Definition/General
Introduction:
Tubular carcinoma is a well-differentiated subtype of invasive ductal carcinoma of the breast
It is characterized by the presence of well-formed tubules composed of a single layer of epithelial cells
It accounts for approximately 1-2% of all invasive breast cancers and typically has an excellent prognosis.
Origin:
Originates from the terminal duct-lobular unit (TDLU)
The neoplastic cells form well-defined tubules that infiltrate the stroma
The tubules are typically small, round to oval, and have open lumina
The surrounding stroma is often desmoplastic.
Classification:
Classified as a subtype of invasive ductal carcinoma
To be classified as pure tubular carcinoma, at least 90% of the tumor must exhibit a tubular pattern
It is almost always Grade 1 in the Nottingham grading system due to its high degree of differentiation.
Epidemiology:
Typically affects older women, with a mean age of diagnosis in the early 60s
It is rare in women under 40
It is often detected on screening mammography as a small, spiculated mass
The incidence has been stable over the past few decades.
Clinical Features
Presentation:
Often presents as a small, palpable mass
May be detected as a spiculated density on mammography
Nipple discharge is rare
Skin changes are uncommon due to the small size at diagnosis.
Symptoms:
Usually asymptomatic and found on screening
If palpable, it is typically a small, firm, non-tender mass
Pain is uncommon
Axillary lymphadenopathy is rare at presentation.
Risk Factors:
Risk factors are similar to other types of breast cancer, including age, family history, and hormonal factors
No specific risk factors unique to tubular carcinoma have been identified.
Screening:
Mammography is the primary screening tool
Tubular carcinomas often appear as small, irregular, spiculated masses with or without calcifications
Ultrasound can also be used for evaluation.
Master Tubular Carcinoma Pathology with RxDx
Access 100+ pathology videos and expert guidance with the RxDx app
Gross Description
Appearance:
Typically a small, firm, irregular mass
The cut surface is gray-white and gritty
The margins are often ill-defined and spiculated
Necrosis and hemorrhage are rare.
Characteristics:
The tumor is usually less than 2 cm in diameter
The consistency is firm to hard
The cut surface has a characteristic gritty or "crunchy" texture due to the desmoplastic stroma.
Size Location:
Average size is around 1 cm
Most commonly located in the upper outer quadrant of the breast
Multifocality and multicentricity are uncommon.
Multifocality:
Pure tubular carcinomas are usually unifocal
When associated with other types of carcinoma, multifocality may be present
Contralateral breast cancer is rare.
Microscopic Description
Histological Features:
Characterized by well-formed, haphazardly arranged tubules infiltrating a desmoplastic stroma
The tubules are composed of a single layer of uniform epithelial cells
Myoepithelial cells are absent, which is a key feature of invasion.
Cellular Characteristics:
The cells are small, uniform, and cuboidal with scant eosinophilic cytoplasm
Nuclei are small, round, and regular with inconspicuous nucleoli
Mitotic activity is low
Apical snouts may be seen.
Architectural Patterns:
The predominant pattern is well-formed tubules
The tubules are often angulated or tear-drop shaped
A cribriform pattern of DCIS is often associated with tubular carcinoma.
Grading Criteria:
Almost always Grade 1 according to the Nottingham grading system
Tubule formation is high (Score 1)
Nuclear pleomorphism is low (Score 1)
Mitotic count is low (Score 1).
Immunohistochemistry
Positive Markers:
Strongly positive for Estrogen Receptor (ER) and Progesterone Receptor (PR)
Negative for HER2
E-cadherin is positive, confirming its ductal origin
Cytokeratin 7 (CK7) is also positive.
Negative Markers:
HER2 is negative
Myoepithelial markers (p63, calponin, SMA) are negative around the invasive tubules, confirming invasion
Basal cytokeratins (CK5/6, CK14) are negative.
Diagnostic Utility:
IHC is crucial for confirming the diagnosis and ruling out mimics
Absence of myoepithelial markers confirms invasion
ER, PR, and HER2 status are essential for guiding therapy.
Molecular Subtypes:
Almost exclusively of the Luminal A molecular subtype (ER+, PR+, HER2-, low Ki-67), which is associated with a good prognosis.
Molecular/Genetic
Genetic Mutations:
Low frequency of TP53 mutations
PIK3CA mutations are relatively common
Loss of heterozygosity at 16q is a frequent finding
Overall, it has a low genomic instability.
Molecular Markers:
Low Ki-67 proliferation index
Low expression of proliferation-associated genes
High expression of luminal-related genes.
Prognostic Significance:
Excellent prognosis with a 10-year survival rate of over 95%
Lymph node metastasis is rare, occurring in about 10-15% of cases
Distant metastasis is very uncommon.
Therapeutic Targets:
Due to high ER/PR positivity, endocrine therapy (e.g., tamoxifen, aromatase inhibitors) is the mainstay of adjuvant treatment
Chemotherapy is rarely indicated.
Differential Diagnosis
Similar Entities:
Sclerosing adenosis (benign, retains myoepithelial layer)
Microglandular adenosis (benign, lacks myoepithelial layer but is S100 positive)
Radial scar/complex sclerosing lesion (benign, entrapped glands retain myoepithelial cells)
Other well-differentiated invasive carcinomas.
Distinguishing Features:
Sclerosing adenosis has a lobulocentric architecture and a myoepithelial layer
Microglandular adenosis is S100 positive and ER/PR negative
Radial scars have a central fibroelastotic core and entrapped glands with myoepithelial cells.
Diagnostic Challenges:
Distinguishing from benign sclerosing lesions can be challenging on core biopsy
The key is to demonstrate the absence of a myoepithelial layer around the tubules in the suspected invasive component.
Rare Variants:
Pure tubular carcinoma is the main entity
Mixed tubular carcinomas have a component of other types of invasive ductal carcinoma, which may affect prognosis.
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
[diagnosis name]
Classification
Classification: [classification system] [grade/type]
Histological Features
Shows [architectural pattern] with [nuclear features] and [mitotic activity]
Size and Extent
Size: [X] cm, extent: [local/regional/metastatic]
Margins
Margins are [involved/uninvolved] with closest margin [X] mm
Lymphovascular Invasion
Lymphovascular invasion: [present/absent]
Lymph Node Status
Lymph nodes: [X] positive out of [X] examined
Special Studies
IHC: [marker]: [result]
Molecular: [test]: [result]
[other study]: [result]
Final Diagnosis
Final diagnosis: [complete diagnosis]