Tunnel Clusters
Brooke E. Howitt, MD
Marisa R. Nucci, MD
Key Facts
Clinical Issues
8% of all adult women
Typically asymptomatic
Incidental finding at hysterectomy or cone biopsy
Benign
Microscopic Pathology
Usually focal and superficial
If florid (rare), may mimic malignancy
Well-demarcated, lobular appearance
Lacks stromal response
Commonly a mixture of type A and type B patterns
Type A
Small, compact glands
Bland, basally located nuclei and apical mucinous cytoplasm
Type B
Cystically dilated mucin-filled glands
Flattened epithelial cells with bland ovoid nuclei
 Tunnel clusters are characteristically well-circumscribed, lobulated proliferations of mucin-filled glands. Note the lack of stromal reaction. |
 Tunnel clusters often show a mixture of glands lined by attenuated (type B)  and low cuboidal to columnar mucinous (type A)  epithelium with bland, basally located nuclei. |
TERMINOLOGY
Abbreviations
Tunnel clusters (TC)
Definitions
Benign proliferation of cervical glands (first described by Fluhmann in 1961)
ETIOLOGY/PATHOGENESIS
Unclear
May represent endocervical glands that become hyperplastic in response to hormonal influence
CLINICAL ISSUES
Epidemiology
Incidence
8% of all adult women
Multiparous > nulliparous
Possibly more common during pregnancy
May occur in postmenopausal women
Presentation
Typically asymptomatic
Incidental finding at hysterectomy or cone biopsy
