Foreign body granuloma mimicking pituitary adenoma: Case report and literature review

Abstract

Background:

Foreign body granuloma of the pituitary gland is an exceptionally rare inflammatory lesion that may mimic recurrent adenoma on neuroimaging.

Case Description:

We report the case of a 44-year-old woman who previously underwent endonasal endoscopic surgery for a nonfunctioning pituitary adenoma and later developed a sellar mass secondary to a foreign body granulomatous reaction. Magnetic resonance imaging suggested tumor recurrence; however, gadolinium-enhanced imaging was not performed because of the patient’s known gadolinium allergy. Histopathological examination revealed xanthogranulomatous inflammation and a multinucleated giant-cell reaction to the suture material, without evidence of neoplastic recurrence.

Conclusion:

This case highlights the diagnostic challenges associated with postoperative sellar lesions and emphasizes the importance of histopathological confirmation in distinguishing foreign body granulomas from recurrent pituitary adenomas.

INTRODUCTION

Granulomatous inflammation of the pituitary gland is an uncommon entity that is often classified as autoimmune (lymphocytic or xanthogranulomatous hypophysitis) or secondary to infection, systemic disease, or prior surgical manipulation. Foreign body granulomas are exceedingly rare and usually represent a chronic inflammatory response to surgical materials, such as sutures or hemostatic agents. Because their clinical and radiological features resemble those of recurrent pituitary adenomas, accurate diagnosis relies on histopathological examination. Only a few cases have been described in the literature.

Clinical vignette

A woman with a previous history of pituitary apoplexy treated by endoscopic endonasal resection remained clinically stable for more than a decade, without evidence of residual or recurrent disease on serial imaging follow-up. She later presented with a persistent headache, and magnetic resonance imaging (MRI) demonstrated a new sellar lesion highly suggestive of tumor recurrence. However, histopathological analysis surprisingly revealed a foreign body granulomatous reaction without evidence of recurrent pituitary neuroendocrine tumor (PitNET).

CASE REPORT

A 44-year-old woman with a history of endonasal endoscopic surgery for a pituitary adenoma 12 years earlier underwent repeat pituitary MRI because of new-onset persistent headache.

At initial presentation, 12 years earlier, the patient developed a sudden-onset severe headache associated with acute adrenal insufficiency, a clinical presentation consistent with pituitary apoplexy. Initial pituitary MRI demonstrated a well-defined sellar lesion centered in the adenohypophysis, measuring approximately 1.3 cm in its greatest diameter, with suprasellar extension and mild compression of the optic chiasm. The lesion showed marked T1 hyperintensity and heterogeneous low signal intensity on T2-weighted images, findings suggestive of hemorrhagic and/or proteinaceous content, supporting the diagnosis of pituitary apoplexy. Mild deviation of the pituitary stalk to the left was observed [Figure 1a-c]. The patient underwent endonasal endoscopic surgery, and gross-total resection was achieved. Postoperative follow-up was performed at 3 and 6 months and annually thereafter, with no radiological evidence of residual or recurrent tumor [Figure 2a and b]. During follow-up, the patient required levothyroxine replacement therapy because of central hypothyroidism.

Figure 1:

(a) Sagittal T1-weighted magnetic resonance imaging (MRI) demonstrating a well-defined sellar lesion with marked intrinsic T1 hyperintensity and suprasellar extension. (b) Coronal T2-weighted MRI showing heterogeneous low T2 signal intensity within the lesion, with mild suprasellar extension and displacement of the pituitary stalk. (c) Sagittal postcontrast T1-weighted MRI demonstrating a sellar mass with suprasellar extension and compression of the optic chiasm, initially interpreted as a pituitary macroadenoma with hemorrhagic/apoplectic component.

Figure 2:

(a) Coronal T2-weighted magnetic resonance imaging (MRI) demonstrating postoperative changes in the sellar region without evidence of residual or recurrent lesion (b) Sagittal T1-weighted MRI showing postoperative remodeling of the sellar floor and decompression of the suprasellar cistern, with no radiological evidence of tumor recurrence.

