Mucinous lesions of breast

1. Mucinous lesions of breast
Dr. Seena Tresa Samuel
Pathologist

2. Mucinous carcinoma
• IBC characterized by clusters of epithelial tumor cells
suspended in pools of extracellular mucin
• Colloid carcinoma/mucinoid carcinoma/gelatinous carcinoma
• 2% of all breast carcinoma
• Usually occurs in elderly women (Median age : 71 yr)
• Low level of genetic instability
• Microsatellite instability is rare

3. • Pure mucinous carcinoma (PMC) : >90% mucinous
component
• Low or intermediate- nuclear grade & a low mitotic rate
• Regional lymph node involvement and distant metastases are
unusual findings
• Mixed mucinous carcinoma : 10–90% of mucinous component
• A mucinous component of <10% should be mentioned

4. Gross examination: Glistening and gelatinous nodule with
pushing margin
Size :<1cm to > 20 cm

5. Type A : Hypocellular subtype with clusters of tumor cells in
pools of abundant extracellular mucin. The mucin pools are
partially separated by delicate fibrous septa.

6. Type B : HyperCellular subtype with neuroendocrine differentiation.

7. No prognostic difference between Type A and Type B
mucinous carcinoma

8. Mucinous carcinoma with a cribriform growth pattern
associated with DCIS

9. Luminal A Subtype (ER & PR +, HER2 negative , Low Ki67)
ER PR
HER 2

10. • Low recurrence rate ( Local and distant)
• Rare involvement of axillary lymph nodes
• Associated with good prognosis.

11. • Pure MCs can have micropapillary pattern :
Morula-like clusters suspended in tight mucin pools -
• Mucinous carcinoma with micropapillary features
Intermediate to high grade nuclei
Frequent Hob nail cells
Psammomatous calcification
EMA :Reverse polarity
• MPMC tends to occur at a younger age
• More aggressive tumor behavior (frequent lymph node
metastasis and LVI)

12. Arrangement of tumor cells in a pattern resembling invasive
micropapillary carcinoma
Inset: Psammomatous calcification.

13. Mucinous micropapillary carcinoma with hobnail” cell
morphology showing an inside-out EMA immunostaining
pattern.

14. More than half of mucinous carcinoma with micropapillary
pattern demonstrated lymphovascular invasion

16. Acellular mucin in the primary tumor bed (A) and lymph node
(B) is considered a pathologic complete response following
neoadjuvant chemotherapy

17. MUCOCELE LIKE LESIONS
• MLLs consist of ruptured mucinous cysts and extravasated
mucin.
• The cysts lined by flat-to-columnar epithelium
• Can be involved by usual ductal hyperplasia ,ADH, and in situ
or invasive carcinoma.
• Large, granular calcifications are often present within the
mucin.

18. mucin-containing dilated ducts that ruptured, with resultant
extravasation of mucin into surrounding stroma

19. Characteristic granular calcifications within extravasated mucin

20. Benign MLL in a background of columnar cell change and
hyperplasia, fibrosis, and inflammation

21. ADH adjacent to a ruptured mucinous cyst

22. A focus suspicious for microinvasion associated with a
ruptured mucinous cyst with atypia.

23. Free-floating benign epithelium within extravasated mucin can be
mistaken for mucinous carcinoma. Presence of myoepithelial cells
adherent to detached epithelial strips may be helpful.

24. Pitfalls: Mucocelelike Lesions
• The presence of strips or clusters of epithelium floating
within the mucin of an MLL involved by ADH or DCIS may
raise consideration for mucinous carcinoma.
• Epithelial displacement is favored if
a. The floating epithelium is scant or
b. Associated with myoepithelial cells or
c. contiguous with the cyst lining.

25. Mucinous cystadenocarcinoma
• IBC characterised by cystic structures lined by tall columnar
cells with stratifications, tufting and papillary formation.
• Abundant intracytoplasmic mucin.
• Mucin is also present within cystic spaces
• Resembles pancreatobiliary or ovarian mucinous
cystadenocarcinoma
• DCIS may be present in the adjacent mammary ducts

26. cystic structures lined by tall columnar cells

27. IHC
• Usually ER,PR and HER2 negative
• CK7 positive
• CK20 and CDX2 negative

28. • Usually ER,PR and HER2 negative
• CK7 positive
• CK20 and CDX2 negative

29. Invasive lobular carcinoma with extracellular mucin
production
• Most commonly associated with the classic sub type of ILC
• Mucinous component : single cells, clusters or single file
arrays floating in mucin.
• Non mucinous ILC component was present in all cases.
• Membranous E-cadherin is absent
• The tumors are ER and PR positive and HER2 negative

30. ILC with extracellular mucin production. Non mucinous classic
ILC component also seen

31. Solid papillary carcinoma
• Expansile nodules with solid growth pattern and delicate
fibrovascular cores.
• Myoepithelial cell layer is absent within the fibrovascular cores
• Frequent neuroendocrine differentiation.
• Primarily in postmenopausal women

32. Intracellular or extracellular mucin may be present

33. Mucoepidermoid carcinoma
• Very rare malignant salivary gland–type tumor
• Microscopy resembles salivary gland counterpart
• Composed of varying proportions of distinctive mucinous,
intermediate and epidermoid cells

34. Nodular mucinosis of breast
• A very rare non neoplastic lesion
• Subareolar region of young women.
• Multinodular myxoid or mucinous lesion with sparse bland
spindle cells and fibrocollagenous stroma.
• No epithelial components can be identified.

35. a. Well circumscribed, but not encapsulated lesion
b. Abundant myxoid tissue with a few scattered spindle cells

36. • The myxoid material is strongly positive on Alcian blue and
Hale colloidal iron special stains.
• A lack of epithelial elements distinguishes nodular
mucinosis from MLLs and mucinous carcinoma

37. Miscellaneous mimic: Silicone leakage from implant in
reconstructed breast
• Foreign body giant cell reaction, inflammatory changes, and
fibrosis usually seen
• Extracellular silicone can be seen as non birefringent crystals

38. THANK YOU