Diagnosis and Management of Pituitary Adenomas: A Review.

Importance: Pituitary adenomas are neoplasms of the pituitary adenohypophyseal cell lineage and include functioning tumors, characterized by the secretion of pituitary hormones, and nonfunctioning tumors. Clinically evident pituitary adenomas occur in approximately 1 in 1100 persons. Observations: Pituitary adenomas are classified as either macroadenomas (≥10 mm) (48% of tumors) or microadenomas (<10 mm). Macroadenomas may cause mass effect, such as visual field defects, headache, and/or hypopituitarism, which occur in about 18% to 78%, 17% to 75%, and 34% to 89% of patients, respectively. Thirty percent of pituitary adenomas are nonfunctioning adenomas, which do not produce hormones. Functioning tumors are those that produce an excess of normally produced hormones and include prolactinomas, somatotropinomas, corticotropinomas, and thyrotropinomas, which produce prolactin, growth hormone, corticotropin, and thyrotropin, respectively. Approximately 53% of pituitary adenomas are prolactinomas, which can cause hypogonadism, infertility, and/or galactorrhea. Twelve percent are somatotropinomas, which cause acromegaly in adults and gigantism in children, and 4% are corticotropinomas, which secrete corticotropin autonomously, resulting in hypercortisolemia and Cushing disease. All patients with pituitary tumors require endocrine evaluation for hormone hypersecretion. Patients with macroadenomas additionally require evaluation for hypopituitarism, and patients with tumors compressing the optic chiasm should be referred to an ophthalmologist for formal visual field testing. For those requiring treatment, first-line therapy is usually transsphenoidal pituitary surgery, except for prolactinomas, for which medical therapy, either bromocriptine or cabergoline, is usually first line. Conclusions and Relevance: Clinically manifest pituitary adenomas affect approximately 1 in 1100 people and can be complicated by syndromes of hormone excess as well as visual field defects and hypopituitarism from mass effect in larger tumors. First-line therapy for prolactinomas consists of bromocriptine or cabergoline, and transsphenoidal pituitary surgery is first-line therapy for other pituitary adenomas requiring treatment.

Immune-checkpoint inhibitors in pituitary malignancies.

To date, there are no standardized systemic treatment options for patients with metastatic pituitary carcinoma progressed to chemo and radiation therapy. Immune-checkpoint inhibitors (ICIs) have been successfully assessed in other solid malignancies and could be a concrete hope for these patients. We performed a critical review of the literature aimed to evaluate studies assessing ICIs in pituitary malignancies. We also conducted research about published translational data assessing immune-contexture in these malignancies. Some preliminary reports reported a successful administration of pembrolizumab or the combination between nivolumab and ipilimumab in patients with metastatic ACTH-secreting pituitary carcinomas. Translational data suggest that adenomas secreting growth hormone and ACTH have a suppressed immune-microenvironment, which could be more likely to benefit from ICIs. Immune-checkpoint inhibitors can be an effective treatment in patients with pituitary carcinoma and maybe also recurrent adenoma. Tumors secreting growth hormone and ACTH are more likely to benefit from ICIs due to a different immune-microenvironment.

Acute social defeat stress upregulates gonadotrophin inhibitory hormone and its receptor but not corticotropin-releasing hormone and ACTH in the Male Nile Tilapia (Oreochromis niloticus).

Stress impairs the hypothalamic-pituitary-gonadal (HPG) axis, probably through its influence on the hypothalamic-pituitary-adrenal (= interrenals in the teleost, HPI) axis leading to reproductive failures. In this study, we investigated the response of hypothalamic neuropeptides, gonadotropin-inhibitory hormone (GnIH), a component of the HPG axis, and corticotropin-releasing hormone (CRH) a component of the HPI axis, to acute social defeat stress in the socially hierarchical male Nile tilapia (Oreochromis niloticus). Localization of GnIH cell bodies, GnIH neuronal processes, and numbers of GnIH cells in the brain during acute social defeat stress was studied using immunohistochemistry. Furthermore, mRNA levels of GnIH and CRH in the brain together with GnIH receptor, gpr147, and adrenocorticotropic hormone (ACTH) in the pituitary were quantified in control and socially defeated fish. Our results show, the number of GnIH-immunoreactive cell bodies and GnIH mRNA levels in the brain and the levels of gpr147 mRNA in the pituitary significantly increased in socially defeated fish. However, CRH and ACTH mRNA levels did not change during social defeat stress. Further, we found glucocorticoid type 2b receptor mRNA in laser captured immunostained GnIH cells. These results show that acute social defeat stress activates GnIH biosynthesis through glucocorticoid receptors type 2b signalling but does not change the CRH and ACTH mRNA expression in the tilapia, which could lead to temporary reproductive dysfunction.

