Serous tumors
Serous borderline tumor / atypical proliferative serous tumor

Topic Completed: 1 June 2012

Minor changes: 11 January 2021

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PubMed search: ovarian serous borderline tumor

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Cite this page: Ehdaivand S. Serous borderline tumor / atypical proliferative serous tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/ovarytumorserousborderline.html. Accessed January 18th, 2021.
Definition / general
  • Serous tumors of low malignant potential, characterized by broad, branching papillae (hierarchical branching) focally covered by stratified epithelium with mild to moderate atypia with few mitoses

  • Müllerian inclusion cysts:
    • Usually considered benign inclusions, but may be bland-appearing metastases from serous borderline tumors (Am J Surg Pathol 2000;24:710)
    • Small cysts lined by bland, cuboidal-columnar serous-type epithelium with a simple architecture
    • Found in lymph nodes, pelvic peritoneum, omentum, bowel serosa, uterine serosa and parametrial connective tissues
    • Often multiple sites
Clinical features
  • Younger women, often pregnant
  • 10% have microinvasion, but rarely has malignant behavior
  • Bilateral in 25%
  • 5 year survival is 100% if confined to ovary; 90% if involves peritoneum
  • 5 year survival NOT equal to cure due to delayed recurrence or transformation to invasive carcinoma
  • Death due to bowel obstruction, ureteral obstruction, invasive carcinoma, sepsis and treatment complications
  • Rarely supradiaphragmatic nodal involvement (Am J Surg Pathol 2006;30:739)
Prognostic factors
Case reports
Gross description
  • Partially cystic with watery or mucinous cyst fluid with intracystic or surface soft white to tan cauliflower like papillary projections (usually more extensive and softer than papillae in benign serous papillary tumors)
  • Gross examination is not reliable to distinguish benign, borderline and malignant
Gross images

AFIP images

Polypoid excrescences and small papillae

Images hosted on other servers:

Bilateral tumors

Microscopic (histologic) description
  • Broad, branching papillae (hierarchical branching) focally covered by stratified epithelium with mild to moderate atypia with few mitoses
  • Some cells appear free floating as an artifact of sectioning
  • Epithelial cells may be columnar, polygonal or round with moderate to abundant eosinophilic cytoplasm
  • Cilia or surface snouts may be present
  • Intracystic spaces may be clear or contain mucin
  • Stroma is fibrous and edematous with variable psammoma bodies
  • Various patterns: cribriform, individual eosinophilic cells and cell clusters, simple and noncomplex branching papillae, inverted macropapillae and micropapillae
  • No stromal invasion; but may be associated with low-grade serous carcinoma, which does have destructive stromal invasion with an associated stromal reaction
  • Be careful not to confuse tangential sectioning with invasion
  • Pathology reports should describe surface involvement, microinvasion, micropapillary or cribriform growth, nodal metastases, invasive implants

  • Micropapillary architecture:
    • Epithelial cells surround prominent, nonbranching fibrous stalk and protrude radially as long, thin micropapillae without cores (Medusa head)

  • Lymph node involvement:
    • Present in up to 20% (when examined)
    • Metastases are present in sinusoidal spaces vs. parenchyma (benign rests)
    • Does not seem to alter prognosis (Am J Surg Pathol 1994;18:904)

  • Autoimplants:
    • Usually on surface or between exophytic surface tumor papillae
    • Single cells or glands and clusters of cells with abundant eosinophilic cytoplasm, mild-moderate atypia within fibroblastic stroma, stroma dominates over epithelium with "stuck-on" appearance
    • Associated with high stage tumors and noninvasive peritoneal implants
    • No apparent adverse prognostic value, so must distinguish from true stromal invasion (Am J Surg Pathol 2006;30:457)

  • Peritoneal implants:
    • Present in 30%
    • Most important prognostic indicator
    • Increased in tumors with surface involvement and micropapillary or cribriform architecture
    • Must separate from benign Müllerian or mesothelial inclusions
    • Two types: Invasive and Non-invasive (epithelial or desmoplastic)
      • Invasive implants: proliferative epithelium with infiltrating margin and desmoplastic stroma that resembles low-grade serous carcinoma
      • Non-invasive desmoplastic implants: gross - small tan-white lesions "plastered on" to serosal, omental, and peritoneal surfaces; micro - proliferative epithelium (including single cells) within reactive fibrous stroma, variable inflammation
      • Non-invasive epithelial implants: proliferative epithelium resembling borderline serous tumor within submesothelial invaginations and between adipose tissue lobules
    • Define as invasive if cytologic atypia (cells round up and have increased eosinophilic cytoplasm as in squamous cell carcinoma, round nuclei, prominent nucleoli), destructive stromal invasion, stromal reaction, capsular invasion; invasive nests have loss of calretinin+ mesothelial cells and loss of stromal CD34+ fibrocytes around the nests, with presence of alpha-smooth muscle actin+ myofibroblasts present as a stromal response (Mod Pathol 2006;19:364)
    • Define as borderline if typical histologic features (papillary, stratification, detached papillae), even if invasive implants exist
Microscopic (histologic) images

AFIP images

Lining cells stratified with cellular budding

Abundant eosinophilic cytoplasm

Abundant basophilic mucin fills the lumen of cyst

Tubule-like structures with orderly papillae

Large polypoid excrescences and many small papillae

Resembling desmoplastic peritoneal implant

With cribriform pattern

With micropapillary pattern

Tumor within a lymphatic of a lymph node

With microinvasion

Arising in lymph node

Images hosted on other servers:

Serous borderline tumor

Molecular / cytogenetics description
  • Serous borderline and low-grade invasive tumors express BRAF, KRAS, and occasional PIK3CA mutations; while high grade invasive carcinomas (grade 2 and 3) have different genetic aberrations, namely nonsynonymous p53 mutations, indicating that high grade invasive carcinomas do not arise from preexisting low-grade carcinoma or serous borderline tumors (Hum Pathol 2002;33:632, J Pathol 2012;226:413, Am J Surg Pathol 2009;33:1220)

Histopathology Ovary - Borderline ovarian tumor
Differential diagnosis
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