Simultaneous Detection of Primary Pulmonary Paraganglioma and a Mediastinal Mass: A Case Report

Abstract

Primary pulmonary paraganglioma (PPP) is an extremely rare neuroendocrine tumor. We present the case of a 71-year-old woman referred for dyspnea who was incidentally diagnosed with both a mediastinal mass and a pulmonary nodule. Chest computed tomography revealed an anterior mediastinal mass and a right-sided paracardiac pulmonary nodule. The mediastinal mass was excised via median sternotomy, and the pulmonary lesion was removed by wedge resection. Histopathological analysis identified the pulmonary lesion as a moderately differentiated paraganglioma, while the mediastinal mass consisted of ectopic thyroid tissue. Although the lesions were discovered simultaneously, their histopathological features were entirely unrelated, indicating a coincidental coexistence. Nevertheless, thorough histopathological examination is essential to exclude syndromic or metastatic associations. PPP should be considered in the differential diagnosis of pulmonary tumors, and surgical resection remains the mainstay of diagnosis and treatment.

Case report

A 71-year-old woman was referred to our clinic with a month-long history of dyspnea. Thoracic computed tomography (CT) revealed an anterior mediastinal mass approximately 55 mm in diameter (Fig. 1) and a paracardiac soft tissue density measuring 22 mm at its widest point (Fig. 2A, B). The differential diagnosis included lymphadenopathy and pulmonary nodule.

Fig. 1.

Chest computed tomography scan showing a well-defined anterior mediastinal mass measuring approximately 55 mm.

Fig. 2.

(A) Soft tissue density located in the paracardiac region, measuring 22 mm at its widest point (arrow). (B) Postoperative histopathological specimen confirming the diagnosis of moderately differentiated paraganglioma (arrow).

Median sternotomy was performed to remove the mediastinal mass. During surgical exploration, a pulmonary nodule was identified in the mediobasal segment of the right lower lobe and resected by wedge excision. Although both lesions were identified during the same procedure, histopathological analysis confirmed that they were unrelated. Examination showed that the anterior mediastinal mass consisted of ectopic thyroid tissue, whereas the pulmonary nodule was diagnosed as a moderately differentiated paraganglioma, according to the GAPP (Grading System for Adrenal Pheochromocytoma and Paraganglioma) classification.

Paragangliomas are rare neuroendocrine tumors originating from chromaffin cells of the sympathetic and parasympathetic ganglia [1]. They affect approximately 2 to 5 individuals per million annually [2]. Primary pulmonary paragangliomas (PPPs) are even rarer, comprising only 10%– 18% of all tumors derived from chromaffin tissue [3].

Postoperative serum catecholamine levels were within normal limits (adrenaline: 81.4 ng/L, noradrenaline: 555.7 ng/L). The patient was discharged following an uneventful postoperative course.

In our case, pathological findings definitively confirmed the diagnosis, with emphasis on specific histological and immunohistochemical features. Histopathological evaluation of the resected lung specimen showed tumor proliferation within the parenchyma, as illustrated in Fig. 3A. Hematoxylin and eosin-stained sections demonstrated tumor cells forming large nests and islands composed of cells with abundant eosinophilic cytoplasm and pleomorphic vesicular nuclei (left side of the image). Immunohistochemical analysis revealed diffuse chromogranin positivity in tumor cells (Fig. 3B) and widespread S100 positivity in sustentacular cells (Fig. 3C). Additionally, the absence of keratin expression helped distinguish paraganglioma from epithelial neuroendocrine tumors.

Fig. 3.

(A) Low-power view of the tumor (×100). The tumor is observed on the left side of the figure. (B) Chromogranin is diffusely positive in the tumor (×100). (C) S100 is positive in sustentacular cells (×100).

Written informed consent was obtained from the patient for the publication of this case report and its accompanying images.

Discussion

Paragangliomas are neuroendocrine tumors arising from neural crest cells of the parasympathetic ganglia. These slow-growing, painless masses predominantly occur in the head, neck, adrenal glands, and retroperitoneal regions. PPPs are exceedingly rare and often present a diagnostic challenge preoperatively, making pathological examination crucial for definitive diagnosis. Distinguishing PPPs from epithelial neuroendocrine tumors is vital due to their differing clinical, biochemical, and genetic characteristics [2,4].

The solitary form of PPP, as seen in our patient, is particularly uncommon [2]. The first documented case was reported by Heppleston [5] in 1958, and subsequent reports have remained scarce. Most PPPs are discovered incidentally during imaging studies performed for unrelated symptoms, as in our case. Clinical presentations are nonspecific, often including cough and chest pain [2].

While approximately 10% of PPPs exhibit malignant behavior, current histological or biochemical markers are insufficient for definitive malignancy diagnosis. Surgical resection, ranging from enucleation to lobectomy, remains the cornerstone of treatment. In our patient, wedge resection was sufficient for complete excision due to impaired respiratory function. CT and magnetic resonance imaging are important modalities for localizing and characterizing paragangliomas. Pulmonary paragangliomas typically appear as isodense or slightly hypodense on CT [2].

Radiologic evaluation suggested a paracardiac nodule or mediastinal lymphadenopathy as prediagnosis. Fine needle aspiration biopsy was not feasible due to the location of the nodule. Therefore, wedge resection was planned concurrently with mediastinal mass removal via sternotomy.

Other nuclear medicine imaging techniques, such as positron emission tomography (PET) and Ga-68 DOTATATE PET/CT, play important roles in evaluating pulmonary paragangliomas. These tumors highly express somatostatin receptors, making Ga-68 DOTATATE PET/CT particularly sensitive and specific for both localization and metastatic assessment [6]. Fluorodeoxyglucose-PET/CT is useful in evaluating aggressive or potentially malignant paragangliomas [7]. In our patient, no pathological findings were detected on Ga-68 scintigraphy performed after the diagnosis of paraganglioma.

This report highlights a rare case of primary pulmonary paraganglioma incidentally discovered during evaluation of a mediastinal mass. Histopathological examination revealed ectopic thyroid tissue in the mediastinal mass and confirmed the pulmonary nodule as paraganglioma. Despite simultaneous detection, their histopathological features were entirely unrelated. No direct embryological or pathological association between these 2 entities has been established in the literature [4,8]. Their coexistence appears coincidental; however, such synchronous findings should prompt thorough histopathological evaluation to exclude metastatic or syndromic associations.

Ectopic thyroid tissue in the anterior mediastinum is rare, resulting from aberrant migration during embryologic development [8]. Its coexistence with a primary pulmonary paraganglioma is uncommon, further highlighting the importance of comprehensive tissue analysis in patients with multiple thoracic lesions [9].

Although rare, PPP should be included in the differential diagnosis of pulmonary tumors. Surgical resection remains the primary treatment option. Immunohistochemical analysis and advanced imaging are essential for diagnosis and management. Further research is needed to elucidate the biological behavior and optimize the management of these rare tumors [2,4,10].