Scheithauer, Bernd W.

Pituitary enlargement, development of pregnancy cells and prolactin cell hyperplasia are known to occur in pregnancy. In the present work, we assessed microvessel densities in the 20 pituitaries of pregnant women who passed away. Twenty pituitaries of age matched non‐pregnant women who died from non‐endocrine diseases were used as controls. The autopsy obtained pituitaries were formalin fixed and paraffin embedded. Slides were immunostained for adenohypophysial hormones and for CD‐34, an endothelial cell biomarker using the streptavidin‐biotin‐ peroxidase complex method. Microvessel densities were evaluated quantitatively in 10 random high‐ power fields. For statistical analysis, the chi‐square and Fisher exact tests were applied. The results confirmed that the pituitaries of pregnant women increased in weight and contained more PRL immunopositive cells compared to the controls. The formation of pregnancy cells was also evident. In the pituitaries of pregnant women compared to the control, microvessel densities were significantly higher. The cause of increased vascularity remains to be evaluated. This work was supported by the Jarislowsky and Lloyd Carr‐Harris Foundations.

Angiogenesis is a crucial event in tumor growth, invasion and development of metastasis. Endoglin (CD‐105), a disulfide‐linked homodimeric cell membrane glycoprotein of 180 kDa, located on chromosome 9q and binds to several components of the TGF beta family. In contrast to other endothelial cell markers, endoglin can be demonstrated only in proliferating endothelial cells. We investigated endoglin immunoexpression in various surgically removed human pituitary tumor types and compared the results with CD‐34 immunoexpression. For immunohistochemistry, the streptavidin‐biotin‐peroxidase complex method was used and the number of vessels were counted in 10 low power fields. Results show that endoglin immunostains fewer vessels than CD‐34 in every pituitary adenoma type. The number of endoglin immunopositive vessels is highest in untreated prolactinomas and subtype 3 silent pituitary adenomas and lowest in subtype 1 silent corticotroph adenomas and GH adenomas exposed to somatostatin analogs and prolactinomas exposed to dopamine agonists. Our findings are consistent with the view that endoglin is upregulated in proliferating endothelial cells and its expression can be used as an indicator of vascular neoformation in pituitary tumors. The low levels of endoglin expression in pituitary tumors exposed to somatostatin or dopamine agonists suggests that these therapeutic drugs can inhibit angiogenesis.

Objective MGMT expression in brain and pituitary tumors has been correlated with temozolomide treatment. Few medical therapies are available in patients with Nelson Syndrome. The aim of the present study was to assess immunohistochemical expression of MGMT in ACTH‐secreting pituitary adenomas in patients with Nelson Syndrome. Methods Our material consisted of specimens from ACTH‐secreting pituitary adenomas from patients with Nelson Syndrome. Immunohistochemical staining for MGMT was performed using the streptavidin‐biotin‐peroxidase complex method. MGMT immunoreactivity was assessed microscopically and recorded as an estimated percentage of nuclear MGMT immunopositivity. (0=none, 1=<10%, 3=<50%, 4=>50%) Results Male:Female ratio was 3:5, with average patient age being 62 (range 57–66). Five of the eight specimens (65%) exhibited no MGMT immunoreactivity, with two out of eight cases (25%) showing slight MGMT immunopositivity and one out of eight cases (12%) demonstrating moderate MGMT immunopositivity (<25%). Conclusions Temozolomide therapy may be useful in patients with Nelson Syndrome. Absent or low MGMT staining in brain and other neoplasms has been shown to correlate with successful treatment with temozolomide, and recent reports assessing aggressive pituitary adenomas suggest similar outcome.

Abstract Context. —Pseudoneoplasms of the nervous system vary greatly in nature. Ranging from inflammatory to autoimmune, infectious, malformative, reactive, degenerative, and radiation induced, they all mimic true tumors. Thus, they have the potential to mislead clinicians, radiologists, and pathologists alike. Their clinical and/or neuroimaging and histologic features are readily misinterpreted as tumor. Knowledge of the pitfalls is essential to avoid mismanagement, specifically overtreatment. In such instances, pathologists must take the entire clinical picture into consideration, acquainting themselves with presenting symptoms, physical findings, and neuroimaging. Objective. —To present 10 examples of pseudoneoplasms of the nervous system, analyze the basis for their mimicry, and discuss their differential diagnosis. Data Sources. —Review of the pertinent literature related to pseudoneoplasms of the nervous system and review of the consultation files of one of the authors (B.W.S.). Conclusions. —The identification of tumor mimics may be difficult under the best of circumstances, and maintaining a broad differential diagnosis as well as application of a variety of immunocytochemical and occasionally ultrastructural and/or molecular genetic methods is essential to arrive at a correct diagnosis.

