Beyond Adenoma: Imaging Clues to Pituitary Involvement in Systemic Sarcoidosis

Introduction

Sarcoidosis is an idiopathic, multisystem granulomatous disorder characterised by non-caseating granulomas that most commonly affect the lungs and lymphatic system. 1 Central nervous system (CNS) involvement, termed neurosarcoidosis, is histologically present in up to 25% of systemic cases in postmortem studies, though it is clinically symptomatic in only about 5% of patients. 1 Isolated neurosarcoidosis without systemic disease is extremely rare, accounting for less than 1% of cases. 1,2

 Imaging evidence of CNS involvement is detected in nearly 10% of systemic cases. 1 Magnetic resonance imaging (MRI) is the modality of choice for assessing parenchymal, leptomeningeal, and hypothalamic– pituitary involvement. 1,3 Pituitary or infundibular involvement may manifest as cystic or solid enhancing lesions or thickening of the pituitary stalk, often mimicking neoplastic conditions like pituitary adenoma, particularly in the sellar and suprasellar regions. 1,4

Case Report

Case presentation

A middle-aged patient presented with a history of headache, nausea, fever, loss of appetite, and endocrine dysfunction (hypothyroidism). 1,2

Imaging findings

MRI of the brain revealed a large, oval, lobulated lesion centred in the sellar and suprasellar region. The lesion appeared isointense on T1- and T2-weighted images and demonstrated inhomogeneous post-contrast enhancement (Figure 1A–D). 1 The lesion abutted the optic chiasm with minimal associated oedema and showed minor extension into the right cavernous sinus.3,4 A key finding was the interval development of infundibular stalk thickening, measuring 8.5 mm (Figure 1B), which was not present on a prior MRI dated two months earlier (Figure 2A and B). 1 The posterior pituitary bright spot was normal in location and signal on T1-weighted images (Figure 1A). 1,4 

MRI findings: 

Cervical screening: Further screening revealed multiple enlarged, partly necrotic cervical lymph nodes on MRI (Figure 3A and B).2

CT/PET–CT findings: Positron emission tomography–computed tomography (PET–CT) confirmed metabolically active cervical lymphadenopathy (levels II–V), peripherally enhancing hepatic lesions in segments II, III, VII, and VIII, and pulmonary abnormalities including interlobular septal thickening and ground-glass opacities (Figures 4 and 5).

USG neck findings: Ultrasound of the neck corroborated these findings, showing conglomerate nodes with partial central necrosis (Figure 6A–D). 3 These multimodality findings, combined with systemic evaluation and histopathological confirmation, were consistent with neurosarcoidosis involving the pituitary gland. 

Discussion

Neurosarcoidosis of the hypothalamic-pituitary axis is rare and often diagnostically challenging. 1,2 In this case, the preservation of the posterior pituitary "bright spot" suggested sparing of the neurohypophysis, while the rapid interval thickening of the infundibular stalk served as a primary clue for a granulomatous process rather than a typical pituitary adenoma. 2 The differential diagnosis includes lymphocytic hypophysitis, lymphoma, metastasis, and germinoma. 2 

A multimodality approach was pivotal. 1,3 While MRI remains the gold standard for detailed CNS evaluation, PET–CT and ultrasound were essential for assessing the systemic disease burden and identifying accessible targets for tissue sampling. 1,4 This case highlights that integrating characteristic imaging patterns across modalities facilitates the differentiation of neurosarcoidosis from neoplastic conditions, enabling the timely initiation of systemic therapy. 3,4 

Acknowledgements

I, Dr. Mohit H. Tamakuwala, would like to acknowledge Dr. Deepak Patkar (H.O.D, Department of Radiology) and Dr. Mitusha Verma (Consultant Radiologist) at Nanavati Max Super Speciality Hospital, Mumbai, for their guidance. We also thank the patient and family for their consent.