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Reassessment of Plurihormonal Pituitary Adenomas/PitNETs
B K Kleinschmidt-DeMasters1, Christie G Turin2
1Department of Pathology, Neurology, Neurosurgery.
The American Journal of Surgical Pathology
|September 5, 2024
Summary
Plurihormonal pituitary tumors are reclassified into two main types: immature PIT1-lineage and PIT1/SF1 co-expressing tumors. Preoperative features like size or invasiveness do not differentiate these pituitary tumor types; only immunohistochemistry confirms the diagnosis.
Area of Science:
- Endocrinology
- Neuro-oncology
- Pathology
Background:
- Plurihormonal pituitary tumors express multiple hormones/transcription factors.
- WHO 2022 classification includes mature PIT1-lineage, immature PIT1-lineage, and unusual plurihormonal types.
- Recent "somatogonatotroph"/"multilineage" tumors with PIT1/SF1 co-expression challenge existing classifications.
Purpose of the Study:
- To reclassify plurihormonal pituitary tumors based on updated immunohistochemistry (IHC) findings.
- To correlate tumor reclassification with clinical, neuroimaging, and endocrinological features.
- To refine the understanding and classification of complex pituitary neuroendocrine tumors.
Main Methods:
- Database search (2018-2023) for plurihormonal pituitary tumors.
- Immunohistochemistry (IHC) for pituitary hormones and transcription factors (PIT1, SF1).
- Correlation of IHC findings with clinical presentation, tumor size, invasiveness, and hormonal secretion.
Main Results:
- 22 cases identified (9 male, 13 female; mean age 51±16 years).
- Most common symptoms: headaches/vision changes (6/22) and acromegaly (5/22). All were macroadenomas (mean diameter 25±17mm), 50% with cavernous sinus invasion.
- Reclassification yielded predominantly immature PIT1-lineage (9/22) and PIT1/SF1 co-expressing tumors (12/22), with only one unusual plurihormonal tumor.
- PIT1/SF1 co-expressing tumors showed nearly exclusive immunopositivity for FSH/LH, distinguishing them from immature PIT1-lineage tumors.
Conclusions:
- The classification of plurihormonal pituitary tumors is refined, with PIT1/SF1 co-expressing tumors largely replacing the "mature plurihormonal" category.
- Tumor size, invasiveness, and clinical endocrinopathies do not reliably preoperatively distinguish PIT1/SF1 co-expressing from immature PIT1-lineage tumors.
- Comprehensive immunohistochemistry is essential for accurate preoperative and definitive classification of these pituitary neuroendocrine tumors.