A 38‐year‐old woman, status‐post renal transplant on immunosuppressive therapy, presented with fever, hypotension, and painful erythematous nodules on her chest, abdomen, and back. Skin biopsy revealed panniculitis with fat necrosis, and corresponding cultures showed no growth. Over the next 5 days, she became obtunded and developed a left hemiparesis. MRI showed non‐enhancing bilateral lesions in the cerebral cortex. She deteriorated and died. At autopsy, the 954 gram brain demonstrated flattened gyri and multiple disseminated necrotic foci. Microscopically, numerous cysts and trophozoites were identified within necrotic foci, consistent with Acanthamoeba spp. Review of the skin biopsy revealed similar organisms. Unlike primary amebic meningoencephalitis in healthy children and young adults caused by Naglearia fowlerii, encephalitis due to Acanthamoeba spp. is a subacute, progressive disease of immunocompromised patients. The double‐walled, cysts of Acanthamoeba spp. stain with H&E and Gomori Methenamine Silver, and may be mistaken for a fungus. Knowledge of the epidemiology and microscopic appearance of Acanthamoeba spp. is essential for accurate and timely diagnosis of this serious and potentially treatable infection.

Following traumatic brain injury (TBI) approximately 25% of patients develop partial or complete hypopituitarism (HP). In our previous histologic study we found no changes in the pituitaries of patients who died instantly after TBI (Group I). In 43% of patients who survived 1‐7 days acute pituitary infarcts were apparent (Group II). In the present work, 3 group I and 7 group II pituitaries with infarcts were selected for histological and immunohistochemistry (IH) evaluation. IH was performed for adenohypophyseal hormones by the streptavidin‐biotin‐peroxidase method. In group I pituitaries, no histological changes were found and IH showed normal distribution and intensity for GH, PRL, ACTH, TSH, FSH, LH and α‐subunit (α‐SU). In group II pituitaries acute infarct (size range: 10% to 80%) was evident. IH in the non‐necrotic areas revealed no significant change. In the area of early necrosis the dying cells were still immunopositive (IP) for GH, PRL, ACTH, TSH, FSH, LS, and α‐SU. Even in the necrotic cells with loss of cell membrane, nuclear pyknosis, rhexis and lysis IP cytoplasms were still apparent indicating that hormone release is affected by ischemia. Subsequently the intensity of IP cells gradually decreased and IP granules leaked out from the necrotic cells and were seen extracellularly. In conclusion infarction and loss of adenohypophyseal cells may contribute to HP but other factors should also be considered.

Gliosarcomas are uncommon primary tumors of the central nervous system defined as exhibiting both glial and sarcomatous components. Examples in which the glial component is ependymal are exceedingly rare. To our knowledge, the literature contains only three single case reports. We identified eight examples in our files. The patients included 4 females and 4 males (mean age, 31 years; range, 2–63). Tumor locations included temporal lobe (n=2), parietooccipital lobe (n=2), occipital lobe (n=1), insula (n=1), cerebellopontine angle (n=1), and right lateral ventricle (n=1). A sarcomatous component was present at presentation in five cases. In all but one case, a grade II ependymoma, the glial element at presentation was anaplastic (WHO grade III). The sarcomatous component consisted of a reticulin rich, GFAP negative, pleomorphic spindle cell sarcoma/fibrosarcoma in 7 instances and an osteosarcoma in one. Fluorescence in situ hybridization (FISH) comparing the glial and sarcomatous elements for chromosomal aberrations is in progress. Follow‐up is currently available in 4 patients. Three patients expired 4 to 19 months after initial resection, and one is alive without recurrence 12 years after a gross total resection. Although rare, ependymomas must be included among the gliomas prone to undergo sarcomatous metaplasia. Such tumors are associated with particularly aggressive behavior.