Histopathological and immunohistochemical analysis confirmed a plurihormonal pituitary adenoma, with positive staining for prolactin, adrenocorticotropic hormone, thyroid-stimulating hormone, and luteinizing hormone and negative expression of Ki-67 and p53. Although transcription factor immunohistochemistry is currently recommended for PitNET classification according to the World Health Organization classification, these markers were not routinely available at the time of the patient’s initial surgery.

The current MRI [Figure 3a-d] revealed a nodular lesion measuring 1.3 × 1.1 × 1.0 cm in the right paramedian region of the adenohypophysis, with T1 hyperintensity and T2 hypointensity. The lesion extended toward the optic chiasm and displaced the pituitary stalk to the left, raising suspicion for tumor recurrence. Gadolinium-enhanced sequences were not obtained because of the patient’s known gadolinium allergy.

Figure 3:

(a) Coronal T1-weighted magnetic resonance imaging (MRI) showing a nodular lesion in the right paramedian region of the adenohypophysis, with intrinsic T1 hyperintensity. (b) Coronal T2-weighted MRI demonstrating corresponding T2 hypointensity of the lesion, with suprasellar extension toward the optic chiasm and deviation of the pituitary stalk to the left. (c) Sagittal T1-weighted MRI showing the craniocaudal extent of the sellar/suprasellar lesion. (d) Sagittal T2-weighted MRI confirming the hypointense signal pattern and relationship of the lesion with the optic chiasm.

A second endonasal endoscopic procedure was performed. Intraoperatively, a firm, well-circumscribed nodule was identified and completely removed. She developed severe epistaxis later that night and underwent emergency reoperation with hemostasis. She recovered from this complication without sequelae. During the following days, she developed transient diabetes insipidus and was discharged 5 days after admission.

Histopathological examination demonstrated pituitary tissue with a granulomatous inflammatory reaction. Foreign body-type multinucleated giant cells were identified, surrounded by chronic inflammatory infiltrate composed predominantly of lymphocytes and histiocytes. Adjacent fibrous tissue and areas of xanthogranulomatous inflammation were also observed [Figure 4]. These findings are consistent with a foreign body granuloma involving the pituitary region. No evidence of neoplastic recurrence was found. The patient’s postoperative course was uneventful, and there was no endocrinological dysfunction. The patient remained asymptomatic and free of recurrence at follow-up. Postoperative imaging confirmed complete resection of the lesion, without evidence of a residual sellar mass [Figure 5a-d].

Figure 4:

Histopathological findings of the sellar lesion. Hematoxylin and eosin staining showing a foreign body–type granulomatous inflammatory reaction, characterized by multinucleated giant cells surrounded by chronic inflammatory infiltrate and adjacent fibrous tissue. No evidence of neoplastic recurrence is observed. Original magnification: ×400.

Figure 5:

(a) Coronal T1-weighted magnetic resonance imaging (MRI) showing postoperative changes in the sellar region, with complete resection of the previously described lesion and no evidence of residual mass. (b) Coronal T2-weighted MRI confirming absence of residual sellar or suprasellar lesion, with decompression of the optic chiasm region. (c) Sagittal T1-weighted MRI demonstrating postoperative sellar changes after endonasal endoscopic resection, without evidence of residual nodular lesion. (d) Sagittal T2-weighted MRI showing preserved sellar anatomy and no residual compressive lesion.

DISCUSSION

Foreign body granuloma formation after pituitary surgery is an extremely rare complication, and its specific incidence in this surgical context has not yet been established. The available evidence derives from studies on cranial surgeries in general, which report an approximate incidence of 0.35%. In a retrospective review of 3,466 cranial procedures, 12 cases of granuloma were identified, with a median time to presentation of 13 months (range 1–545 months).[3] Three systematic reviews, each comprising approximately 100 cases and covering the period from 1965 to 2018, reported patient ages ranging from 1 to 77 years and symptom onset from as early as 2 weeks to as long as 45 years after surgery.[1,2,8] The results of these studies are summarized in Supplementary Table 1.

