Pituitary Disorders/Neuroendocrinology
Heng Yeh, MD (he/him/his)
Resident Physician
Memorial Healthcare System
Pembroke Pines, Florida, United States
A 50 year-old male with hypertension presented to the hospital for 3 weeks of worsening occipital headaches, diplopia but denied any visual field disturbances. He denied history of cancer or genetic syndromes in the family. On physical exam, bilateral pupils were equal and reactive to light with intact extraocular muscle movement. No other neurological signs were noticed. CT brain showed a 4.0 x 2.7 x 2.3 cm pituitary giant adenoma, invading the bilateral cavernous and left sphenoid sinuses. Blood works showed elevated prolactin ( >2000.00 ng/mL). Thyroid stimulating hormone(TSH), free T4, random cortisol level, Luteinizing hormone(LH), Follicle-stimulating hormone(FSH), Adrenocorticotropic hormone(ACTH), Growth hormone(GH), and Insulin-like Growth factor 1(IGF-1) were normal. [1] Cabergoline treatment was started and the prolactin level normalized after 20 days. However, his headache persisted with new bilateral papilledema and left eye palsy. A repeat MRI scan showed failure of tumor shrinkage with hemorrhagic necrosis. The tumor was resected and pathology revealed PitNET, positive for prolactin, Ki-67 labeling index < 1%, and an adjacent sarcoma with a shared mutation in PDGFRB. The sarcomatous tissue was positive for CD34 and vimentin, Ki-67 labeling index up to 60%, and negative for prolactin, TSH, GH, ACTH, FSH, and LH.
The transformation of a prolactinoma into a pituitary sarcoma is extremely rare and poorly understood. One case documents the spontaneous transformation of a previously treated adenoma into a sarcoma after only dopamine agonist therapy, without radiation. That case also reported the involvement of PDGFRB, which induces signaling of tumor microenvironment, including surrounding cells and matrix components, leading to sarcomatous transformation. Many other case studies have demonstrated that the sarcomatous transformation from pituitary adenoma is more likely when high doses of radiation are involved, but the lack of evidence like our own patient makes this case more interesting.
It is important to consider malignant tumors if the progress doesn’t correlate with the natural course, even if a patient has no known risk factors. If prolactinoma didn’t decrease in size despite improvement of prolactin level, other differentials should be considered.