Breast

Other carcinoma subtypes, not WHO classified

Tubulolobular carcinoma



Last staff update: 4 March 2024 (update in progress)

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PubMed Search: Tubulolobular carcinoma

Hafsa Nebbache, M.D.
S. Emily Bachert, M.D.
Page views in 2024 to date: 1,735
Cite this page: Nebbache H, Bachert SE. Tubulolobular carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastmalignanttubulolobular.html. Accessed March 29th, 2024.
Definition / general
Essential features
  • Carcinoma with areas of tubular carcinoma and invasive lobular carcinoma
  • Most are estrogen receptor (ER) positive and HER2 negative
  • Not synonymous with invasive carcinoma with ductal and lobular features
Terminology
  • In the 5th edition of the WHO Classification of Breast Tumours, tubulolobular carcinoma is considered a histologic variant of invasive lobular carcinoma; however, many authors consider this histological pattern a variant of invasive breast carcinoma of NST (Diagnostics (Basel) 2022;12:2658)
ICD coding
  • ICD-11: XH3RK9 - tubulolobular carcinoma
Epidemiology
Sites
Etiology
  • Etiology is multifactorial: genetics, hormones, diet, age and reproductive factors are risk factors (WHO 5th edition)
  • ER positive pathway of breast cancer development characterized by gains of 1q and losses of 16q (WHO 5th edition)
  • See etiologies associated with low grade, ER positive invasive breast cancer of no special type (NST)
  • Expression of E-cadherin supports ductal differentiation, despite a dominant lobular growth pattern (Am J Surg Pathol 2004;28:1587)
Clinical features
Diagnosis
  • Diagnosis can be made on core needle biopsy or resection specimens
Radiology description
Prognostic factors
Case reports
Treatment
  • Localized excision / mastectomy
  • Choice of treatment is based on the size and the tumor stage: localized excision, radical or modified radical mastectomy, hormone therapy and adjuvant therapy (Mod Pathol 2007;20:130)
Gross description
  • Ill defined, firm, gray tumor, usually measuring < 2 cm in greatest dimension, ranging in size from 0.5 cm to 2.5 cm (median, 1.4 cm) (Am J Surg Pathol 2004;28:1587)
Microscopic (histologic) description
  • Invasive tumor with mixed pattern of small tubules with a lobular pattern of infiltration within a dense collagenous stroma often with prominent elastosis
    • Tubular component: small, round to angulated tubules with low grade nuclei and variable apical snouts
    • Lobular component: single cells, single file cords of cells, often displaying targetoid growth around benign ducts
    • Cells are uniform and display low grade nuclear atypia (nuclear grade 1 or 2) with inconspicuous nucleoli and minimal amphophilic cytoplasm
    • Cells with lobular growth pattern may show occasional intracytoplasmic lumina and rare signet ring morphology
  • Can have variable proportion of tubular and lobular components
  • Usually well differentiated (grade 1); can be moderately differentiated
    • Nuclear score can be grade 1 - 2
  • May have associated ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS)
  • Lacks surrounding myoepithelial cell layer
  • References: Mod Pathol 2007;20:130, Am J Surg Pathol 2004;28:1587, Breast Care (Basel) 2008;3:423
Microscopic (histologic) images

Contributed by S. Emily Bachert, M.D. and AFIP
Haphazard arrangement

Haphazard arrangement

Infiltrative pattern

Infiltrative pattern

Tubular and lobular components

Tubular and lobular components

Fibrous stroma

Fibrous stroma


Predominantly lobular component

Predominantly lobular component

Infiltrative tubules

Infiltrative tubules

Single file cells

Single file cells

ER+

ER+

Cytology description
  • Diagnosis can be suggested but not definitively made on cytologic preparations
  • Single filing of cells and tubular structure formation
  • Low nuclear grade
  • Low mitotic rate
  • Intracytoplasmic vacuoles and rare nucleoli (Acta Cytol 1996;40:465)
Positive stains
Negative stains
Sample pathology report
  • Right breast, excision:
    • Tubulolobular carcinoma, well differentiated, measuring 1.5 cm
    • Nottingham grade I / III: tubule score = 1, nuclear score = 1, mitoses score = 1
Differential diagnosis
Board review style question #1

Which of the following is true regarding the histologic subtype of the breast carcinoma shown above?

  1. The tumor will most likely be ER negative and HER2 positive
  2. The tumor will most likely be ER positive and HER2 negative
  3. The tumor will most likely be negative for E-cadherin
  4. The tumor will most likely be positive for SMMHC and p63
Board review style answer #1
B. The tumor will most likely be ER positive and HER2 negative. The picture depicts an invasive carcinoma with small round tubules and single filing of cells, compatible with a tubulolobular carcinoma of the breast. Answer A is incorrect because the vast majority of these tumors are ER positive and HER2 negative. Answer C is incorrect because E-cadherin is usually positive in these tumors as they have tubule formation. Answer D is incorrect because these tumors will be negative for myoepithelial markers, compatible with invasive carcinomas.

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Reference: Tubulolobular carcinoma
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