Embryonal rhabdomyosarcoma arising within the pituitary gland
Embryonal rhabdomyosarcoma is a primitive sarcoma that mimics the features of embryonic skeletal muscle. It most commonly affects the extracranial regions of the head including the soft tissues surrounding the orbit, nasopharynx, and nasal cavity. Nonorbital rhabdomyosarcomas can extend intracranially. However, only a few cases of primary intracranial rhabdomyosarcoma have been reported and only two cases have been reported originating primarily within the sella turcica (1, 3).
This patient was originally presumed to have juvenile-onset primary open-angle glaucoma due to his high intraocular pressure (2). However, his visual field defects progressed despite medical therapy and a brain MRI revealed the large intrasellar mass that was subsequently resected.
Histologically, the spindled and primitive tumor cells surrounded clusters of large epithelioid pituitary cells. The pituitary cells were diffusely positive for ACTH and negative for prolactin suggesting a proliferation of ACTH cells and possibly an associated ACTH-secreting pituitary adenoma within the rhabdomyosarcoma. The fact that these ACTH positive cells were present with each recurrence of the tumor further supports the idea that these pituitary cells represent an associated hyperplastic or neoplastic process.
Rhabdomyosarcomas are aggressive tumors, and the older age of this patient as well as the parameningeal growth, initial incomplete resection, and invasion of the sphenoid sinus suggest a poor survival rate. Thus, the patient was treated with an intensive combination of radiation and chemotherapy. Nine months after the patient's first excision, a follow-up PET-CT did not show any evidence of residual or recurrent tumor.
Contributed by Thor D. Stein, Yang-seok Chae, Namehee Won, Jeong-hyun Lee, and E. Tessa Hedley-Whyte