Ectopic pituitary adenoma in sphenoid sinus: a case presentation

Introduction

Pituitary adenomas are a group of tumors that originate from the pituitary gland, neurohypophysis, and ectopic pituitary cells. The majority of pituitary adenomas are benign and occur most frequently in the sellar region, with an equal incidence in both sexes (1). When a pituitary adenoma grows outside the sellar region such as in the sphenoid sinus, nasal cavity, and clivus region, they are considered ectopic pituitary adenomas (EPAs). Compared with pituitary adenomas, EPAs have the general clinical features of pituitary adenomas, but also present with different clinical symptoms due to the specificity of the growth site, such as dizziness and headache, epilepsy, motor neuron paralysis, enuresis, and endocrine disorders. In addition, EPAs are challenging to diagnose on imaging due to their specific growth site. In this paper, we report a case of EPA occurring in the sphenoid sinus and analyze and discuss it with related literature and cases.

Case presentation

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

A 50-year-old female patient had undergone cranial magnetic resonance imaging (MRI) examination at a local hospital two months prior due to dizziness, which revealed intracranial space-occupying lesions. She subsequently sought consultation from the Department of Neurosurgery at Jining No.1 People’s Hospital. Before surgery, the patient was in good general health and was not experiencing any discomfort. Laboratory tests indicated prolactin (PRL) level of 25.80 ng/mL (normal range 4.8–23.3 ng/mL), adrenocorticotropic hormone (ACTH) level of 6.89 pmol/L (AM 7:00–10:00 normal range 1.6–13.9 pmol/L), growth hormone (GH) level of 0.23 ng/mL (normal range 0.126–9.88 ng/mL), and thyroid stimulating hormone (TSH) level of 2.260 µIU/mL (normal range 0.75–5.6 µIU/mL). MRI examination of the pituitary gland revealed an irregular space-occupying lesion in the sphenoid sinus, with a slight hyperintense signal on T1-weighted imaging (T1WI) and an iso-signal on T2-weighted imaging (T2WI). After enhancement, the tumor showed mild inhomogeneous enhancement (Figure 1A-1C). A computed tomography (CT) examination revealed an abnormal density lesion in the sphenoid sinus. Additionally, there was bone destruction of the sellar bottom and clivus region, with partial bone resorption (Figure 1D). A neuroendoscopic operation was performed to remove a tumor in the sellar region through the nasal cavity. During the operation, it was observed that the tumor had already invaded the bone of the clivus region. The tumor had a grayish-white appearance, was soft and partially tough, and had a rich blood supply. The operation was successful, and the sample of grayish-white tissue was sent for examination. Immunohistochemistry showed that the tumor cells were positive for synaptophysin (syn) and focal positive for ACTH and pituitary transcription factor-1 (PIT-1), negative for follicle-stimulating hormone (FSH), luteinizing hormone (LH), PRL, TSH, estrogen receptor (ER), and Ki67 (+, 1%). Combined with the pathological (Figure 2) and immunohistochemical findings, EPA was considered.

Figure 1 Preoperative MRI and CT images of the tumor. (A) Sagittal position on T1WI, an irregular low-signal shadow (white arrow) could be observed in the sphenoid sinus. Blue arrow: pituitary gland. (B) Transverse position on T2WI, an irregular isointense shadow (white arrow) can be seen; (C) coronal position of T1 contrast enhancement. An irregular soft tissue mass (white arrow) was observed in the sphenoid sinus with mild enhancement (white arrow), with unclear boundary of the right sellar bottom, and pituitary gland located at the superior parts of the lesion. Yellow arrows: optic chiasm; blue arrow: pituitary gland; red arrow: infundibulum. (D) CT bone window scan showed the soft tissue shadow (white arrow) and bone destruction. MRI, magnetic resonance imaging; CT, computed tomography; T1WI, T1-weighted imaging; T2WI, T2-weighted imaging.

Figure 2 HE stain of the EPAs. (A) HE ×100, the tumor cells consisted of uniform, small, round cells arranged in nests under microscopy. (B) HE ×400, the tumor cells are separated by a network of slender blood vessels, the cells are rich in the cytoplasm and arranged in a nested, glandular pattern, and the nuclei have fine chromatin. HE, hematoxylin and eosin; EPAs, ectopic pituitary adenomas.

