Pituitary tumors are not brain tumors.

Panel A. A coronal MRI through the brain and the pituitary gland

From the desk of PWN cofounder Lewis S. Blevins, Jr. M D  – Social media has been a springboard for misinformation, and the spread of such, regarding a wide variety of topics. Politics. Sports. Education. Law. Medicine. I can’t think of a field or arena that has not been touched by this epidemic (pardon my use of the word in this era) of said misinformation. There are, of course, a lot of reasons behind this epidemic. Some are related to the genesis of misinformation while others are a direct result of its rapid proliferation and propagation through society.

Panel A. A coronal MRI through the brain and the pituitary gland

One of the topics of interest to us at Pituitary World News is this notion of pituitary adenomas being brain tumors. They’re not. And I’ll show you why in a moment. Yet, many firmly hold onto this belief that they’re brain tumors….and some seem to use this notion for secondary gain. Frankly, in this field, where many people we encounter haven’t heard of a pituitary tumor, it is our responsibility to educate family, friends, coworkers, and other contacts with accuracy and precision about these tumors. In this way, and only with this approach, will we be understood fully and recognized as truly advancing knowledge of pituitary disorders.  Truthfully, a pituitary tumor is no more a brain tumor than is a little wooden boat a yacht….or a pedal pusher go-cart a high-performance sports car….or a mound of dirt a mountain.

Panel B. The pituitary has been colored red and the brain is outlined in orange. Clearly, the anterior pituitary gland is not part of the brain.”

Why all the confusion in the first place? Well. Probably because neurosurgeons do pituitary surgery. But they also do peripheral nerve surgery. And spine surgery, too. Peripheral nerves and the spine are not brain either. The only reason neurosurgeons operate on the pituitary gland is because they always have. Mostly because it’s in the head. And near the brain. Truthfully, some ear, nose, and throat surgeons also operate on the pituitary and nearby structures. So it stands to reason that a pituitary tumor is not a brain tumor just because neurosurgeons operate on the gland. Yes. The anterior pituitary is a gland. An endocrine gland. Not brain.

The World Health Organization has always included pituitary tumors with other tumor types that affect the brain and meninges mostly because neurosurgeons operate on the pituitary gland. To my knowledge, they have never called it a brain tumor. Here is a link to the most recent update: Overview of the 2017 WHO Classification of Pituitary Tumors.  You will notice they do not refer to pituitary tumors as brain tumors in the manuscript.

A pituitary tumor is defined as a tumor from where it originates, the pituitary gland. So call it what it is. It’s not brain tissue. It is s tumor of your embryologic mouth. Yes. Your mouth! Perhaps we should call it an oral tumor?! I don’t like that so much, so let’s stick with pituitary.  The pituitary gland is actually developed from the embryologic tissues that form the hard palate or roof of your mouth. That’s not your brain. In the developing embryo, the outer covering develops into a neuroderm that becomes the brain and spinal cord. The ectoderm forms the skin and the entire gastrointestinal tract from mouth to anus.

“Dr. Rathke was an exceptional physician who studied developmental and comparative anatomy and biology.”

The primitive mouth or stomadeum is the tissue from which Rathke’s pouch develops. This pouch is flat tissue that grows upwards and then pinches off and develops into the anterior pituitary gland.

“An illustration from Rathke‘s original manuscript describing the embryology of the pituitary gland.”

A large number of genes, well over 25 that we know of, are expressed controlling every aspect of pituitary development from formation of the Rathke’s pouch, to transformation to glandular tissue, to development of stem cells and transition to the different hormone-producing cells including successful production and release of anterior pituitary hormones.

Mutations in many of these genes have been described in persons with various forms of hypopituitarism. Further, mutations in at least two of these genes have been associated with the development of Rathke’s cysts in mice.

It’s an amazing story and new knowledge is gained with each passing year. Here are some links for those of you who may be interested in learning more.

The artist‘s rendering shows the origination (stages A through E) of Rathke’s pouch from the embryological mouth, through successive stages of development, culminating in the mature pituitary gland.  The posterior pituitary is, in fact, an extension of the brain. Tumors of the posterior pituitary may be derived from different cell types but are still referred to as posterior pituitary tumors and not brain tumors.

