Hong Zheng, Xue Yang, Meili Zhang, Weiyi Chen
Acidophil stem cell-like pituitary neuroendocrine tumors are uncommon PIT1-lineage tumors with heterogeneous morphology and immunophenotypes. Their distinction from other PIT1-lineage tumors and from tumors with additional gonadotroph-lineage-marker expression remains challenging. We retrospectively analyzed three surgically resected acidophil stem cell-like PitNETs. Clinical, endocrine, radiological, operative, histological, immunohistochemical, and follow-up data were reviewed. In cases 2 and 3, spatially matched serial sections were used to assess the relationship between PIT1 and SF1 expression. All patients were male and aged 17-48 years. The tumors showed PIT1 and PRL expression with variable GH expression. Case 1 showed LH positivity but was SF1-negative. Cases 2 and 3 showed SF1 positivity but were negative for FSH and LH. Spatially matched serial sections in cases 2 and 3 demonstrated PIT1-positive and SF1-positive nuclei in morphologically corresponding tumor-cell areas across consecutive serial sections, supporting PIT1/SF1 lineage-marker co-expression. All tumors showed radiological and/or intraoperative evidence of local invasiveness. The Knosp grades were bilateral grade 3 in case 1, grade 4 in case 2, and grade 1 in case 3. Early postoperative MRI showed no visible residual tumor in all cases. At the last available MRI follow-up, no recurrence or progression was identified after 14.7, 51.3, and 57.6 months in cases 1, 2, and 3, respectively. Acidophil stem cell-like PitNETs may show heterogeneous PIT1/SF1 or LH lineage-marker expression. Spatially matched serial-section analysis supports PIT1/SF1 co-expression in a subset of tumors; however, the biological significance and classification implications of this pattern require further study. Integrated interpretation of morphology, transcription factors, hormones, cytokeratin pattern, endocrine findings, radiological invasiveness, and longitudinal follow-up is essential.