Collision tumor of the sellar region

Abstract

Objective To summarize clinical and pathological features, diagnosis and differential diagnosis, as well as treatment and prognosis through analyzing one case of collision tumor in the sellar region (pituitary adenoma combined with malignant triton tumor).  Methods and Results A 59-year-old male was admitted to hospital with decreased vision, vision field defect and dizziness. Head MRI demonstrated space-occupying lesion in the sellar region. Therefore, the patient underwent a transsphenoidal surgery with subtotal tumor resection. Three months later, the patient was admitted to hospital again with vision loss and headache. Head CT demonstrated space-occupying lesions in sellar/suprasellar region, therefore, the patient underwent saddle tumor resection. Histological findings revealed that the tumor was composed of two different types of tumors, one was pituitary adenoma with epithelial cells arranged in nest-like and trabecular pattern, and the other was diffused spindle cell tumor. The two tumors were distributed separately or mixed togenther. The morphology of spindle cell tumor was bland with scarce mitosis in the first surgery, whereas additional features including increased cell density, dark nuclei, frequent mitosis and scattering distributed rhabdomyoblasts were found in the second surgery. Immunohistochemically, the pituitary adenoma (epithelial cell region) cells were positive for cytokeratin 8 (CK8), chromogranin A (CgA), synaptophysin (Syn) and thyroid stimulating hormone (TSH), while the malignant triton tumor cells (spindle cell region) were positive for CD56, CD57, calretinin (CR) and focally positive for S-100 protein (S-100), desmin (Des) and myogenin. Ultrastructural findings revealed abundant rough endoplasmic reticules and secretary granules in the cytoplasm of pituitary adenoma cells, and discontinuous basal lamina located outside the spindle cell membrane. The final pathological diagnosis was sellar collision tumor (non-functional TSH adenoma combined with malignant triton tumor). The patient died 6 months after the second surgery.  Conclusions Collision tumor of the sellar region with pituitary adenoma and malignant triton tumor is a rare tumor which can hardly be diagnosed by clinical and neuroimaging examination. The diagnosis relies on morphological characteristics, immunophenotype and ultrastructural features. The prognosis of collision tumor with malignant triton tumor component is poor. DOI: 10.3969/j.issn.1672-6731.2017.11.009