 

The pituitary gland has come a long way. Early anatomists thought that its job was to produce snot, given its position above the sphenoid sinus cavity. They were certainly quite wrong! The pituitary has been called the “master gland.” Given the tissue of origin, its fantastical gene-controlled development, and the intricacies of its function, it deserves to not be considered a subject of the brain nor referred to as brain.” It stands alone, doing its job in conjunction with the brain and other glands. Elevate the pituitary to its rightful place and teach others about this marvelous gland.

Please help us spread the word about all things pituitary.

 

© 2021, Pituitary World News. All rights reserved.

2 COMMENTS

  1. It’s very debatable. In November 2018 Craniopharyngiomas were reclassified as malignant. . They can (and do) invade the 3rd ventricle of the brain. In my case I have hypothalamic damage, and damage to the optic nerve and trigeminal nerve… It’s not quite as simple as you make out.
    We have enough problems getting appropriate treatment and support without debates about how many angels are dancing on the head of a pin! We are operated on by teh same team as treat brain tumours, and treated using the same pathways (surgery & radiotherapy) – does it really matter?
    In fact, I was so careful of this distinction that I avoided seeking support when I was being treated – because I felt there were so many other so much more “deserving” than I was!! I was extremely ill as a result!! So I would STRONGLY urge others not to make these kinds of invidious comparisons.

  2. The issue of nomenclature and classification of pituitary tumors is debatable. The leading message of your article challenging the common belive the pit tumors are kind of brain tumors.

    I appreciate your arguments in number of points, but there is a bunch of facts that explain the commonly coined view.
    First, well known and highly influential institution in the US and worldwide The Central Brain Tumor Registry of the United States (CBTRUS) always accounted pit tumors into the primary brain tumors and other CNS tumors. The recent CBTRUS report (DOI: 10.1093/neuonc/noaa200 ) lists the pituitary and craniopharyngeal duct tumors as the second most common non-malignant brain tumors ( after meningioma), and the second most commonly reported histology – pituitary tumors 16.9% ( after meningioma 38 % and Gliblastoma 14,5%).

    The WHO Classifications of tumors of the Central Nervous System ( the so called blue books) with both previous editions ( 2007, 2016) included the category of sellar tumors listing Cranioppharyngiomas, Pituicytoma, Granular cell tumorof neurochypophysis, spindle cell oncocytomas.
    The most recent fifth ed. ( 2021) https://doi.org/10.1093/neuonc/noab106 of WHO Classification goes even further and includes pituitary adenomas and present the new term Pituitary neuroendocrine tumor (PitNET) proposed by the WHO endocrine group, which as they state will be further debated for the fifth-edition WHO classification of endocrine tumors.

    There are like 10-15 % of giant pituitarty adenomas which growth into cranial cavity and in number of cases invade cerebral meninges and the brain itself being in fact secondary brain tumors per se.

    The pituitary as you pointed is a endocrine gland, but you should add its very special type – of hybrid like gland – which can not work without cooperation with hypothalamus – the small but extremely important part of the brain.
    The pituitary is composed of few parts : the main part ( both lobes), pituitary stalk composed pituitary stem, neural lobe, median eminence which are included into the parts of the brain as the neurohypophysis. So the anatomical composition of the pituitary gland is also like hybrid brain /glandular/adenoid.

    The historical and traditional assignment of pituitary tumors to neurosurgery is not a matter of coincidence, the symptoms as well as the common secondary complications of tumor growth itself and surgery are of intracranial and neurological nature ( hypothalamic injury , hydrocephalus, blindness, intracranial haemorrhage) and are most often neurosurgical emergencies.

    You write the posterior pituitary is, in fact, an extension of the brain but the posterior pituitary tumors and not brain tumors. So the same can be said of pineal tumors or meningiomas which are “parts of brain” but are not the brain tumors in very narrow definition ( like gliomas or neurolnal tumors).
    In relation to topographical anatomy, the sella turcica is a part of the skull base, the structure has one of the most complex anatomical relations according to brain base, number of brain arteriesand veins and cranial nerves. The proper handling with those structures and even access to pituitary is mostly conjoined with brain surgery.
    In the recent decades we observe the blooming and significant development of the special field of brain surgery devoted to skull base pathologies (The Skull base surgery), and as there is a problem with naming the pituitary tumors kind of brain tumor, it is hard to deny the pituitary tumors are the most common benign skullbase tumors.

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