Definition/General
Introduction:
Fallopian tube adenosquamous carcinoma is a rare malignant tumor containing both adenocarcinomatous and squamous cell carcinomatous components
It represents less than 5% of all fallopian tube carcinomas
It demonstrates mixed histological patterns within the same tumor
It generally has a poor prognosis compared to pure adenocarcinoma.
Origin:
Arises from the tubal epithelium with subsequent squamous differentiation
May develop from endometrioid adenocarcinoma with squamous metaplasia
Metaplastic transformation of müllerian epithelium
Associated with chronic inflammation and hormonal influences
Possible HPV-related pathogenesis in some cases.
Classification:
Classified based on WHO criteria for mixed carcinomas
Collision tumor: two distinct components
Combined tumor: intimate admixture of components
Based on grade: well-differentiated
Moderately differentiated
Poorly differentiated
FIGO staging system applies.
Epidemiology:
Extremely rare tumor with less than 100 reported cases worldwide
Peak incidence in 6th-7th decades
Mean age around 55-65 years
No specific geographic predilection
Associated with nulliparity in some cases
BRCA mutations may increase risk.
Clinical Features
Presentation:
Abdominal or pelvic mass (most common)
Abnormal vaginal bleeding (postmenopausal)
Pelvic pain (dull, aching)
Abdominal distension
Ascites in advanced cases
Bowel symptoms if locally advanced
Constitutional symptoms in metastatic disease.
Symptoms:
Postmenopausal bleeding (60-70% cases)
Lower abdominal pain
Pelvic pressure sensation
Urinary symptoms (frequency, urgency)
Bowel symptoms (constipation, tenesmus)
Weight loss and fatigue
Early satiety.
Risk Factors:
Advanced age (>50 years)
Nulliparity
Family history of ovarian/breast cancer
BRCA1/2 mutations
History of pelvic inflammatory disease
Endometriosis
Hormone replacement therapy
Chronic salpingitis.
Screening:
No specific screening protocols
Pelvic examination for masses
Transvaginal ultrasonography
CA-125 levels (often elevated)
CT/MRI for staging
PET scan for metastatic disease
Genetic counseling for high-risk patients.
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Gross Description
Appearance:
Tumor appears as a solid, friable mass distending the fallopian tube
Gray-white to tan cut surface with areas of necrosis and hemorrhage
Papillary or solid growth pattern
Invasion through tubal wall
May involve both tubes.
Characteristics:
Unilateral involvement more common (60-70%)
Size ranges from 2-15 cm
Friable, hemorrhagic appearance
Necrotic areas frequently present
Solid and cystic components
Extension to ovaries and peritoneum common.
Size Location:
Usually involves ampullary portion of fallopian tube
Average size 5-8 cm at presentation
May extend to fimbrial end
Bilateral involvement in 30-40% cases
Invasion of tubal wall and serosa
Lymph node metastases common.
Microscopic Description
Histological Features:
Adenocarcinomatous component: glandular architecture with malignant epithelial cells
Squamous component: malignant squamous cells with keratinization
Intimate admixture of both components
Invasive growth pattern
Vascular and lymphatic invasion.
Cellular Characteristics:
Adenocarcinomatous cells show pleomorphic nuclei and prominent nucleoli
Squamous cells demonstrate intercellular bridges and keratinization
High mitotic activity
Nuclear pleomorphism in both components
Necrosis and apoptotic bodies frequent.
Architectural Patterns:
Papillary and glandular patterns in adenocarcinomatous areas
Solid nests and keratinizing patterns in squamous areas
Cribriform architecture may be present
Slit-like spaces and comedonecrosis
Invasive fronts with desmoplastic reaction.
Grading Criteria:
Nuclear grade: degree of pleomorphism and chromatin pattern
Mitotic activity: mitoses per high-power field
Architectural differentiation: gland formation in adenocarcinomatous component
Keratinization: degree in squamous component
Overall grade based on highest grade component.
Immunohistochemistry
Positive Markers:
Cytokeratin 7 positive in adenocarcinomatous component
p63 and CK5/6 positive in squamous component
PAX8 positive in glandular areas
WT1 may be positive
p53 often overexpressed
Ki-67 high proliferation index.
Negative Markers:
Cytokeratin 20 usually negative
CDX2 negative (excludes GI origin)
TTF-1 negative (excludes lung origin)
Calretinin negative (excludes mesothelioma)
ER/PR may be negative or focally positive.
Diagnostic Utility:
p63 and CK5/6 confirm squamous differentiation
PAX8 supports müllerian origin
WT1 helps distinguish from other sites
p53 pattern indicates TP53 mutation status
Hormone receptor status guides therapy.
Molecular/Genetic
Genetic Mutations:
TP53 mutations (80-90% cases)
PIK3CA mutations (20-30%)
ARID1A mutations (15-20%)
PTEN mutations (10-15%)
BRCA1/2 mutations in hereditary cases
RB1 mutations in some cases.
Therapeutic Targets:
PARP inhibitors for BRCA-mutant tumors
PI3K/mTOR inhibitors for PIK3CA-mutant cases
Anti-angiogenic agents
Immune checkpoint inhibitors
CDK4/6 inhibitors
Platinum-based chemotherapy.
Differential Diagnosis
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
Fallopian tube specimen with [mass/tumor], measuring [dimensions]
Tumor Location
Tumor located in [ampullary/isthmic/fimbrial] portion of [right/left/bilateral] fallopian tube
Macroscopic Features
Solid, friable tumor measuring [size] with [necrosis/hemorrhage], extending through tubal wall
Microscopic Features
Shows adenosquamous carcinoma with [glandular patterns] and [squamous differentiation with keratinization]
Tumor Grading
Grade: [well/moderately/poorly] differentiated based on [nuclear features and architectural pattern]
Invasion
Shows [depth] invasion with [lymphovascular invasion present/absent]
Immunohistochemistry
CK7: [positive] in glandular component, p63: [positive] in squamous component, PAX8: [result]
Staging
FIGO Stage: [stage] based on [extent of disease]
Final Diagnosis
Adenosquamous carcinoma of fallopian tube, [grade], FIGO Stage [stage]