Targeting the TR4 nuclear receptor with antagonist bexarotene can suppress the proopiomelanocortin signalling in AtT-20 cells.

Drug options for the life-threatening Cushing's disease are limited, and surgical resection or radiation therapy is not invariably effective. Testicular receptor 4 (TR4) has been identified as a novel drug target to treat Cushing's disease. We built the structure model of TR4 and searched the TR4 antagonist candidate via in silico virtual screening. Bexarotene was identified as an antagonist of TR4 that can directly interact with TR4 ligand binding domain (TR4-LBD) and induces a conformational change in the secondary structure of TR4-LBD. Bexarotene suppressed AtT-20 cell growth, proopiomelanocortin (POMC) expression and adrenocorticotropin (ACTH) secretion. Mechanism dissection revealed that bexarotene could suppress TR4-increased POMC expression via promoting the TR4 translocation from the nucleus to the cytoplasm. This TR4 translocation might then result in reducing the TR4 binding to the TR4 response element (TR4RE) on the 5' promoter region of POMC. Results from in vivo mouse model also revealed that oral bexarotene administration markedly suppressed ACTH-secreting tumour growth, adrenal enlargement and the secretion of ACTH and corticosterone in mice with already established tumours. Together, these results suggest that bexarotene may be developed as a potential novel therapeutic drug to better suppress Cushing's disease.

Involvement of histone deacetylase 1/2 in adrenocorticotropic hormone synthesis and proliferation of corticotroph tumor AtT-20 cells.

Cushing's disease is mainly caused by autonomous production of adrenocorticotropic hormone (ACTH) from pituitary adenomas. In our previous study, a histone deacetylase (HDAC) inhibitor, trichostatin A, inhibited cell proliferation and ACTH production via decreased pituitary tumor-transforming gene 1 (PTTG1) in AtT-20 mouse corticotroph tumor cells. In the present study, we examined the effects of romidepsin, a potent and selective HDAC1/2 inhibitor, on cell proliferation and ACTH synthesis. To elucidate further potential mechanisms of romidepsin, we examined the effects of HDAC1/2 on proopiomelanocortin (Pomc) and Pttg1 mRNA levels and cell proliferation. Small interfering RNA-mediated knockdown was used to decrease HDAC1 or 2. Romidepsin treatment decreased Pomc and Pttg1 mRNA levels, and cell proliferation. The drug also increased Hdac1 and decreased Hdac2 mRNA levels. Hdac1 knockdown decreased basal Pttg1 mRNA levels and cell proliferation, but not Pomc mRNA levels. Romidepsin treatment decreases ACTH synthesis in corticotroph tumor cells. Romidepsin suppresses cell proliferation via PTTG1. HDAC1 is also involved in the proliferation of corticotroph cells via PTTG1.

The Mechanisms Underlying Autonomous Adrenocorticotropic Hormone Secretion in Cushing's Disease.

Cushing's disease caused due to adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas (ACTHomas) leads to hypercortisolemia, resulting in increased morbidity and mortality. Autonomous ACTH secretion is attributed to the impaired glucocorticoid negative feedback (glucocorticoid resistance) response. Interestingly, other conditions, such as ectopic ACTH syndrome (EAS) and non-neoplastic hypercortisolemia (NNH, also known as pseudo-Cushing's syndrome) also exhibit glucocorticoid resistance. Therefore, to differentiate between these conditions, several dynamic tests, including those with desmopressin (DDAVP), corticotrophin-releasing hormone (CRH), and Dex/CRH have been developed. In normal pituitary corticotrophs, ACTH synthesis and secretion are regulated mainly by CRH and glucocorticoids, which are the ACTH secretion-stimulating and -suppressing factors, respectively. These factors regulate ACTH synthesis and secretion through genomic and non-genomic mechanisms. Conversely, glucocorticoid negative feedback is impaired in ACTHomas, which could be due to the overexpression of 11ß-HSD2, HSP90, or TR4, or loss of expression of CABLES1 or nuclear BRG1 proteins. Genetic analysis has indicated the involvement of several genes in the etiology of ACTHomas, including USP8, USP48, BRAF, and TP53. However, the association between glucocorticoid resistance and these genes remains unclear. Here, we review the clinical aspects and molecular mechanisms of ACTHomas and compare them to those of other related conditions.

