significantly higher rates of total resection and higher remission rates were observed in cases where extra- and intrapseudocapsular dissection was required.

The pseudocapsule surrounding a pituitary adenoma and its clinical significance

The transsphenoidal approach is currently considered the preferred first-line treatment for pituitary adenoma. With the discovery and application of the pseudocapsule surrounding a pituitary adenoma, transsphenoidal surgery of pituitary adenoma further falls into two categories: "extracapsular" and traditional "intracapsular" resection methods, on the basis of where dissection is performed with respect to the pseudocapsule. Thus, the pseudocapsule can be used as a plane to guide the operation, helps in total resection of pituitary adenoma, and can guide subsequent treatment after surgery.

The 'capsule' of pituitary macroadenomas represents normal pituitary gland: a histopathological study

The goal of trans-sphenoidal pituitary adenoma surgery is radical excision of the tumour with preservation of endocrine function. Our hypothesis was that, even in macroadenomas extending into the suprasellar cistern, the 'capsule' of the tumour is the compressed normal pituitary gland. The biopsy material from 126 patients with pituitary macroadenomas were retrospectively reviewed to look for the presence of normal adenohypophysis. Fourteen patients with macroadenomas operated trans-sphenoidally were studied prospectively, sampling tissue from the periphery of the tumour for histopathology. From the retrospective data, we found that normal adenohypophysis was more often found at histopathology in the extracapsular excisions, rather than in the intracapsular excisions. In the 14 patients studied prospectively, normal adenohypophysial tissue was found histologically at all sites sampled except in areas where the tumour was invasive. In conclusion, while an extracapsular excision would offer the best chance for a surgical cure, preserving parts of the capsule may preserve normal and possibly functioning gland.

Development of a histological pseudocapsule and its use as a surgical capsule in the excision of pituitary tumors

OBJECT

The presence of a histological pseudocapsule around pituitary tumors was noted in the early 1900s. Since that time there has been no emphasis on the sequence of the stages of its development or on the relationship between these stages and the capacity to identify very small pituitary tumors at surgery in patients in whom preoperative imaging has been nondiagnostic. In addition, limited emphasis has been given to the pseudocapsule's use for selective and complete resection of pituitary adenomas.

METHODS

The development of the pseudocapsule was examined by performing histological analysis of portions of pituitary glands removed during 805 operations for Cushing disease. Twenty-five adenomas, each measuring between 0.25 and 4 mm in maximum diameter, were detected in the excised specimens; 17 were adenocorticotropic hormone-positive adenomas and eight were incidental tumors (four prolactin-secreting and four nonsecreting lesions). In 16 tumors the size of the adenoma could be established. The distribution of tumor size in relation to the presence of a histological pseudocapsule indicates a transition from the absence of a reticulin capsule (tumor diameter < or =1 mm) through the initial compression of surrounding tissue (tumor diameter 1-2 mm) to the presence of a multilayered reticulin capsule observed when adenomas become larger (tumor diameter 2-3 mm).

CONCLUSIONS

The absence of a reticulin capsule in cases of very small tumors may contribute to limited localization of these lesions during surgical exploration of the pituitary gland. In this article the authors describe surgical techniques in which the histological pseudocapsule is used as a surgical capsule during pituitary surgery. In their experience, recognition of this surgical capsule and its use at surgery has contributed to the identification of microadenomas buried in the pituitary gland, aided the recognition of subtle invasion of the pituitary capsule and contiguous dura mater, and enhanced the consistency of complete tumor excision with small and large tumors.

Surgical removal of growth hormone-secreting pituitary adenomas with intensive microsurgical pseudocapsule resection results in complete remission of acromegaly

Although some investigators recommended surgical removal of the borders between pituitary adenoma and the surrounding normal pituitary gland, there is so far little documentation of how intensive dissection of the border zone affects the actual clinical remission rate of pituitary adenomas. We investigated the precise histological characteristics of the boundary, using surgical specimens from patients who underwent intensive resection of "microsurgical pseudocapsule" of growth hormone (GH)-secreting pituitary adenomas. Furthermore, we compared the remission rate of acromegaly between subjects with (Group 1) and without (Group 2) intensive resection of microsurgical pseudocapsule in order to correlate the histological complete resection and endocrinological remission. Histologically, most adenomas were in direct contact with normal pituitary gland that formed an increased fibrous component facing the adenoma, without a true histological pseudocapsule. It was impossible to dissect the tumor at exactly the tumor--normal pituitary interface for the whole extent of the pituitary adenoma during surgery, and complete removal of the tumor inevitably included a portion of normal tissue (microsurgical pseudocapsule). The biochemical remission rate was significantly higher in Group 1 than in Group 2 (90.0 vs 61.1%), and Group 1 showed no additional postoperative pituitary hypofunction. The present results suggested that intensive resection of the microsurgical pseudocapsule is essential to accomplish histological and endocrinological total resection of the GH-secreting pituitary adenomas for remission of acromegaly.