SNAP‐25, a synaptosome associated exocytosis protein of 25 kDa plays an important role in the secretory activity of several endocrine cells. In the present study, we investigated 15 PRL, 10 GH, 5 ACTH, 5 TSH, 15 FSH/LH/ alpha subunit producing, and 5 null cell adenomas. Surgically removed, formalin‐fixed and paraffin embedded human pituitary tumors were used. Sections were immunostained by the streptavidin‐biotin‐peroxidase complex method. The results showed that 10 PRL producing adenomas were strongly immunoreactive for SNAP‐25. The immunopositive material was located mainly on the plasmalemma. The nuclei were immunonegative, the cytoplasm was mildly immunopositive in several cells. Treatment of patients with dopamine agonists before surgery decreased markedly SNAP‐25 immunopositivity in 5/10 cases. In GH producing adenomas SNAP‐25 was seen in 5 cases. Immunopositivity was mild‐ moderate, membrane bound and cytoplasmic. Somatostatin analogs caused no marked reduction in immunopositivity (5 cases). Other adenoma types were practically immunonegative. Among human pituitary adenomas only PRL producing tumors release their secretory granules via exocytosis as was demonstrated by electron microscopy. This observation is concordant with our results. In dopamine agonist treated patients, decreased SNAP‐25 expression in PRL producing adenoma cells is consistent with reduction of blood PRL levels.

Spontaneous intracerebral hemorrhage is an uncommon but recognized first presentation of both primary and metastatic brain tumors. The rate of tumor‐related intracranial hemorrhage is variably reported from less than 1% to 14.6%. Hemorrhage in primary gliomas occurs in 3.7 to 7.2% of cases, mainly in glioblastoma and oligodendroglioma with low‐grade astrocytomas accounting for less than 1%. Hemorrhage associated with pilocytic astrocytomas is only sporadically reported. A series of pilocytic astrocytomas presenting as a hemorrhages prompted us to examine the incidence of bleeding in these tumors. Cases with a confirmed tissue diagnosis of pilocytic astrocytoma from 1994–2005 were reviewed retrospectively. Only subjects with radiographic evidence of hemorrhage on CT and/or MRI occurring prior to biopsy or resection and in the absence of trauma or specific vascular pathologies were included. Of 138 patients with histological pilocytic astrocytoma, the average age at diagnosis was 23 years. Eleven (8%) patients (5M, 6F) had evidence of hemorrhage at presentation. Its occurrence was independent of tumor location. Hemorrhage in pilocytic astrocytoma is likely related to the frequently observed abnormal vasculature seen in these tumors, occurs with a greater frequency than previously thought, and should be considered in the differential diagnosis of spontaneous intracerebral hemorrhage.

Malignant nerve sheath tumors involving cranial nerves are rare. We identified 13 cases of MCNST arising in cranial nerve or from benign nerve sheath tumors, all but three being intracranial. The patients included 10 males and 3 females, one pediatric (5 years) and the remainder ranging in age from 23 to 69 years (mean, 40). The vestibular (n=5) and vagal nerves (n=3) were favored sites, followed by posterior fossa (n=2), facial nerve (n=1), frontal lobe parenchyma (n=1) and the lateral ventricle (n=1). Some patients were known to have NF1(n=3) or probable NF2 (n=1). Three tumors arose in transition from a conventional schwannoma and one from a plexiform neurofibroma. The majority of the tumors (n=11) were high grade (5 WHO III and 6 WHO IV) lesions. Immunohistochemistry was performed in 11 cases; S‐100 protein reactivity was diffuse (n=1), partial (n=2), focal (n=5) or negative (n=3). Collagen IV was also diffuse (n=2), partial (n=3), focal (n=5) or negative (n=1). p53 protein staining was high (n=7), moderate (n=2), or low (n=2). Clinical follow‐up was available in 10 cases; of the 8 patients who died, six patients did so within six months of surgery, and two within three years. Only one tumor, a grade IV MCNST with heterologous bone formation, developed extensive spinal leptomeningeal drop metastases. The one pediatric patient is alive at 8 years. No clinically apparent systemic metastases were encountered.