What is microglandular hyperplasia in an endocervical polyp in a female of reproductive age with abnormal vaginal bleeding?

What is Microglandular Hyperplasia in an Endocervical Polyp?

Microglandular hyperplasia (MGH) is a benign, hormone-responsive proliferation of endocervical glands that commonly presents as an endocervical polyp and requires no treatment beyond simple polypectomy, though it can mimic adenocarcinoma on both gross examination and histology. 1, 2

Histopathologic Definition

MGH is characterized by specific microscopic features that distinguish it from malignancy:

• Glandular architecture: The lesion consists of closely packed small glands with relatively uniform columnar or cuboidal nuclei 1
• Mitotic activity: Typically shows rare to absent mitoses, though unusual cases with 5-11 mitotic figures per 10 high-power fields have been documented without malignant behavior 1
• Growth patterns: Four histologic patterns exist—glandular, reticular, trabecular, and solid 2
• Cytologic features: Nuclei are relatively uniform without significant atypia, though rare variants may show mild to moderate nuclear atypia, hobnail cells, or signet ring cells 1

Clinical Context and Hormonal Association

MGH occurs predominantly in reproductive-age women with hormonal stimulation:

• Age range: Typically affects women aged 23-54 years (mean 37.2 years), though cases occur in postmenopausal women 1, 2
• Hormonal exposure: Significantly associated with progestin exposure—29.2% of MGH cases had progestin exposure versus 10.3% of controls (p=0.0014) 3
• Common triggers: Oral contraceptive use and pregnancy are frequently associated 2, 3
• Presentation: Most commonly presents as endocervical polyps in women with abnormal vaginal bleeding 1

Critical Differential Diagnosis

The most important distinction is separating MGH from endocervical or endometrial adenocarcinoma, as MGH can closely mimic malignancy:

Key Distinguishing Features:

Immunohistochemical profile (when diagnosis is uncertain):

• p16: Negative in MGH, typically positive in adenocarcinoma 1
• CEA (carcinoembryonic antigen): Negative in MGH, often positive in adenocarcinoma 1
• Vimentin: Negative in MGH 1
• Ki-67 proliferation index: Low (1-15%) in MGH 1

HPV status:

• MGH is consistently HPV-negative, whereas endocervical adenocarcinomas are frequently HPV-positive 1

KRAS mutation testing:

• Absent in all MGH cases (0/12), present in 60% of microglandular endometrial adenocarcinomas 4
• This molecular test offers additional discriminatory power when morphology is ambiguous 4

Clinical Behavior and Prognosis

MGH is entirely benign with excellent prognosis:

• Long-term follow-up (median 40.7 months, range 3-76.2 months) shows no progression to malignancy 1
• Even mitotically active variants (up to 11 mitoses/10 HPF) behave benignly without negative clinical impact 1
• Simple polypectomy is curative; no additional treatment is required 1, 2

Important Clinical Pitfalls

Avoid overdiagnosis in small biopsies:

• Mitotic activity alone should not trigger a cancer diagnosis in microglandular proliferations 1
• Inexperienced pathologists may misinterpret MGH as adenocarcinoma, leading to unnecessary aggressive treatment 3
• When morphology is concerning, use immunohistochemistry (p16, CEA, vimentin) and consider KRAS mutation testing before diagnosing malignancy 1, 4

Clinical correlation is essential:

• Always obtain history of hormonal medication use (oral contraceptives, progestin therapy) 3
• Document pregnancy status, as MGH is common in pregnant women 2
• Ensure adequate follow-up cytology if any diagnostic uncertainty exists, though MGH itself requires no specific surveillance beyond routine screening 1