Progression of a Nelson's adenoma to pituitary carcinoma; a case report and review of the literature

A 25-year-old woman developed Nelson's syndrome, 3 years after successful bilateral adrenalectomy for Cushing's disease. Despite pituitary surgery and radiotherapy the tumour showed invasive growth, leading to visual disturbance, paresis of the oculomotor nerve and, 34 years after adrenalectomy, to death by widespread purulent leptomeningitis. Autopsy revealed a large adenohypophyseal carcinoma with a metastasis attached to the dura, both tumours showing immunocytochemical staining for ACTH and TSH. We review the literature on metastatic adenohypophyseal carcinoma in Cushing's disease and Nelson's syndrome and discuss the role of proliferation markers as indicators of malignant progression.

Adjuvant therapy for pituitary adenomas: the possible role of photodynamic therapy

Although benign, pituitary adenomas may not always be curable by surgery alone. This is usually owing to dural infiltration and the technical problems of removal of involved dura in the sellar region. In such circumstances, some form of adjuvant therapy may be needed to address residual tumour and forestall recurrence. Radiotherapy and drugs, such as bromocriptine or octreotide, although effective are far from ideal adjuvant therapies and this has led to the study of the effects of photodynamic therapy on pituitary adenomas. It has been shown that photodynamic therapy using the photosensitising drugs haematoporphyrin derivative and aluminium phthalocyanine is active experimentally against these tumours. This could provide another useful weapon to use against these challenging lesions.

The need for adjunctive focused radiation therapy in pituitary adenomas

In pituitary adenomas radiation therapy regardless of the technique should be limited to surgical failures. The delayed onset of beneficial effects and the high rate of pituitary insufficiency have to be weighed against the good surgical and/or medical results in the treatment of these tumours. Unfortunately surgical outcome is almost invariably correlated with invasive growth. Invasiveness is statistically significantly correlated with tumour size, as well as with high proliferation rates, which can be measured by immunohistological methods such as mAB KI-67. Owing to the good results of medical treatment, radiation therapy is usually unnecessary in prolactinomas. Patients with persistent hypersecretion of growth hormone after unsuccessful surgery may represent the ideal candidates for radiation therapy, whereas patients with persistent Cushing's disease need cure for hypercortisolism without delay. In patients with residual tumour due to non functioning adenomas, radiation therapy should only be given if the proliferation rate is high.

Interactions between normal and tumoral tissues at the boundary of human anterior pituitary adenomas. An immunohistochemical study

We studied the boundary between adenoma and peritumoral anterior pituitary tissues in order to understand their mutual interactions during tumour progression. We selected 18 adenomas of different secretory type, grade and invasiveness in which fragments of peritumoral anterior pituitary were still attached to the adenoma. Immunohistochemistry was performed on serial sections with markers of the basement membranes (type IV collagen), the hormone-producing cells of the normal and neoplastic anterior pituitary, and the folliculo-stellate cells (S-100 protein). In passing from tumour to gland, localized areas of passive compression of the normal gland were seen in only 3 cases. In all the tumours, the boundary consisted partly or solely of a transitional zone characterized by the presence of enlarged cell-cords. Openings in the basement membrane of these enlarged cell-cords were seen in contact with the tumour tissue. Normal and neoplastic cells intermingled in the transitional zone. Normal residual cells could be seen in the central area of the tumour but no adenomatous cells were observed in the gland around the tumour. Folliculo-stellate cells were concentrated in the vicinity of the transition zone. These findings favour the existence of an active process of adenoma expansion within the normal parenchyma, without noticeable infiltration of tumour cells into surrounding gland.

In vitro study of the effect of photodynamic therapy on pituitary adenomas

Photodynamic therapy (PDT) has been employed in the management of recurrent cerebral gliomas, but its activity against pituitary adenomas has not been specifically studied. An in vitro study of the effects of PDT against a variety of pituitary adenomas was conducted. It was found that PDT using haematoporphyrin derivative as a photosensitizer showed dose dependent activity against a variety of pituitary adenomas. The activity of PDT against pituitary adenomas should be investigated further and may hopefully provide a useful form of adjuvant therapy for preventing recurrence of micro-invasive pituitary adenomas or dealing with established recurrence after surgery and radiotherapy.

