Parasellar T2 dark sign on magnetic resonance imaging to differentiate lymphocytic hypophysitis from pituitary adenoma
- Department of Radiology, University Texas Southwestern, Dallas, Texas, United States
- Department of Radiology, University of Iowa, Iowa City, Iowa, United States.
Department of Radiology, University of Iowa, Iowa City, Iowa, United States.
DOI:10.25259/SNI_338_2020Copyright: © 2020 Surgical Neurology International This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.
How to cite this article: Amit Agarwal1, Girish Bathla2. Parasellar T2 dark sign on magnetic resonance imaging to differentiate lymphocytic hypophysitis from pituitary adenoma. 08-Aug-2020;11:239
How to cite this URL: Amit Agarwal1, Girish Bathla2. Parasellar T2 dark sign on magnetic resonance imaging to differentiate lymphocytic hypophysitis from pituitary adenoma. 08-Aug-2020;11:239. Available from: https://surgicalneurologyint.com/surgicalint-articles/10187/
Background: Pituitary adenomas are the most common sellar masses in adults with magnetic resonance imaging (MRI) being the imaging modality of choice. Inflammatory pituitary lesions such as lymphocytic hypophysitis (LH) can mimic pituitary macroadenoma on imaging and are often misdiagnosed as such. Although the imaging appearance on most of the sequences on MRI has similar findings, LH has a characteristic dark signal on T2 images (called dark T2 sign) which can be very helpful to reliably differentiate the two conditions.
Case Description: A 68-year-old woman diagnosed with a “pituitary mass” on the MR study done at an outside facility was referred to our neurosurgery department. The case was discussed at our multidisciplinary tumor board, where the possibility of an inflammatory condition mimicking tumor was considered, given the very dark signal on T2-weighted sequences. Transsphenoidal endoscopic biopsy revealed a firm rubbery mass, which histopathology demonstrated fibrous connective tissue with inflammatory cells consistent with LH.
Conclusion: Dark T2 signal on MR imaging can be very helpful in demarcating inflammatory pituitary conditions like LH from pituitary macroadenomas.
Keywords: Lymphocytic hypophysitis, Magnetic resonance imaging, Pituitary adenoma, Sella, T2 dark sign
Pituitary adenomas are the most common sellar masses in adults with MR imaging being vital in diagnosis, pre-operative evaluation and post-operative follow-up. Inflammatory pituitary lesions such as lymphocytic hypophysitis (LH) can mimic pituitary macroadenomas on imaging and are often misdiagnosed as such. Although LH classically involves the infundibulum, involvement of the gland itself is not uncommon. However, glandular involvement in LH can appear very similar to pituitary adenoma on most of the MRI sequences. Inflammatory pseudotumors, like LH, however has a characteristic dark signal on T2 images (called dark T2 sign) due to the high lymphocytic and fibrotic contents. This sign is very helpful to differentiate the two conditions.
The patient is a 68-year-old woman who noted excessive thirst and dryness, along with progressive fatigue for 3–6 months. Endocrine laboratory evaluation revealed that her morning cortisol was low (3 ug/dl) with decreased ACTH. This prompted further evaluation with magnetic resonance imaging (MRI) of the pituitary gland, at an outside facility. The scan was interpreted with a final diagnosis of pituitary mass and presumably macroadenoma. She was referred to our University Hospital for further management. The patient’s MRI scan was subsequently discussed at our multidisciplinary tumor board. MRI study revealed a large sellar-parasellar enhancing mass- like lesion with the involvement of bilateral cavernous sinuses and encasement of the cavernous carotid arteries, along with thickening of the infundibulum [
Lymphocytic hypophysitis: coronal T1 postcontrast MR images reveals an enhancing infiltrative sellar-parasellar lesion (a and b) involving bilateral cavernous sinuses with thickening of the infundibulum (b – white arrow). Corresponding T2 coronal images (c and d) show a very low/dark signal within the soft- tissue component (black arrows). There is marked enlargement of the cavernous sinuses with encasement of the cavernous carotid arteries. No significant vascular narrowing noted.
The sella was exposed through an endoscopic transsphenoidal approach, and the dura was then opened using an arachnoid knife in a cruciate fashion. A firm rubbery mass was noted and multiple specimens were taken for frozen and permanent pathology. Frozen section demonstrated fibrous connective tissue with inflammatory cells. The final pathology revealed fragments of dense, fibrous connective tissue containing T lymphocytes, and histiocytes [
LH is an uncommon autoimmune inflammatory condition of the pituitary gland with lymphocytic infiltration, glandular tissue destruction, and varying degree of endocrine dysfunction. The inflammatory process can involve the entire pituitary gland, infundibulum, and the parasellar structures, including the cavernous sinus. The diagnosis of LH is made using clinical, imaging, and laboratory findings. MRI is the imaging modality of choice for suspected central nervous system involvement in LH. The MR imaging findings in LH are, however, variable ranging from subtle thickening of the pituitary infundibulum to large enhancing masses mimicking neoplastic conditions.[
Lymphocytic hypophysitis versus pituitary macroadenoma: coronal T2 images in the patient with lymphocytic hypophysitis (a) show characteristic dark signal seen within the inflammatory soft tissue (“parasellar dark T2 sign”). This is in sharp contrast with the heterogeneously bright T2 signal of pituitary macroadenomas with cystic areas (b) in a different patient.
Inflammatory intracranial lesions, like lymphocytic hypophysitis, can mimic neoplams on imaging. However, these lesions generally tend to have low signal on T2 images given the high lymphocytic and fibrotic components, which can be helpful in differentiation of these lesions from tumors.
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