Discussion

EPAs are tumors that develop in pituitary tissue outside of the sellar region (2,3) and are a notably rare occurrence. As a subtype of pituitary adenoma, EPA shares common characteristics with pituitary adenomas, but also has unique features (4). For instance, pituitary adenomas are mostly microadenomas, whereas EPAs are mostly macroadenomas. Additionally, there is no significant gender difference in the incidence of pituitary adenomas, but the proportion of females is slightly higher than that of males in the incidence of EPA (1). It has been hypothesized that EPAs are associated with the migration of embryonic cells from Rathke’s pouch to the sellar turcica, and that the residual embryonic cells of this process might form tumors (5,6). Therefore, any site along the migration pathway may be the site of EPA. This is consistent with the favorable sites of pituitary adenomas in related studies. The most common locations of EPAs are the sphenoid sinus, clivus region, cavernous sinus, and nasopharynx (5,6). Related studies (4) have shown that the sphenoid sinus is the most common site of EPAs, accounting for approximately 34% of EPAs. There are also a few case reports of tumors located in the nasal cavity, supraorbital fissure, orbital cavity, maxillary sinus, and sieve sinus (7). A CT scan would reveal slight high or isodense areas, typically without calcification. The compression of the bone causes resorption of the adjacent sinus wall, resulting in thinning and localized destruction. According to MRI, T1WI exhibits a slightly low or equal signal, whereas T2WI exhibits an equal or slightly high signal (8). Some cases may also present with cystic degeneration, necrosis, or hemorrhage. The enhancement is of a mild to moderate degree and exhibits uneven characteristics. Clinical symptoms and signs of EPA are atypical, making it difficult for clinicians to diagnose and identify EPA. Despite the lack of specificity of clinical presentation, there are still some interesting clinical findings of EPAs. Campana et al. (3) found that parasellar EPAs have a high chance of violating bone, which may be related to the low proliferative activity. Zhu et al. (4) found that EPAs in the cavernous sinus and ACTH-secreting EPAs were commonly microadenoma. Most EPAs are functioning adenomas, and few are nonfunctioning adenomas. Functioning adenomas are classified based on the type of hormone secreted in excess, including ACTH-secreting adenomas, PRL-secreting adenomas, GH-secreting adenomas, and TSH-secreting adenomas. ACTH-secreting adenomas are the most common subtype. Patients with suprasellar EPAs are more likely to experience menstrual symptoms; patients with clival EPAs are more likely to suffer from headaches; nasopharyngeal EPAs more frequently present with nasal congestion. Clival tumors are most likely to secrete PRL; nasopharyngeal tumors are most likely to secrete TSH; sphenoid sinus tumors are most likely to produce ACTH (5). As a type of neuroendocrine tumor, the majority of EPAs are benign and have a good prognosis. The treatment of EPAs can be divided into surgery, medication, and radiotherapy. Surgery is an important treatment of EPAs and can solve the problem from the root. However, due to the specific location of tumors, it is difficult to operate and address the problem of tumor residue (1,3). Patients whose tumors cannot be completely removed or cannot be surgically resected can choose drug treatments, especially for patients with PRL-secreting adenomas. Common drugs include dopamine agonists and GH antagonists (6), which aim to reduce prolactin levels, relieve symptoms of endocrine disruption, and shrink tumors. Radiotherapy carries the risk of causing hypopituitarism and impaired brain function, and therefore is not the current treatment for EPAs, but is mainly used in patients with aggressive, malignant EPAs or those with postoperative recurrence. CT scans provide a unique advantage in observing bone damage caused by tumors, which can assist neurosurgeons in determining the invasiveness of the tumor and selecting appropriate surgical approaches and procedures. As pituitary adenomas are common intracranial tumors (4), the possibility of pituitary adenomas should also be considered when soft tissue lesions are found in anatomical locations where the pituitary gland has migrated during development, and provide appropriate guidance on imaging, clinical diagnosis, and differential diagnosis of pituitary adenomas.

Acknowledgments

Funding: None.

Footnote

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-1101/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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