MRI of pituitary macroadenomas with reference to hormonal activity

In 115 patients with pituitary macroadenomas, the findings on mid-field MRI were correlated with the hormonal activity of the tumours. Adenomas secreting growth hormone (GH), prolactin (PRL) and clinically nonsecretory adenomas were studied. Tumour size, invasiveness and signal intensity patterns were recorded. Relaxation times and ratios of signal intensity and proton density (relative to the corpus callosum) were analysed in areas of apparently solid tissue in a subgroup of 59 previously untreated patients. Invasiveness was more common in PRL- and GH-secreting adenomas than in the nonsecreting ones. Diffuse invasion of the base of the skull was most common in prolactinomas, and associated with a lower frequency of suprasellar tumour extension. In prolactinomas, a correlation was found between the maximum serum PRL level and tumour size. Haemorrhagic, cystic or necrotic areas were less common in GH-secreting tumours than in the other types. Haemorrhage was more common in prolactinomas than in nonsecreting tumours. MR parameters were similar in prolactinomas and nonsecreting adenomas, but indicated a smaller amount of water in GH-secreting tumours.

Pituitary adenomas with parasellar invasion

Pituitary adenomas with extension into the parasellar space, the so called "cavernous sinus" can be demonstrated best using MRI. To improve the delineation from the venous compartments the use of unenhanced and enhanced MRI scans is essential. In 25 pituitary adenomas with surgically proven infiltration into the space of the cavernous sinus we correlated the MRI findings with our surgical observations. When the adenoma encases the intracavernous internal carotid artery or reaches as far as to the lateral aspect of the artery, invasion was present in all cases. The critical area where invasion could not be predicted from MRI is the distance between the medial and the lateral aspect of the intracavernous internal carotid artery. By measurement with the monoclonal antibody KI-67 it could be shown, that pituitary adenomas infiltrating the parasellar space have a statistically significant higher growth rate (p less than 0.001), compared to non-invasive adenomas. This is of special interest, because surgical cure becomes unlikely, when invasion into the space of the cavernous sinus is present.

Enlarged adenomectomy for enclosed prolactinomas: a preliminary study of 26 cases

Preliminary results obtained from 26 cases of prolactinomas less than 20 mm in diameter after treatment by enlarged adenomectomy are described. The operation consisted in removal of the adenoma, a layer of normal pituitary at the outer edge of the tumour and the pituitary capsule in contact with the sellar meninges. 24 women and 2 men were involved whose prolactin levels (PRL) were less than 200 ng/ml. All presented abnormal PRL responses to Thyrotropin releasing hormone (TRH) and Metoclopramide (MCP) tests and an absence of a nocturnal rise in the sleep cycle study. Postoperatively, three patients developed transitory diabetes insipidus and five transitory adrenal insufficiency. Gonadotropin reserve was always found normal. All 24 women resumed normal menstrual cycles and two became pregnant within one year. From a serological viewpoint, after surgery 100% of patients were found to be normal for levels of prolactin but only 85% turned to normal dynamic tests. The results of this small series of enlarged adenomectomies seem better than those obtained using selective adenomectomy, but must be confirmed with time.

The pathology of non-functional pituitary adenomas

Pituitary adenomas encompass the endocrine, symptomatic or functionally active and the non-functional, null cell or functionally inactive. According to their sizes, they can be very small, also called microadenomas, or they can be very large, "invasive", or macroadenomas usually without clinical evidence of hypersecretion. The "invasive" pituitary adenomas usually grow beyond the confines of the sella turcica. These adenomas are characterized anatomically by displacement, distortion and compression of the adjacent sellar structures. They may destroy bone and penetrate into the nasal cavity or into the cavernous sinuses. They may distend the diaphragm sella and compress the hypothalamus and the optic chiasm and optic tracts or they may distort the cerebral cortex or penetrate into the third ventricle. "Invasive" pituitary adenomas are characterized clinically by visual disturbances, headaches, seizures, diabetes insipidus and by hypothalamic dysfunction mimicking some endocrinologically active pituitary adenomas. The diagnosis of invasive pituitary adenomas can be suspected clinically and can be confirmed by radiological evidence of destruction of the sella turcica and its boundaries or by neurosurgical intervention and finally by necropsy findings of "invasion" of the parasellar and suprasellar structures.