Foreign body granulomas often mimic tumor recurrence, meningioma,[4] or other inflammatory and infectious processes,[5,7,9-11] and histopathological confirmation is needed for a definitive diagnosis. The most frequently used materials include oxidized cellulose, sutures, gelfoam, methylmethacrylate, and bone wax, with 77% of cases resulting from the intentional retention of surgical materials.[10] Most patients are symptomatic, but outcomes are generally favorable following surgical removal, with complete resolution of symptoms in up to 100% of reported cases.[3]

Although no studies have focused exclusively on pituitary surgery, data from broader neurosurgical populations indicate that foreign body granulomas are very rare but clinically significant because of their potential to mimic tumor recurrence and cause diagnostic confusion. Therefore, this entity should be considered in the differential diagnosis of delayed sellar or parasellar lesions in patients with a history of pituitary surgery, particularly when hemostatic or synthetic materials are used intraoperatively.

Clinical manifestations

Headache is the most frequent symptom, ranging from intermittent to chronic, with episodes of acute exacerbation. The mass effect is consistently observed on neuroimaging, manifesting as sellar or suprasellar lesions with nonspecific features that closely mimic those of typical pituitary adenomas. Visual disturbances such as field defects, decreased visual acuity, or acute ophthalmoplegia have been described. From an endocrine standpoint, panhypopituitarism, selective hormonal deficiencies, and hyperprolactinemia secondary to pituitary stalk compression have been reported. These clinical manifestations are summarized in Supplementary Table 2.

Imaging findings

Imaging findings of foreign body granulomas in the pituitary region are exceedingly rare and sparsely documented in the literature. The available evidence consists of a single case report[6] describing a 24-year-old male who underwent partial resection of a suprasellar tumor followed by 54 Gy of radiotherapy and who presented with a recurrent lesion 1 year after surgery.

Contrast-enhanced computed tomography demonstrated an isodense suprasellar mass with homogeneous enhancement. MRI revealed low signal intensity on T1-weighted images and heterogeneous high signal intensity on T2-weighted sequences, suggesting a mixture of granulomatous and fibrous tissue possibly containing surgical foreign material (cotton fibers). The lesion extended into the right side of the third ventricle. These radiological findings were nonspecific, mimicking tumor recurrence, abscess, or cystic sellar lesions [Supplementary Table 3].

Pituitary foreign body granulomas lack distinctive imaging characteristics. Diagnosis depends on clinical and surgical correlation, particularly in patients with a history of prior pituitary or suprasellar surgery. Histopathological confirmation remains essential, as microscopic examination revealed cotton fibers within the granulomatous tissue. Although extremely uncommon, this entity should be considered in the differential diagnosis of recurrent or atypical sellar/suprasellar masses, especially in postoperative settings.

In the present case, the absence of radiological recurrence during more than a decade of follow-up after gross-total resection represented an atypical evolution for recurrent PitNET and retrospectively may be considered a clue suggesting an alternative postoperative lesion.

Learning points

• Foreign body granuloma should be considered in the differential diagnosis of delayed sellar lesions after transsphenoidal surgery

• Postoperative granulomatous lesions may radiologically mimic recurrent PitNET, particularly when associated with T1 hyperintensity and heterogeneous T2 signal changes

• A previous history of pituitary apoplexy and surgical manipulation may contribute to complex postoperative imaging findings

• Histopathological examination remains essential for definitive diagnosis, especially in atypical postoperative sellar lesions

• Long-term postoperative follow-up is important even after gross-total resection of pituitary adenomas

• Although transcription factor immunohistochemistry is currently recommended for PitNET classification, older cases may lack these markers because they were not routinely available at that time.

CONCLUSION

Foreign body granuloma of the pituitary gland is an exceptionally rare postoperative complication that can clinically and radiologically mimic tumor recurrence. Awareness of this entity is essential to avoid misdiagnosis and unnecessary surgical interventions. Correlation of clinical history, prior surgical manipulation, and radiological findings should raise suspicion of this diagnosis, but definitive confirmation relies on histopathological examination. Complete surgical excision typically provides excellent outcomes, with low recurrence rates and symptom resolution. Broader recognition among neurosurgeons and pathologists will improve diagnostic accuracy and optimize the management of postoperative sellar lesions.

Ethical approval:

Institutional Review Board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given consent for their images and other clinical information to be reported in the journal. The patient understands that the patient’s names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The author(s) confirms that they have used artificial intelligence (AI)-assisted technology for language editing, grammar refinement, and formatting support during manuscript preparation.

Supplementary data available at:

https://doi.org/10.25259/SNI_536_2026

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