Definition/General
Introduction:
Fallopian tube micropapillary carcinoma is a rare, aggressive variant of tubal adenocarcinoma characterized by micropapillary architecture without fibrovascular cores
It represents approximately 2-4% of all fallopian tube carcinomas
The tumor demonstrates small papillary tufts that lack central fibrovascular support
It shows aggressive biological behavior with high metastatic potential
The micropapillary pattern must comprise >50% of the tumor for diagnosis.
Origin:
Originates from the epithelial cells of the fallopian tube with loss of normal architectural organization
The micropapillary tufts result from cellular proliferation without stromal support
May develop from high-grade serous or conventional adenocarcinoma
The pattern reflects aggressive tumor biology
Associated with enhanced metastatic capability.
Classification:
WHO classification recognizes it as a morphological variant of high-grade adenocarcinoma
Micropapillary pattern must predominate (>50% of tumor)
High-grade carcinoma (Grade 3) in majority of cases
Distinguished from conventional papillary by absence of fibrovascular cores
May show mixed patterns with serous carcinoma
FIGO staging follows standard criteria.
Epidemiology:
Rare entity with limited case series reported (fewer than 80 cases)
Peak incidence in 6th-7th decades (similar to high-grade serous)
No specific racial predilection
Very aggressive behavior with poor prognosis
No established BRCA association (studies limited)
Advanced stage at presentation common
May be underrecognized due to morphological similarity to serous carcinoma.
Clinical Features
Presentation:
Rapidly growing pelvic mass with aggressive course
Severe pelvic pain and cramping
Heavy vaginal bleeding or postmenopausal bleeding
Abdominal distension and early satiety
Constitutional symptoms (weight loss, fatigue)
Ascites development early in course
Advanced stage at presentation (majority Stage III-IV).
Symptoms:
Severe, persistent pelvic pain
Heavy menstrual bleeding or postmenopausal bleeding
Abdominal fullness and bloating
Early satiety and nausea
Urinary frequency and urgency
Bowel symptoms (constipation, bloating)
Rapid symptom progression over weeks to months
Constitutional symptoms (fatigue, weight loss).
Risk Factors:
Advanced age (>60 years)
Nulliparity and infertility
Family history of gynecological cancers
Personal history of breast cancer
BRCA mutations (limited data on association)
Never use of oral contraceptives
Late menopause (>55 years).
Screening:
No specific screening protocols due to rarity
Standard gynecological surveillance for high-risk women
CA-125 monitoring (typically markedly elevated)
Transvaginal ultrasound and pelvic examination
High index of suspicion for rapidly growing masses
Genetic counseling based on family history.
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Gross Description
Appearance:
Solid, firm tumor with irregular surface projections
Gray-white to tan cut surface
Papillary excrescences visible grossly
Areas of necrosis and hemorrhage common
Friable, easily bleeding surface
Infiltrative margins
Calcifications may be present (psammoma bodies).
Characteristics:
Complex papillary architecture evident grossly
Heterogeneous appearance with solid and necrotic areas
Pink-tan to gray coloration
Firm to soft consistency depending on necrosis
Prominent surface papillations
Hemorrhagic areas throughout
Calcified areas (gritty texture).
Size Location:
Size ranges from 4-15 cm (often large at presentation)
May involve entire fallopian tube
Fimbrial end commonly involved (70-80% of cases)
Extension to ovarian surface frequent
Bilateral tubal involvement in 20-30%
Peritoneal implants present at diagnosis
Retroperitoneal extension common.
Multifocality:
Multifocal within tube commonly
Skip lesions may be present
Bilateral involvement more common than other variants
Extensive peritoneal seeding
Lymphatic metastases to para-aortic nodes
Hematogenous spread to liver, lung
Advanced stage at presentation typical.
Microscopic Description
Histological Features:
Micropapillary architecture with small papillary tufts lacking fibrovascular cores
High-grade nuclear atypia with enlarged, pleomorphic nuclei
Prominent nucleoli and irregular nuclear membranes
High mitotic activity (>15 mitoses per 10 HPF)
Minimal stromal component
Psammoma bodies may be present
Extensive necrosis common.
Cellular Characteristics:
Pleomorphic epithelial cells with high nuclear grade
Enlarged nuclei with coarse chromatin
Prominent, often multiple nucleoli
Irregular nuclear contours
Moderate to abundant eosinophilic cytoplasm
Loss of cellular polarity
Frequent mitotic figures including atypical forms.
Architectural Patterns:
Micropapillary pattern predominates (>50% of tumor)
Small papillary tufts without fibrovascular cores
Floating clusters in cystic spaces
Solid sheets in some areas
Conventional papillary areas may be present
Cribriform pattern focally
Single cell infiltration at periphery.
Grading Criteria:
High-grade carcinoma (Grade 3) in majority
Architectural grade 3 (solid and micropapillary)
Nuclear grade 3 (marked pleomorphism)
High mitotic count (>15 per 10 HPF)
Extensive necrosis present
Overall assessment typically Grade 3.
Immunohistochemistry
Positive Markers:
CK7 (diffusely positive in epithelial cells)
PAX8 (nuclear, positive in 95% confirming müllerian origin)
CA125 (strongly positive in cytoplasm and luminal surface)
WT1 (nuclear, positive in 80-90%)
p53 (aberrant pattern in majority)
p16 (block-positive pattern)
EMA (epithelial membrane antigen).