Cranial irradiation alters neuroinflammation and neural proliferation in the pituitary gland and induces late-onset hormone deficiency.

Cranial radiotherapy induces endocrine disorders and reproductive abnormalities, particularly in long-term female cancer survivors, and this might in part be caused by injury to the pituitary gland, but the underlying mechanisms are unknown. The aim of this study was to investigate the influence of cranial irradiation on the pituitary gland and related endocrine function. Female Wistar rat pups on postnatal day 11 were subjected to a single dose of 6 Gy whole-head irradiation, and hormone levels and organ structure in the reproductive system were examined at 20 weeks after irradiation. We found that brain irradiation reduced cell proliferation and induced persistent inflammation in the pituitary gland. The whole transcriptome analysis of the pituitary gland revealed that apoptosis and inflammation-related pathways were up-regulated after irradiation. In addition, irradiation led to significantly decreased levels of the pituitary hormones, growth hormone, adrenocorticotropic hormone, thyroid-stimulating hormone and the reproductive hormones testosterone and progesterone. To conclude, brain radiation induces reduction of pituitary and reproduction-related hormone secretion, this may due to reduced cell proliferation and increased pituitary inflammation after irradiation. Our results thus provide additional insight into the molecular mechanisms underlying complications after head irradiation and contribute to the discovery of preventive and therapeutic strategies related to brain injury following irradiation.

Cloning, expression, and purification of porcine adrenocorticotropic hormone in Escherichia coli.

Adrenocorticotropic hormone (ACTH) is an old medicine derived from porcine pituitary gland that has been marketed for more than 60 years. In this study, we present a recombinant approach to produce ACTH in Escherichia coli (E. coli). The SUMO-tagged fusion protein was cloned and expressed after induction with isopropyl-ß-d-thiogalactopyranoside (IPTG) at 25 °C for 8 h. The fusion protein was extracted and purified by anion exchange chromatography, and the SUMO tag was subsequently removed by digestion with ubiquitin-like protease 1 (ULP1). Approximately 95.3 mg of recombinant ACTH with 94.2% purity was obtained after cation exchange purification performed on a 5 mL column, from 286 mL fermentation broth based on the amount of pellets homogenized. The molecular mass of the recombinant ACTH was confirmed by mass spectrometry to equal 4567.32 Da.

Ectopic ACTH Secretion Secondary to Metastatic Acinic Cell Carcinoma of the Parotid Gland: A Case Report and Review of Current Evidence for Systemic Therapy.

Acinic cell carcinoma is a rare, typically indolent, neoplasm that arises in the salivary glands. Metastatic disease is uncommon, occurring in around 10% of cases. We report the case of a 46-year-old male in whom the first sign of disseminated disease was increased skin pigmentation due to paraneoplastic Cushing's syndrome. He underwent 3 cycles of chemotherapy with carboplatin and paclitaxel with no symptomatic improvement and a mixed response on imaging. There is no evidence that systemic therapy prolongs survival in metastatic acinic cell carcinoma, and we lack a consensus as to which treatment options are most beneficial. A summary of published evidence regarding choice of palliative chemotherapy regimens and response is discussed in relation to the case.

Effects of epigenetic pathway inhibitors on corticotroph tumour AtT20 cells.

Medical treatments for corticotrophinomas are limited, and we therefore investigated the effects of epigenetic modulators, a new class of anti-tumour drugs, on the murine adrenocorticotropic hormone (ACTH)-secreting corticotrophinoma cell line AtT20. We found that AtT20 cells express members of the bromo and extra-terminal (BET) protein family, which bind acetylated histones, and therefore, studied the anti-proliferative and pro-apoptotic effects of two BET inhibitors, referred to as (+)-JQ1 (JQ1) and PFI-1, using CellTiter Blue and Caspase Glo assays, respectively. JQ1 and PFI-1 significantly decreased proliferation by 95% (P < 0.0005) and 43% (P < 0.0005), respectively, but only JQ1 significantly increased apoptosis by >50-fold (P < 0.0005), when compared to untreated control cells. The anti-proliferative effects of JQ1 and PFI-1 remained for 96 h after removal of the respective compound. JQ1, but not PFI-1, affected the cell cycle, as assessed by propidium iodide staining and flow cytometry, and resulted in a higher number of AtT20 cells in the sub G1 phase. RNA-sequence analysis, which was confirmed by qRT-PCR and Western blot analyses, revealed that JQ1 treatment significantly altered expression of genes involved in apoptosis, such as NFκB, and the somatostatin receptor 2 (SSTR2) anti-proliferative signalling pathway, including SSTR2. JQ1 treatment also significantly reduced transcription and protein expression of the ACTH precursor pro-opiomelanocortin (POMC) and ACTH secretion by AtT20 cells. Thus, JQ1 treatment has anti-proliferative and pro-apoptotic effects on AtT20 cells and reduces ACTH secretion, thereby indicating that BET inhibition may provide a novel approach for treatment of corticotrophinomas.