Results of transsphenoidal microsurgery for growth hormone-secreting pituitary adenoma in a series of 214 patients

Of 214 patients with acromegaly who underwent transsphenoidal microsurgical resection of a pituitary adenoma, 54% had growth hormone (GH) levels below 5 ng/ml and 74% had levels less than 10 ng/ml immediately after surgery. Among the 174 patients who could be contacted for long-term follow-up review (average duration 76 months), most recent GH determinations were available for 165. Of these 165 patients, 131 (79.4%) have a GH level less than 5 ng/ml and 153 (92.7%) have a level below 10 ng/ml; these represent 75.3% and 87.9%, respectively, of the total 174 patients reviewed. Fifty-two patients received postoperative radiation therapy. Nine patients underwent reoperation. There were five cases of tumor recurrence following an apparent surgical cure (4.3%), nine new instances of anterior pituitary hypofunction (5%), and five failures of multimodality therapy (2.3%). There were no perioperative deaths, five cases of cerebrospinal fluid leak requiring surgical repair (2.2%), and four cases of postoperative meningitis (1.8%). Permanent diabetes insipidus did not occur. Two of 52 patients who were irradiated postoperatively had severe complications; 23 (54.8%) of 42 patients who were available for follow-up evaluation had developed panhypopituitarism; and eight (19%) of 42 had normal pituitary function an average of 44 months postirradiation.

Treatment and recurrences in 135 pituitary adenomas

In 135 operated pituitary adenomas of different histological nature, seen over 20 years, the initial treatment was surgical, by trans-sphenoidal or transcranial approach depending on the tumour extent, followed by radiotherapy if necessary. In spite of modern investigation methods, diagnosis is still often made late, so that 118 of our cases already had visual symptoms. After surgery alone (87 cases) made by the same team recurrences occurred in 16%. Reoperations (14 cases) were generally more difficult and could also be followed by new recurrences needing finally radiotherapy with still positive results. Two cases had initial radiotherapy, the other 46 cases were treated by surgery and radiotherapy with a recurrence level of 8.3%. These results indicate the need to use immediate postoperative radiotherapy in every pituitary adenoma showing even the slightest invasive potential because radical surgery is hypothetical and recurrences possible. The recurrence of pituitary adenomas remains a difficult problem of anticipation and of curative management. Our position in terms of these benign tumours is to adopt readily this therapeutic course: surgery followed by radiotherapy, which provides the best prognosis without major risks.

Pathology of invasive pituitary tumors with special reference to functional classification

Pituitary adenomas may remain intrasellar or infiltrate dura and bone. Invasive adenomas are not considered to be malignant; in biological behavior they are between non-infiltrative adenomas and pituitary carcinomas. The latter are defined as tumors with subarachnoid, brain, or systemic metastasis. Invasion may be defined radiologically, operatively, or histologically. On the basis of operatively assessed tumor size and gross invasion of dura and bone as well as immunocytochemical and ultrastructural analysis of 365 pituitary adenomas, the following data were obtained. There were 23 growth hormone (GH)-cell adenomas: 14% microadenomas and 86% macroadenomas; their overall frequency of invasion was 50%. There were 24 prolactin (PRL)-cell adenomas: 33% microadenomas and 67% macroadenomas, with an overall frequency of invasion of 52%. Mixed GH-cell and PRL-cell adenomas were found in 35 cases; 26% were microadenomas and 74% were macroadenomas, and the overall frequency of invasion was 31%. Sixty patients had adrenocorticotropic hormone (ACTH)-cell adenomas (Cushing's disease): 87% microadenomas and 13% macroadenomas; the overall frequency of invasion was 25% (in 8% of microadenomas and 62% of macroadenomas). Twenty patients had ACTH-cell adenomas (Nelson's syndrome): 30% microadenomas and 70% macroadenomas; the overall frequency of invasion in these cases was 50% (in 17% of microadenomas and 64% of macroadenomas). Silent ACTH-cell adenomas, 100% macroadenomas, were found in 11 patients, with an 82% frequency of invasion. There were 32 follicle-stimulating and luteinizing hormone adenomas, all macroadenomas, with a frequency of invasion of 21%. Four patients had thyroid-stimulating hormone adenomas, all macroadenomas, with a 75% frequency of invasion. Null-cell adenomas were found in 93 cases: 2% microadenomas and 98% macroadenomas, with a frequency of invasion of 42%. There were 63 plurihormonal adenomas (GH, PRL, glycoprotein): 25% microadenomas and 75% macroadenomas, with a 50% overall frequency of invasion. Based on this study, and on their usual frequency of occurrence, the estimated rate of gross invasion by pituitary adenomas of all types is approximately 35%. It is concluded that immunocytochemical and ultrastructural characteristics of pituitary adenomas reflect the tendency of these tumors to infiltrate and hence may be of prognostic significance.

