Definition/General

Introduction:
-Vulvar apocrine carcinoma is a rare adenocarcinoma subtype arising from apocrine glands with distinctive morphological and immunohistochemical features
-Comprises less than 1% of all vulvar malignancies
-Shows apocrine differentiation with characteristic cytological features
-Similar to apocrine carcinoma of breast
-Demonstrates variable prognosis.
Origin:
-Arises from apocrine glands in vulvar region
-Can originate from modified apocrine glands
-May arise from hidradenoma papilliferum
-Shows apocrine differentiation
-Associated with background apocrine metaplasia.
Classification:
-Classified as adenocarcinoma with apocrine differentiation
-WHO classification includes under glandular tumors
-Shows morphological similarity to breast apocrine carcinoma
-Intermediate to high-grade malignancy
-Requires specific immunohistochemical confirmation.
Epidemiology:
-Peak incidence in 6th-7th decades
-No racial predilection
-No HPV association
-May be associated with hormonal factors
-Better prognosis than conventional adenocarcinomas when well-differentiated.

Clinical Features

Presentation:
-Vulvar nodule or mass
-May present in hair-bearing areas
-Ulceration possible
-Bleeding (contact or spontaneous)
-Slow to moderate growth
-May be associated with discharge.
Symptoms:
-Vulvar mass (90-100%)
-Bleeding episodes (40-50%)
-Serous discharge (30-40%)
-Vulvar discomfort (30%)
-Pruritus (20%)
-Usually painless initially.
Risk Factors:
-Advanced age (>50 years)
-History of apocrine lesions
-Previous hidradenoma papilliferum
-Hormonal factors (unclear)
-No established genetic predisposition.
Screening:
-Regular gynecological examination
-Careful inspection of hair-bearing areas
-Biopsy of persistent nodules
-Dermatological consultation if indicated.

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Gross Description

Appearance:
-Well-circumscribed nodular mass
-Tan to gray-brown cut surface
-Firm consistency
-May show cystic areas
-Solid and cystic components.
Characteristics:
-Size typically 1-6 cm in diameter
-Well to moderately circumscribed
-Cut surface shows solid areas with cysts
-May have hemorrhagic areas
-Brown pigmentation possible.
Size Location:
-Variable size (usually 2-4 cm)
-Hair-bearing areas of vulva
-Labia majora most common
-Mons pubis possible location
-Usually superficial.
Multifocality:
-Usually unifocal
-May be associated with benign apocrine lesions
-Local extension possible
-Lymph node involvement variable
-Metastases possible in high-grade cases.

Microscopic Description

Histological Features:
-Characterized by large cells with eosinophilic cytoplasm
-Apical snouts (apocrine secretion)
-Decapitation secretion
-Variable nuclear atypia
-Glandular architecture.
Cellular Characteristics:
-Large polygonal cells
-Abundant eosinophilic cytoplasm
-Vesicular nuclei
-Prominent nucleoli
-Apical cytoplasmic protrusions
-Variable mitotic activity.
Architectural Patterns:
-Glandular pattern
-Solid areas possible
-Papillary architecture
-Cribriform areas
-Cystic spaces
-Stromal invasion pattern variable.
Grading Criteria:
-Three-tier grading system
-Based on nuclear atypia
-Architectural complexity
-Mitotic activity
-Grade I-II more common
-Grade III indicates poor prognosis.

Immunohistochemistry

Positive Markers:
-GCDFP-15 (gross cystic disease fluid protein)
-Androgen receptor (AR)
-CK7 (positive)
-EMA (positive)
-CEA (positive)
-Mammaglobin (variable)
-GATA3 (positive).
Negative Markers:
-ER (negative)
-PR (negative)
-CK20 (negative)
-TTF-1 (negative)
-CDX2 (negative)
-p63 (negative)
-PAX8 (negative).
Diagnostic Utility:
-GCDFP-15 positivity diagnostic of apocrine differentiation
-AR positivity characteristic
-ER/PR negativity typical
-CK7 positivity supports glandular nature
-Apocrine marker panel confirmatory.
Molecular Subtypes:
-Apocrine-type adenocarcinoma
-AR-positive subtype
-Hormone-independent type
-Similar to breast apocrine carcinoma.

Molecular/Genetic

Genetic Mutations:
-PIK3CA mutations (30-40%)
-TP53 mutations (variable)
-AR pathway alterations
-PTEN loss (some cases)
-Similar profile to breast apocrine carcinoma.
Molecular Markers:
-AR overexpression
-GCDFP-15 expression
-Ki-67 proliferation index (variable)
-p53 expression patterns
-Cyclin D1 expression.
Prognostic Significance:
-Grade-dependent prognosis
-AR status may influence therapy
-Stage at presentation crucial
-Size correlates with outcome
-Well-differentiated cases have better prognosis.
Therapeutic Targets:
-Androgen receptor targeted therapy
-Surgical excision primary treatment
-Anti-androgen therapy experimental
-Chemotherapy (advanced cases).

Differential Diagnosis

Similar Entities:
-Metastatic breast apocrine carcinoma
-Hidradenoma papilliferum (malignant transformation)
-Conventional adenocarcinoma
-Sebaceous carcinoma
-Sweat gland carcinoma.
Distinguishing Features:
-Primary vulvar: Clinical presentation
-Primary vulvar: No breast primary
-Breast metastasis: Clinical history
-Breast metastasis: Bilateral mammography
-Hidradenoma: Benign cytology
-Sebaceous: Sebaceous differentiation
-Sebaceous: Oil Red O positive.
Diagnostic Challenges:
-Differentiation from metastatic breast carcinoma
-Distinction from benign apocrine lesions
-Recognition of apocrine features
-GCDFP-15 and AR staining crucial
-Clinical correlation important.
Rare Variants:
-Mixed patterns with other adenocarcinoma types
-Predominantly solid variant
-Signet ring features (rare)
-Neuroendocrine differentiation (rare).

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 Apocrine Carcinoma

Classification

Classification: Adenocarcinoma with apocrine differentiation, Grade [I/II/III]

Histological Features

Shows apocrine differentiation with [large eosinophilic cells] and [apical snouts]

Size and Extent

Size: [X] cm, extent: [local invasion present/absent]

Grade Assessment

Grade [I/II/III] based on [nuclear atypia], [architecture], and [mitotic activity]

Margins

Margins are [involved/uninvolved] with closest margin [X] mm

Apocrine Differentiation

Apocrine features: [decapitation secretion], [eosinophilic cytoplasm], [apical snouts]

Immunohistochemistry

GCDFP-15: [positive/negative], AR: [positive/negative]

CK7: [positive], EMA: [positive]

ER: [negative], PR: [negative], p63: [negative]

Prognostic Factors

Tumor grade, size, AR status, margin status

Final Diagnosis

Vulvar Apocrine Carcinoma (Adenocarcinoma with apocrine differentiation, Grade [I/II/III])