Ectopic ACTH Production and Cushing's Syndrome in a Patient with Parotid Acinic Cell Carcinoma with High-Grade Transformation: Tumor Context and Clinical Implications.

We report a rare case of Cushing's syndrome in a 59-year-old man who initially presented with concurrent acinic cell carcinoma of the parotid with high-grade transformation and co-existing papillary and medullary thyroid carcinomas, without noticeable cushinoid symptoms. Six-months later, he developed clinical features of Cushing's syndrome which coincided with disease progression in the form of lung metastasis and mediastinal lymphadenopathy. Ectopic adrenocorticotropic hormone (ACTH) production and protein expression was limited to the high-grade transformed component of acinic cell carcinoma and in the lymph node metastasis, and was absent in the conventional acinic cell carcinoma as well as in the papillary and medullary thyroid carcinoma. He received adjuvant chemotherapy and supportive management with interval improvement for 8 months followed by disease progression with increasing serum cortisol levels and bone metastasis. He was offered palliative chemotherapy, however, declined further therapy and was lost to follow up. We discussed clinical and pathologic implications of ectopic ACTH production associated with acinic carcinoma and also reviewed the literature of this rare paraneoplastic syndrome.

General anesthesia combined with epidural anesthesia maintaining appropriate anesthesia depth may protect excessive production of inflammatory cytokines and stress hormones in colon cancer patients during and after surgery.

The purpose of this study was to investigate the influences of varied anesthetic methods and depths on inflammatory cytokines and stress hormone levels in radical operation among colon cancer patients during perioperative period.A total of 120 patients were collected in the study and randomly divided into 4 groups, A: general anesthesia + Narcotrend D1, B: general anesthesia + Narcotrend D2, C: general anesthesia + epidural anesthesia + Narcotrend D1, D: general anesthesia + epidural anesthesia + Narcotrend D2. The levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-10, cortisol (Cor), adrenocorticotropic hormone (ACTH), and endothelin-1 (ET-1) were measured adopting commercial kits before anesthesia (T0), 4 hours after surgery (T1), 24 hours after surgery (T2), and 72 hours after surgery (T3).There was no significant difference in basic clinical characteristics among the groups. In comparison with group A, B and C, group D showed significantly lower levels of TNF-α, IL-6, IL-10, Cor, ACTH, and ET-1 at T1 and T2 (all, P < .05). Significantly higher levels of TNF-α, IL-6, IL-10, Cor, and ACTH were detected at T1 and T2 than those at T0 (all, P < .05), whereas, at T3, the levels of inflammatory cytokines and stress hormones were all decreased near to preoperation ones.General anesthesia combined with epidural anesthesia at Narcotrend D2 depth plays an important role in reducing immune and stress response in patients with colon cancer from surgery to 24 hours after surgery.

Acute Liver Failure Due to Severe Hepatic Metastasis of Small-cell Lung Cancer Producing Adrenocorticotropic Hormone Complicating Ectopic Cushing Syndrome.

A 72-year-old man was admitted to a general hospital with progressive liver dysfunction, hypokalemia, hyperglycemia, and nodules in the lung and liver and then transferred to our institution on the seventh hospital day. Plasma levels of adrenocorticotropic hormone (ACTH), cortisol, and neuron-specific enolase concentrations were extremely high. He developed acute liver failure, his consciousness and general condition deteriorated rapidly, and he died on Day 11. At the postmortem examination, he was found to have extensive metastases from small-cell lung cancer, including advanced hepatic metastases. This is the first reported case of acute liver failure caused by metastases derived from an ACTH-producing pulmonary small-cell carcinoma.

Inhibition of Heat Shock Factor 1 Enhances Repressive Molecular Mechanisms on the POMC Promoter.

