A 28-year-old nulliparous woman from Delhi presents with a 6-month history of amenorrhea and galactorrhea. Serum prolactin is elevated at 85 ng/mL (normal <25 ng/mL). MRI pituitary shows a 12 mm mass in the anterior pituitary with no suprasellar extension. On histopathology, the tumor consists of enlarged lactotroph cells with abundant cytoplasm and increased rough endoplasmic reticulum. Which type of cellular adaptation is most prominently demonstrated by the lactotroph cells in this prolactinoma?

Explanation

## Cellular Adaptation in Prolactinoma: Hypertrophy of Lactotroph Cells ### Pathophysiology of Prolactinoma Prolactinomas are benign neuroendocrine tumors arising from lactotroph cells of the anterior pituitary. The tumor cells exhibit: 1. **Increased cell size** (hypertrophy) — individual cells enlarge 2. **Enhanced protein synthetic machinery** — abundant rough ER and Golgi apparatus for prolactin synthesis and secretion 3. **Increased hormone production** — elevated serum prolactin ### Histopathologic Findings - **Enlarged cells** with abundant cytoplasm = hypertrophy - **Increased rough ER** = enhanced protein synthesis capacity (prolactin is a protein hormone) - **Prominent Golgi apparatus** = active hormone packaging and secretion - **Normal nuclear morphology** = preserved differentiation (not anaplasia) ### Key Point **Key Point:** Prolactinomas demonstrate **hypertrophy** (increase in individual cell size and synthetic capacity) rather than hyperplasia (increase in cell number). While the tumor does grow, the primary adaptive response of each lactotroph cell is enlargement to meet the demand for increased prolactin production. ### Comparison: Hyperplasia vs. Hypertrophy in Pituitary Adenomas | Feature | Hyperplasia | Hypertrophy | Prolactinoma | |---------|-------------|-------------|---------------| | **Cell number** | Increased | Normal/slightly ↑ | Increased (tumor growth) | | **Cell size** | Normal/small | Increased | **Increased** | | **Cytoplasm** | Scanty | Abundant | **Abundant** | | **Rough ER** | Normal | **Prominent** | **Prominent** | | **Hormone output** | ↑ (per cell) | **↑↑ (per cell)** | **↑↑** | ### Clinical Pearl The distinction is subtle: prolactinomas show both hyperplasia (increased number of lactotroph cells within the tumor) AND hypertrophy (each cell is enlarged with enhanced synthetic capacity). However, the **histopathologic hallmark** emphasized in pathology teaching is the **hypertrophy** of individual cells — the enlarged cytoplasm, abundant rough ER, and increased protein synthesis capacity. **High-Yield:** In neuroendocrine tumors: - **Hyperplasia** = increase in hormone-secreting cell population (e.g., parietal cell hyperplasia in Zollinger-Ellison syndrome) - **Hypertrophy** = increase in size and synthetic capacity of individual cells (e.g., lactotroph cells in prolactinoma) - **Adenoma** = benign neoplasm with both hyperplasia and hypertrophy of the cell population **Mnemonic:** **REPS** — Rough ER, Enlarged cells, Prolactin production, Secretory capacity = **Hypertrophy** in prolactinoma. [cite:Robbins 10e Ch 3]