Macroadenoma - mostly in sphenoid
History of colorectal and breast cancer.
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A mass is present involving the right side of the pituitary fossa, adjacent sphenoid sinus, and bulging into possibly invades the right cavernous sinus. It is of intermediate T1 signal, demonstrates slightly heterogeneous contrast enhancement, and intermediate T2 signal, and is surrounded anteriorly by tract secretions within the sphenoid sinus. On dynamic contrast enhanced sequences normal pituitary enhancement is noted, and the mass demonstrates hypoenhancement compared to the remainder of the pituitary which appears to be abutting but somewhat separate.
CT (not shown) of the central base of skull demonstrates the bones to be destroyed, with communication of the right sided pituitary fossa with the right side of the sphenoid sinus. There is marked thinning/erosion of all surrounding bones with little if any bone remaining between the mass and the carotid inferolaterally, the optic canal anterosuperiorly, and the planum sphenoidale superiorly. No intracranial extension or dural enhancement is visible, and the mass does not extend into the left side of the sphenoid sinus. In some places bone appears somewhat remodelled rather than destroyed.
The remainder of the imaged brain (please note this study has been targeted to the pituitary, and as such the whole brain has not been imaged) appears unremarkable, other than an incidental cavum septum pellucidum and vergae.
Right-sided sphenoid sinus/pituitary mass. Somewhat unusual appearance and the differential is essentially between a metastasis or an unusual pituitary macroadenoma.
This was a challenging case. Destruction of bone rather than gentle remodelling, and the mass appearing to be separate from the pituitary on dynamic contrast enhanced sequence would favour the former (metastasis), especially as there is a history of dual malignancy (colorectal and breast), although no history of systemic metastases was provided. Having said that, pituitary macroadenomas are far more common, and can occasionally invade bone inferiorly without suprasellar extension. As such a definitive imaging diagnosis cannot be made.
The patient went on to have a transphenoidal resection.
The sections show a moderately cellular pituitary adenoma comprising trabeculae and nests, surrounded by vascularised stroma. The tumour cells have mildly enlarged round nuclei, finely granular chromatin and moderate amounts of eosinophilic cytoplasm. There are no atypical features. No normal anterior pituitary gland tissue is present. The tumour cells are negative for all the pituitary hormones. The Ki-67 index is 1%.
FINAL DIAGNOSIS: Null cell pituitary macroadenoma.
Again, the adage of "it's always a macroadenoma" proves to be correct in this instance. Macroadenomas are so common that they should be considered likely in all masses of the pituitary region unless an alternative diagnosis can be categorically be made (e.g. meningioma).