BACKGROUND: Cushing's disease (CD) is caused by adrenocorticotropic hormone (ACTH)-secreting pituitary tumours. They express high levels of heat shock protein 90 and heat shock factor 1 (HSF1) in comparison to the normal tissue counterpart, indicating activated cellular stress. AIMS: Our objectives were: (1) to correlate HSF1 expression with clinical features and hormonal/radiological findings of CD, and (2) to investigate the effects of HSF1 inhibition as a target for CD treatment. PATIENTS/METHODS: We examined the expression of total and pSer326HSF1 (marker for its transcriptional activation) by Western blot on eight human CD tumours and compared to the HSF1 status of normal pituitary. We screened a cohort of 45 patients with CD for HSF1 by immunohistochemistry and correlated the HSF1 immunoreactivity score with the available clinical data. We evaluated the effects of HSF1 silencing with RNA interference and the HSF1 inhibitor KRIBB11 in AtT-20 cells and four primary cultures of human corticotroph tumours. RESULTS: We show that HSF1 protein is highly expressed and transcriptionally active in CD tumours in comparison to normal pituitary. The immunoreactivity score for HSF1 did not correlate with the typical clinical features of the disease. HSF1 inhibition reduced proopiomelanocortin (Pomc) transcription in AtT-20 cells. The HSF1 inhibitor KRIBB11 suppressed ACTH synthesis from 75% of human CD tumours in primary cell culture. This inhibitory action on Pomc transcription was mediated by increased glucocorticoid receptor and suppressed Nurr77/Nurr1 and AP-1 transcriptional activities. CONCLUSIONS: These data show that HSF1 regulates POMC transcription. Pharmacological targeting of HSF1 may be a promising treatment option for the control of excess ACTH secretion in CD.

Triple negative breast cancer with ACTH-dependent Cushing's syndrome - case report.

INTRODUCTION: Endocrine and metabolic paraneoplastic syndromes in the course of malignant tumors result from ectopic production of hormones or hormone precursors in tumor cells. Production of hormones by endocrine tumors is relatively frequent, while such production by adenocarcinoma cells is definitely rare. The study presents a case of triple-negative invasive breast cancer, with the ectopic secretion of ACTH (adrenocorticotropic hormone), which provokes serious metabolic disorders. MATERIALS AND METHODS: The patient was admitted to hospital with symptoms of Cushing`s syndrome. Diagnostic tests revealed that the cause of metabolic disorders was breast cancer. After proper preparation, the patient was qualified for surgery. RESULTS: After the mastectomy, the patient's metabolism stabilized. The patient underwent adjuvant chemotherapy and radiotherapy. Four months after the last cycle of systemic treatment, cancer dissemination was found. The patient was treated with second-line chemotherapy, however, control CT revealed progression. The patient died 20 months after surgery and two months after the last cycle of chemotherapy. CONCLUSIONS: The case reported in this study - triple-negative invasive breast cancer, responsible for ectopic production of ACTH and causing Cushing's syndrome - is a rare phenomenon. Treatment of patients with breast cancer showing hormonal activity should not differ from general rules applied for breast cancer. However, due to accompanying metabolic disturbances, the patients need individualized oncological approach, precise diagnostic tests, and adequate preoperative preparation.

Ectopic Cushing Syndrome (ECS): 68Ga-DOTANOC PET/CT Localizes the Site of Ectopic Adrenocorticotropic Hormone Production.

Ectopic Cushing syndrome constitutes approximately 10% of all patients with Cushing syndrome. The clinical features of hypercortisolism result from elevated levels of adrenocorticotropic hormone produced by a tumor. The present case presented with clinical and biochemical parameters suggestive of Cushing syndrome with normal pituitary and adrenals on imaging. Ga-DOTANOC PET/CT done to localize an ectopic adrenocorticotropic hormone-producing tumor revealed metastatic medullary carcinoma of the thyroid as the culprit lesion.

T cell lymphoblastic lymphoma/leukemia within an adrenocorticotropic hormone and thyroid stimulating hormone positive pituitary adenoma: A cytohistological correlation emphasizing importance of intra-operative squash smear.

