SAT-096 - A Case Report of A Silent, Densely Granulated Lactotroph Adenoma

Background: Silent pituitary adenomas (SPAs) are defined by immunohistochemical expression of pituitary hormones or lineage-specific transcription factors without clinical manifestations of hormone hypersecretion. SPAs account for ~ 10-20% of surgically resected assumed nonfunctioning pituitary adenomas (NFPAs). Silent lactotroph adenomas (SLA) are rare, though at autopsy, approximately 40% of incidental pituitary adenomas identified show prolactin immunoreactivity. Silent tumors demonstrate more aggressive biological behavior than their functioning counterparts, with larger size, greater invasiveness, and higher recurrence rates. Here is a clinical case of a rare densely granulated SLA. [1-5]

Case Presentation: We report a 47-year-old Male presenting with acute visual loss, cranial neuropathy. MRI revealed a 4.8-cm multilobulated sellar and suprasellar mass with erosion of the sella turcica, sphenoid sinus invasion, and optic chiasm and Circle of Willis compression. Preoperative laboratory evaluation showed mild hyperprolactinemia consistent with Stalk effect, suppressed gonadotropins and low ACTH without clinical features of hormone excess.

The patient underwent urgent endoscopic transsphenoidal resection. Histopathology showed a densely granulated lactotroph PitNET with strong PRL and estrogen receptor expression, scattered GH-positive cells, low Ki-67 ( < 1%), and absence of ACTH, TSH, LH, or FSH staining, consistent with an SLA. Postoperatively, serum PRL effectively normalized. The course was clinically complicated, and he subsequently developed a saddle pulmonary embolism, suffered pulseless electrical activity arrest, and expired.

Discussion: SLA are uncommon and may present with symptoms related to mass effect rather than endocrine syndromes. Retrospective surgical studies have found that ~ 2% of sellar lesions are silent prolactin-sensitive adenomas and densely granulated prolactinomas even less common (0.3%). Preoperative prolactin levels may falsely suggest a nonfunctioning lesion or Stalk effect only. An aggressive imaging pattern may raise concern. Recognition of prolactin immunopositivity is clinically relevant, as dopamine agonist therapy may offer a therapeutic option in cases of residual or recurrent disease. However, most patients with prolactin-producing adenomas without hyperprolactinemia demonstrate resistance to dopamine agonists. [6-8]

This case highlights the importance of comprehensive hormonal, repeat PRL, and transcription factor profiling in NFPAs to refine classification, guide prognosis, and inform targeted medical therapy if appropriate. This case adds to limited clinical descriptions of SLA. Artificial Intelligence was used to check grammar and assist in reducing original text to word count.

References: PMID: 30020466, 28821944, 32130815, 37097352, 33476035, 32818756, 17287410, 41140514

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