A Rare Case of Sellar Mass Composed of Primary Leiomyosarcoma and Pituitary Adenoma

Background: Nonfunctioning pituitary adenomas (NFPAs) are most common pituitary tumors, and primary pituitary gland malignancies are extremely rare. Most malignant pituitary gland lesions metastasize from other sites. Primary malignant lesions, such as sarcomas, usually develop after radiotherapy or chemotherapy for other diseases. We report a rare case of primary sellar leiomyosarcoma (LMS) without prior therapy that arose concurrently with a pituitary adenoma. Clinical Case: A 56-year-old woman with ptosis of the right eye, headache, and progressive visual deficits visited our neurosurgery department. She had no medical history besides hypertension. Twelve months ago, she was referred to us because of decreased visual acuity and a 3.5×3.6-cm-sized pituitary mass detected on brain MRI. Normal pituitary functions with mild hyperprolactinemia suggested a nonfunctioning pituitary mass with stalk compression. After transsphenoidal surgery, histopathology revealed a pituitary adenoma; MRI immediately post-surgery revealed no grossly remnant lesion. However, during the current visit, sellar MRI revealed a re-growing mass in the pituitary fossa extending to the sphenoid sinus and compressing the optic chiasm with a suprasellar extension. Functional endoscopic sinus surgery was performed, and histopathology revealed a composite tumor, i.e., a mesenchymal tumor with a pituitary adenoma. On immunohistochemical staining, smooth muscle actin, synaptophysin, and chromagranin were positive; tumor cell mitosis was observed at 7/10 high-power fields. Finally, a composite tumor of myxoid leiomyosarcoma and pituitary adenoma was diagnosed. Hence, systemic chemotherapy with radiotherapy was planned for the remnant lesion. Hormonal replacement therapy with hydrocortisone and thyroxine was also started for subsequent hypopituitarism. Conclusion: NFPA is benign and has good prognosis if it is not grow in size or is completely resected. Conversely, primary sarcomas, such as LMS, show rapid extension and aggressive local invasion. Although their incidence is extremely rare, few primary pituitary sarcoma cases with or without pituitary adenoma have been reported. In the former case, initial diagnosis of pituitary adenoma may lead to delayed diagnosis of combined malignant lesions. Thus, clinicians should consider this possibility and high index of suspicion is required when diagnosing a pituitary mass.