We present a rare case of primary pituitary T cell lymphoma/leukemia (T-LBL) in association with adrenocorticotropic hormone (ACTH) and thyroid stimulating hormone (TSH) expressing pituitary adenoma in a 55-year-old woman highlighting the importance of intra-operative squash smears examination. The patient presented with complaints of headache, diminution of vision and recent onset altered sensorium. MRI revealed a mass lesion in the sellar-suprasellar region with non-visualization of pituitary gland separately, extending to involve adjacent structures diagnosed as invasive pituitary macroadenoma. Intra-operative tissue was sent for squash smear examination. The cytology showed a tumor comprising of sheets of immature lymphoid cells intermixed with clusters of pituitary acinar cells with many mitoses and tingible body macrophages. A diagnosis of presence of immature lymphoid cells within the pituitary was offered and differentials of infiltration by lymphoma cells from systemic disease versus primary central nervous lymphoma-like lymphoma arising in the pituitary adenoma were considered. Later paraffin section examination and immunohistochemistry corroborated with the squash findings and a final diagnosis of primary pituitary T cell lymphoma/leukemia in association with ACTH and TSH expressing pituitary adenoma was made. To date, only six cases of primary pituitary T cell lymphomas, including three T-LBL cases, have been reported. This is the seventh case and first one additionally describing cytohistological correlation and importance of intra-operative cytology.

Giant Basal Cell Carcinomas Express Neuroactive Mediators and Show a High Growth Rate: A Case-Control Study and Meta-Analysis of Etiopathogenic and Prognostic Factors.

BACKGROUND: Giant basal cell carcinomas (GBCCs), (BCC ≥ 5 cm), are often painless, destructive tumors resulting from poorly understood patient neglect. OBJECTIVES: To elucidate etiopathogenic factors distinguishing GBCC from basal cell carcinoma (BCC) and identify predictors for disease-specific death (DSD). METHODS: Case-control study examining clinicopathologic and neuroactive factors (ß-endorphin, met-enkephalin, serotonin, adrenocorticotropic hormone, and neurofilament expression) in GBCC and BCC. Systematic literature review to determine DSD predictors. RESULTS: Thirteen GBCCs (11 patients) were compared with 26 BCCs (25 patients). GBCC significantly differed in size, disease duration, and outcomes; patients were significantly more likely to live alone, lack concern, and have alcoholism. GBCC significantly exhibited infiltrative/morpheic phenotypes, perineural invasion, ulceration, and faster growth. All neuromediators were similarly expressed. Adenoid phenotype was significantly more common in GBCC. Adenoid tumors expressed significantly more ß-endorphin (60% vs. 18%, P = 0.01) and serotonin (30% vs. 4%, P = 0.02). In meta-analysis (n ≤ 311: median age 68 years, disease duration 90 months, tumor diameter 8 cm, 18.4% disease-specific mortality), independent DSD predictors included tumor diameter (cm) (hazard ratio (HR): 1.12, P = 0.003), bone invasion (HR: 4.19, P = 0.015), brain invasion (HR: 8.23, P = 0.001), and distant metastases (HR: 14.48, P = 0.000). CONCLUSIONS: GBCC etiopathogenesis is multifactorial (ie, tumor biology, psychosocial factors). BCC production of paracrine neuromediators deserves further study.

Steroidogenic Factor 1, Pit-1, and Adrenocorticotropic Hormone: A Rational Starting Place for the Immunohistochemical Characterization of Pituitary Adenoma.

CONTEXT: -Pituitary adenoma classification is complex, and diagnostic strategies vary greatly from laboratory to laboratory. No optimal diagnostic algorithm has been defined. OBJECTIVE: -To develop a panel of immunohistochemical (IHC) stains that provides the optimal combination of cost, accuracy, and ease of use. DESIGN: -We examined 136 pituitary adenomas with stains of steroidogenic factor 1 (SF-1), Pit-1, anterior pituitary hormones, cytokeratin CAM5.2, and α subunit of human chorionic gonadotropin. Immunohistochemical staining was scored using the Allred system. Adenomas were assigned to a gold standard class based on IHC results and available clinical and serologic information. Correlation and cluster analyses were used to develop an algorithm for parsimoniously classifying adenomas. RESULTS: -The algorithm entailed a 1- or 2-step process: (1) a screening step consisting of IHC stains for SF-1, Pit-1, and adrenocorticotropic hormone; and (2) when screening IHC pattern and clinical history were not clearly gonadotrophic (SF-1 positive only), corticotrophic (adrenocorticotropic hormone positive only), or IHC null cell (negative-screening IHC), we subsequently used IHC for prolactin, growth hormone, thyroid-stimulating hormone, and cytokeratin CAM5.2. CONCLUSIONS: -Comparison between diagnoses generated by our algorithm and the gold standard diagnoses showed excellent agreement. When compared with a commonly used panel using 6 IHC for anterior pituitary hormones plus IHC for a low-molecular-weight cytokeratin in certain tumors, our algorithm uses approximately one-third fewer IHC stains and detects gonadotroph adenomas with greater sensitivity.