Definition/General
Introduction:
Vulvar mucinous carcinoma is a rare variant of adenocarcinoma characterized by abundant extracellular mucin production
Comprises less than 1% of all vulvar malignancies
Shows lakes of mucin with floating tumor cells
May arise from Bartholin glands or surface epithelium
Demonstrates variable prognosis depending on grade.
Origin:
Most commonly arises from Bartholin glands
Can originate from minor vestibular glands
May arise from surface epithelium with mucinous metaplasia
Shows goblet cell differentiation
Associated with endometriosis in some cases.
Classification:
Classified as adenocarcinoma, mucinous type
WHO classification includes under glandular tumors
Similar morphology to ovarian mucinous carcinoma
Intestinal-type or endocervical-type differentiation
Graded based on nuclear features.
Epidemiology:
Peak incidence in 5th-6th decades
No clear HPV association
May be associated with endometriosis
Higher incidence in multiparous women
Better prognosis than high-grade adenocarcinomas when well-differentiated.
Clinical Features
Presentation:
Vulvar mass or cystic lesion
May present as mucoid discharge
Bleeding (contact or spontaneous)
Vulvar swelling and discomfort
Slow growth pattern initially
May be mistaken for cyst.
Symptoms:
Mucoid discharge (70-80%)
Vulvar swelling (60-70%)
Bleeding episodes (40-50%)
Vulvar discomfort (40%)
Mass effect symptoms
Often asymptomatic initially.
Risk Factors:
History of endometriosis
Previous ovarian mucinous tumors
Advanced age (>50 years)
Chronic vulvar inflammation
No established HPV association.
Screening:
Regular gynecological examination
Imaging for cystic lesions
Mucin analysis if possible
Comprehensive staging workup
Family history assessment.
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Gross Description
Appearance:
Well-circumscribed cystic mass with gelatinous contents
Mucoid, translucent cut surface
Soft consistency with firm areas
May show multilocular pattern
Abundant mucin on cut surface.
Characteristics:
Size typically 3-12 cm in diameter
Cystic and solid components
Cut surface shows pools of mucin
May have papillary projections
Gelatinous consistency.
Size Location:
Variable size (usually 5-10 cm)
Most commonly Bartholin gland region
May involve vestibular area
Posterior vulva common site
Usually unilateral.
Multifocality:
Usually unifocal
May be associated with endometriotic lesions
Local extension possible
Lymph node involvement depends on grade
Peritoneal spread possible (high-grade cases).
Microscopic Description
Histological Features:
Characterized by abundant extracellular mucin pools
Floating tumor cells in mucin lakes
Glandular architecture
Variable nuclear atypia
Goblet cell differentiation.
Cellular Characteristics:
Columnar cells with basal nuclei
Abundant apical mucin
Variable nuclear pleomorphism
Goblet cells present
Mitotic activity variable
Well to moderately differentiated.
Architectural Patterns:
Mucin pools with floating cells
Glandular pattern
Cribriform areas may be present
Papillary architecture possible
Stromal invasion pattern variable.
Grading Criteria:
Three-tier grading system
Grade based on nuclear atypia
Grade I: Minimal atypia
Grade II: Moderate atypia
Grade III: Marked atypia
Mitotic activity assessment.
Immunohistochemistry
Positive Markers:
CK7 (positive)
CK20 (variable)
CEA (positive)
CDX2 (intestinal-type)
MUC2 (intestinal mucin)
MUC5AC (gastric-type)
PAX8 (variable).
Negative Markers:
p63 (negative)
CK5/6 (negative)
TTF-1 (negative)
ER/PR (usually negative)
WT1 (negative)
Vimentin (negative).
Diagnostic Utility:
CK7/CK20 pattern helps determine mucinous subtype
CDX2 indicates intestinal differentiation
MUC2 confirms intestinal-type mucin
CEA supports adenocarcinoma diagnosis
Mucin stains highlight extracellular mucin.
Molecular Subtypes:
Intestinal-type (CK20+, CDX2+)
Endocervical-type (CK7+, CK20-)
Gastric-type (MUC5AC+)
Different prognostic implications.
Molecular/Genetic
Genetic Mutations:
KRAS mutations (40-60%)
PIK3CA mutations (20-30%)
TP53 mutations (variable)
APC mutations (intestinal-type)
GNAS mutations (some cases).
Molecular Markers:
Low Ki-67 proliferation index (well-differentiated)
Wild-type p53 pattern common
β-catenin expression patterns variable
Mucin gene expression profiles
Microsatellite stability typical.
Prognostic Significance:
Grade-dependent prognosis
Well-differentiated cases have better prognosis
High-grade cases more aggressive
Stage at presentation crucial
Size correlates with outcome.
Therapeutic Targets:
Surgical excision primary treatment
Chemotherapy (advanced/high-grade cases)
Targeted therapy under investigation
Mucin reduction strategies experimental.
Differential Diagnosis
Similar Entities:
Metastatic mucinous adenocarcinoma (ovarian, colorectal)
Mucinous cystadenoma
Bartholin gland cyst
Endometriotic cyst
Pseudomyxoma peritonei.
Distinguishing Features:
Primary vulvar: Clinical presentation
Primary vulvar: No other primary site
Ovarian metastasis: PAX8 positive
Colorectal metastasis: CK20 positive, CDX2 positive
Benign cyst: No atypia
Benign cyst: No invasion.
Diagnostic Challenges:
Differentiation from metastatic disease
Distinction from benign mucinous lesions
Assessment of invasion
Grading assessment
Extensive workup required to exclude metastases.
Rare Variants:
Mixed patterns with other adenocarcinoma types
Signet ring features
Neuroendocrine differentiation
Colloid carcinoma pattern.
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
[specimen type], measuring [size] cm in greatest dimension
Diagnosis
Vulvar Mucinous Carcinoma
Classification
Classification: Adenocarcinoma, mucinous type, Grade [I/II/III]
Histological Features
Shows abundant mucin pools with [floating tumor cells] and [glandular differentiation]
Size and Extent
Size: [X] cm, extent: [local invasion present/absent]
Grade Assessment
Grade: [I/II/III] based on [nuclear atypia] and [architectural complexity]
Margins
Margins are [involved/uninvolved] with closest margin [X] mm
Mucin Assessment
Extracellular mucin comprises [X]% of tumor volume
Immunohistochemistry
CK7: [positive/negative], CK20: [positive/negative]
CDX2: [positive/negative], MUC2: [positive/negative]
CEA: [positive/negative]
Mucinous Subtype
Pattern consistent with [intestinal-type/endocervical-type/gastric-type] differentiation
Prognostic Factors
Tumor size, grade, mucin subtype, invasion pattern
Final Diagnosis
Vulvar Mucinous Carcinoma (Adenocarcinoma, mucinous type, Grade [I/II/III])