Negative Markers:
CK20 (negative, excludes gastrointestinal origin)
CDX2 (negative, excludes intestinal differentiation)
TTF-1 (negative, excludes lung origin)
ER/PR (typically negative or weakly positive)
p63 (negative in tumor cells)
Calretinin (negative, excludes mesothelioma)
Inhibin (negative).
Diagnostic Utility:
PAX8 positivity confirms müllerian/gynecological origin
WT1 positivity supports serous-like differentiation
p53 aberrant pattern characteristic of high-grade carcinoma
p16 block positivity supports high-grade diagnosis
CK7+/CK20- pattern consistent with gynecological primary
Negative ER/PR typical of high-grade serous-like tumors.
Molecular Subtypes:
p53 aberrant subtype (overexpression or null pattern)
High proliferation subtype (very high Ki-67)
Serous-like subtype (WT1 positive, ER/PR negative)
Chromosomally unstable subtype
Homologous recombination deficient subtype (subset)
Immune-excluded subtype (low immune infiltrate).
Molecular/Genetic
Genetic Mutations:
TP53 mutations (present in 85-95% of cases)
BRCA1/2 mutations (may be present, limited data)
PIK3CA mutations (less common, 10-15%)
RB1 pathway alterations
CCNE1 amplification (cyclin E overexpression)
MYC amplification
Homologous recombination pathway genes (various alterations).
Molecular Markers:
p53 protein accumulation (correlates with TP53 mutations)
Ki-67 proliferation index (very high, >60%)
Chromosomal instability (widespread copy number alterations)
Cyclin E overexpression
PD-L1 expression (variable, often low)
Homologous recombination deficiency score (may be elevated)
Microsatellite stability (majority).
Prognostic Significance:
Very poor prognosis (worse than conventional high-grade serous)
Advanced stage at diagnosis (majority Stage III-IV)
Rapid disease progression
High metastatic potential
Poor response to chemotherapy
Short overall survival (median 10-15 months)
Early recurrence after treatment.
Therapeutic Targets:
Platinum-based chemotherapy (carboplatin plus paclitaxel)
PARP inhibitors (for HR-deficient cases)
Anti-angiogenic agents (bevacizumab)
Immunotherapy (limited efficacy due to low TMB)
Cell cycle inhibitors (targeting p53/RB pathways)
Aurora kinase inhibitors
Clinical trials for novel agents.
Differential Diagnosis
Similar Entities:
High-grade serous carcinoma with micropapillary features
Conventional papillary serous carcinoma
Cribriform carcinoma (has true luminal spaces)
Solid carcinoma with pseudomicropapillary pattern
Metastatic micropapillary carcinoma from lung or breast
Poorly differentiated adenocarcinoma
Transitional cell carcinoma.
Distinguishing Features:
Micropapillary vs conventional papillary: Absence of fibrovascular cores vs presence
Micropapillary vs cribriform: Tufting pattern vs sieve-like spaces
Primary vs metastatic: PAX8 positivity, clinical history, imaging
True micropapillary vs pseudomicropapillary: Architecture and growth pattern.
Diagnostic Challenges:
Distinguishing from high-grade serous carcinoma
Recognizing micropapillary pattern in limited tissue
Differentiating from metastatic disease
Mixed histological patterns
Crush artifact in small biopsies
Sampling issues due to extensive necrosis.
Rare Variants:
Mixed micropapillary and serous pattern
Micropapillary with solid areas
Micropapillary with cribriform features
Pleomorphic micropapillary variant
Micropapillary with clear cell areas
Micropapillary with neuroendocrine features
Invasive micropapillary with DCIS-like areas.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
[Unilateral/Bilateral] salpingo-oophorectomy with hysterectomy, fallopian tube measuring [size] cm with papillary tumor
Diagnosis
Micropapillary carcinoma of fallopian tube
Classification
High-grade adenocarcinoma with micropapillary pattern (Grade 3)
Histological Features
Shows micropapillary architecture with small papillary tufts lacking fibrovascular cores and high-grade nuclear atypia
Micropapillary Pattern
Micropapillary architecture present in >50% of tumor, papillary tufts without fibrovascular cores, floating clusters
Histological Grading
Grade 3: Micropapillary/solid architecture, marked nuclear pleomorphism, high mitotic count (>15/10 HPF)
Extent of Disease
Size: [X] cm, Pattern: [micropapillary/infiltrative], Necrosis: [extensive], LVI: [present]
Special Studies
PAX8: positive, WT1: positive (serous-like differentiation), CK7: positive
p53: [aberrant pattern], p16: block-positive pattern
Ki-67 index: [very high, >60%]
Molecular Features
p53 aberrant pattern consistent with TP53 mutation, Consider BRCA testing and HRD assessment
FIGO Staging
FIGO Stage: [II/III/IV] - [advanced stage at presentation]
Prognostic Factors
Micropapillary carcinoma (very poor prognosis), High-grade (Grade 3), Advanced stage, Extensive LVI
Final Diagnosis
Primary fallopian tube micropapillary carcinoma, FIGO Stage [II/III/IV]