The occurrence of dural invasion in pituitary adenomas

This report describes 60 dural specimens from patients with pituitary adenomas treated by transsphenoidal microsurgery, and attempts to define more precisely the clinical and pathological correlation of microscopic dural invasion. Analysis of the adenomas was based on four characteristics; size, surgical invasiveness (based on the surgeon's assessment of involvement by tumor of bone, dura, or cavernous sinus), histological evidence of invasion, and immunohistochemical staining characteristics. The incidence of surgical invasiveness (24 cases, 40%) was greater than previously reported, but most important was the frequent occurrence of microscopic dural invasion (51 cases, 85%). There was a clear progression of microscopic evidence of dural invasion with increasing tumor size: 69%, 88%, and 94% of the dural specimens from microadenomas, macroadenomas, and tumors with suprasellar extension, respectively, showed microscopic dural invasion. A correlation of invasiveness with immunohistochemical classification of tumor type was not evident.

Long-term growth hormone responses to nonspecific hypothalamic hormones in acromegalic patients

Nonspecific hypothalamic hormones such as thyrotropin-releasing hormone or luteinizing hormone-releasing hormone, or both, elicited abnormal growth hormone responses in 73 of 108 (67.6%) acromegalic patients. After transsphenoidal adenomectomy, the provocative tests using these hormones were repeated in 26 patients with abnormal preoperative growth hormone responses to study variations in these responses during a 1-8-year observation period (average duration, 4 years). After surgery, 7 of the 26 patients regained normal basal growth hormone levels (less than 5 ng/mL) and manifested normal responses to the hypothalamic hormones. During the postoperative observation period, their basal growth hormone levels remained normal as did their responses to provocation with hypothalamic hormones, confirming that the adenoma had been completely resected. Eight other patients demonstrated normal growth hormone levels after surgery; however, they continued to have abnormal responses to provocation with hypothalamic hormones, suggesting the presence of residual adenomatous tissue in the gland. These patients manifested no marked increase in basal or peak growth hormone levels during the follow-up period (from less than 1 to less than 7.5 years) and they were all in clinical remission without any other treatment. Only one incompletely adenomectomized patient who had received no additional treatment experienced regrowth of the tumor. The main factor affecting the surgical results appears to be the preoperative basal growth hormone level, because abnormal growth hormone secretion ceased in all patients who had manifested preoperative levels below 45 ng/mL. Technical refinements of the operative procedure are another important factor in the postoperative outcome. Peritumoral tissue resection after simple selective adenomectomy is mandatory for better surgical results. Our studies indicate that fairly good results can be obtained without risk of the recurrence of the tumor or regrowth, when postoperative growth hormone levels are below 5 ng/mL and that the results are not affected by the postoperative growth hormone responses to provocation with hypothalamic hormones.

Long term results of radical hypophysectomy for Cushing's disease

Sixteen consecutive cases of Cushing's disease were treated by radical transphenoidal hypophysectomy. Surgical removal was not possible in two cases. Of the other 14, there was total clinical and biochemical remission of the disease in 13 and partial remission in one. Some form of replacement therapy has been necessary in 11 out of the 14 cases. During a long period of postoperative clinical and biochemical assessment extending over 5-14 years (average 8 years) there have been no recurrences.

Hyperthyroidism due to a thyrotrophin-secreting microadenoma

We report a 63-year-old female with a TSH-secreting pituitary adenoma causing hyperthyroidism. This case is apparently unique, and challenges the present concept of dividing patients with inappropriate TSH secretion into tumour and non-tumour groups on the basis of conventional pituitary fossa radiology.

Successful treatment of Cushing's disease using yttrium-90 rods

Interstitial irradiation using yttrium-90 (90Y) rods implanted by needle into the pituitary gland was used as primary treatment in 16 patients with pituitary dependent Cushing's disease. Clinical and biochemical remission was observed within three or six months in 13 and in the remaining three after a supplementary implant. There was no perioperative morbidity. Follow-up from the time of definitive operation ranged from six to 123 months (mean 39). No recurrence has been observed. The return of a normal diurnal cortisol rhythm has been observed in 10/12 patients studied after remission. Some form of long-term pituitary hormone replacement therapy was required in only the six patients who had received the largest irradiation dose. Implantation of 90Y is safe and effective treatment for patients with Cushing's disease, comparing favourably with selective trans-sphenoidal pituitary surgery.