Giant Prolactinoma of Young Onset: A Clue to Diagnosis of MEN-1 Syndrome

An update on, and genetics of refractory adenomas of childhood

Pituitary adenomas in childhood tend to be more frequently due to germline genetic changes and are often diagnosed at late stages due to delayed recognition by pediatricians and other caretakers who are not familiar with this rare disease in childhood. As a result, often, pediatric pituitary adenomas are aggressive or remain refractory to treatment. In this review, we discuss germline genetic defects that account for the most common pediatric pituitary adenomas that are refractory to treatment. We also discuss some somatic genetic events, such as chromosomal copy number changes that characterize some of the most aggressive pituitary adenomas in childhood that end up being refractory to treatment.

Aggressive pituitary tumors in the young and elderly

Aggressive pituitary tumors (APTs) represent rare pituitary adenomas (PAs) with local invasion of surrounding tissues, increased risk for multiple recurrence, rapid tumor growth, or resistance to standard therapies. The most common APTs in children and adolescents are giant prolactinomas and somatotropinomas. Few cases of Crooke's cell adenomas, silent corticotroph adenomas and pituitary carcinomas have also been reported in the literature. Pediatric patients with APTs have higher risk of harboring germline genetic defects, most commonly in the MEN1 and AIP genes. Since certain genetic defects confer a more aggressive behavior to PAs, genetic testing should be considered in tumors with young onset and positive family history. The management of pediatric APTs involves usually a combination of standard therapies (surgical, medical, radiation). Newer agents, such as temozolomide, have been used in few cases of pediatric pituitary tumors with promising results. In the elderly, PAs are more commonly non-functioning. Their management often poses dilemmas given the coexistence of age-related comorbidities. However, standard surgical treatment and temozolomide seem to be safe and well tolerated in elderly patients.

Clinical management of difficult to treat macroprolactinomas

INTRODUCTION

Prolactinomas represent the most common pituitary adenomas encountered in the clinic. While a majority of these tumors will be successfully treated by dopamine agonist (DA) such as cabergoline, their management becomes problematic since a resistance to DA can occur and/or if the tumor displays features of aggressiveness, two conditions that are closely related.

AREAS COVERED

Epidemiology and medical treatment of prolactinomas; resistance to DA and molecular basis of DA-resistance; therapeutical alternatives in case of DA-resistant Prolactinomas and therapies in development; summarizing conclusions.

EXPERT OPINION

The management of DA-resistant prolactinomas requires a multidisciplinary approach by an expert team. Along with discussions about surgery with or without gamma knife radiosurgery, genetic screening for multiple endocrine neoplasia type 1 (MEN1) syndrome is actively discussed in a case-by-case approach. In case of surgery, a careful analysis of the tumor sample can provide information about its aggressivity potential according to recent criteria. Ultimately, temozolomide can be indicated if the tumor is rapidly growing and/or threatening for the patient.

Giant Prolactinoma Causing Hydrocephalus and Intracranial Hypertension as First Manifestations of Multiple Endocrine Neoplasia Type 1

Context: Overall, giant prolactinomas are rare tumors (4%), especially those larger than 60 mm (1%). Despite the predominance of macroadenoma documented in multiple endocrine neoplasia type 1 (MEN1)-related prolactinoma, only three giant prolactinoma cases were described so far (size > 40 mm and prolactin > 1,000 ng/mL). None of them was larger than 60 mm or presented hydrocephalus or intracranial hypertension (ICH) as initial manifestation of MEN1. Case Description: A 21-years-old man presented with ICH as the first clinical manifestation of MEN1. He harbored a MEN1 germline mutation but refused periodic vigilance after normal hormonal screening at age 14 years. During investigation, magnetic resonance imaging (MRI) of the skull showed an expansive sellar/parasellar lesion (75 × 44 × 36 mm) with moderate to severe supratentorial obstructive hydrocephalus and an extremely high serum prolactin (PRL) of 10,800 ng/mL, without combined hypersecretion of other pituitary hormones. He was diagnosed with giant prolactinoma, and cabergoline was initiated. The patient evolved with early improvement of clinical complaints for hydrocephalus and ICH and PRL reached normal values (11 ng/mL) in association with significant tumoral shrinkage after 18 months on cabergoline. After 2 months of cabergoline, cerebrospinal fluid leakage was diagnosed and corrective surgery was provided. The mean dose of cabergoline was 3 mg/week throughout treatment. Conclusion: We reported the first case with hydrocephalus and ICH as the initial clinical manifestation of a giant prolactinoma in MEN1. From our knowledge, this is the largest MEN1-related prolactinoma reported so far. Notably, all four MEN1-related giant prolactinomas cases reported were younger than 21 years strengthening the importance to routine MEN1 genetic testing for prolactinoma in this age group. Also, they all had initial effective response with dopamine agonist ensuring this drug as first-line treatment for MEN1-related giant prolactinoma. However, the scarce number of treated patients and progression of cabergoline resistance in two of them suggest strict surveillance.

Aggressive and Malignant Prolactinomas

Prolactin-secreting tumors (prolactinomas) represent the most common pituitary tumor type, accounting for 47-66% of functional pituitary tumors. Prolactinomas are usually benign and controllable tumors as they express abundant levels of dopamine type 2 receptor (D2), and can be treated with dopaminergic drugs, effectively reducing prolactin levels and tumor volume. However, a proportion of prolactinomas exhibit aggressive features (including invasiveness, relevant growth despite adequate dopamine agonist treatment, and recurrence potential) and few may exhibit metastasizing potential (carcinomas). In this context, the clinical, pathological, and molecular definitions of malignant and aggressive prolactinomas remain to be clearly defined, as primary prolactin-secreting carcinomas are similar to aggressive adenomas until the presence of metastases is detected. Indeed, standard molecular and histological analyses do not reflect differences between carcinomas and adenomas at a first glance and have limitations in prediction of the aggressive progression of prolactinomas, wherein the causes underlying the aggressive behavior remain unknown. Herein we present a comprehensive, multidisciplinary review of the most relevant epidemiological, clinical, pathological, genetic, biochemical, and molecular aspects of aggressive and malignant prolactinomas.