Mucinous carcinoma of the breast is not a common disease and its incidence has been reported to range from 1–6% of all primary breast cancers. [1] [2] [3] [4] It is characterized by a large amount of mucin production and in general, defined as having a mucinous component of 50% or more. [5] [6] Histologically, it is classified into two subgroups— pure type and mixed type. [7] [8]

The pure type is the classical type composed entirely of mucinous carcinoma and can be further subdivided into cellular and hypo-cellular variants based on the degree of cellularity. When the mucinous component is mixed with another tumor type, this is the condition of mixed mucinous cancer which is most commonly ductal type (mucinous-ductal).

Immunohistochemistry is not generally required for the confirmation of mucinous breast carcinoma. However, a notable proportion of lesions especially the cellular variant of pure mucinous carcinoma demonstrate neuroendocrine differentiation. These tumors are immunoreactive for chromogranin and synaptophysin. [5] [9] Typically, mucinous carcinoma is estrogen receptor positive.

A 53-year-old female was presented to the breast clinic with a palpable breast lump. Clinically, the lump was suspicious of breast cancer. Mammogram and ultrasound scan also confirmed the suspicious nature of the lump. A free hand needle core biopsy was carried out in the one-stop triple assessment clinic on index presentation. The core biopsy material retrieved had a distinctive gross appearance, with soft, gelatinous consistency and a glistening clear almost see-through surface. (Figure 1) On this typical macroscopic appearance, a diagnosis of ‘mucinous breast carcinoma’ was made, which was subsequently confirmed on microscopic histological examination. The hallmark of mucinous carcinoma is extracellular mucin production, the extent of which varies from tumor to tumor. Typically, mucinous cancer cells in small clusters, sheets, or papillary configurations are dispersed within pools of extracellular mucin. (Figure 2)

Mucinous carcinoma of the breast usually occurs in postmenopausal women. Median age of diagnosis is 71 years (range 25–85 years). [4] [6] It shows more favorable clinicopathological characteristics, such as lower incidence of nodal metastasis, higher expression of estrogen and progesterone receptors and differentiated grade. [2] [6] [10] [11]

The typical gross appearance of the mucinous breast carcinoma is a well-defined cystic mass, consisting of abundant transparent to bloodstained mucin as well as whitish solid parts. [12] This gelatinous and glistening gross appearance of mucinous breast carcinoma on needle core biopsy is similar to the appearance of wallpaper paste used to stick the wallpaper to a wall. We describe it as ‘wallpaper paste sign’ of mucinous breast carcinoma on needle core biopsy because of this similarity in appearances. This sign has been successfully reproducible in our practice over a period of time. Whenever such needle core biopsy appearance is retrieved in the clinic, we write ‘positive wallpaper paste sign– mucinous breast carcinoma?’ on the histology request form. This has always been confirmed on the microscopic analysis and immunohistochemistry when required.

Mucinous breast carcinoma is associated with a relatively favorable prognosis with a 5-year breast cancer specific survival rate of 94%. Although slowly decreasing with time, 10, 15 and 20 years survival rates are 89%, 85% and 81%, respectively compared to 82% (5 year), 72% (10 year), 66% (15 year) and 62% (20 year) for invasive ductal carcinoma. [1] [6] [13] [14] [15]

Mucinous carcinoma is relatively rare type of breast cancer and it can be diagnosed on patient’s first visit to the breast clinic on gross inspection of the needle core biopsy specimen.

1. Louwman MW, Vriezen M, van Beek MW, et al. Uncommon breast tumors in perspective: incidence, treatment and survival in the Netherlands. Int J Cancer 2007;121(1):127–35.   [CrossRef]   [Pubmed]    
2. Andre S, Cunha F, Bernardo M, Meneses e Sousa J, Cortez F, Soares J. Mucinous carcinoma of the breast: a pathologic study of 82 cases. J Surg Oncol 1995;58(3):162–7.   [CrossRef]   [Pubmed]    
3. Li CI, Uribe DJ, Daling JR. Clinical characteristics of different histologic types of breast cancer. Br J Cancer 2005;93(9):1046–52.   [CrossRef]   [Pubmed]    
4. Diab SG, Clark GM, Osborne CK, Libby A, Allred DC, Elledge RM. Tumor characteristics and clinical outcome of tubular and mucinous breast carcinomas. J Clin Oncol 1999;17(5):1442–8.   [Pubmed]    
5. Tan PH, Tse GM, Bay BH. Mucinous breast lesions: diagnostic challenges. J Clin Pathol 2008;61(1):11–9.   [Pubmed]    
6. Di Saverio S, Gutierrez J, Avisar E. A retrospective review with long term follow up of 11,400 cases of pure mucinous breast carcinoma. Breast Cancer Res Treat 2008;111(3):541–7.   [CrossRef]   [Pubmed]    
7. Silverberg SG, Kay S, Chitale AR, Levitt SH. Colloid carcinoma of the breast. Am J Clin Pathol 1971;55(3):355–63.   [Pubmed]    
8. Dogan E, Aksoy S, Dizdar O, et al. Pure mucinous carcinoma of the breast: a single center experience. J Buon 2011;16(3):565–7.   [Pubmed]    
9. Capella C, Eusebi V, Mann B, Azzopardi JG. Endocrine differentiation in mucoid carcinoma of the breast. Histopathology 1980;4(6):613–30.   [CrossRef]   [Pubmed]    
10. Komenaka IK, El-Tamer MB, Troxel A, et al. Pure mucinous carcinoma of the breast. Am J Surg 2004;187(4):528–32.   [CrossRef]   [Pubmed]    
11. Barkley CR, Ligibel JA, Wong JS, Lipsitz S, Smith BL, Golshan M. Mucinous breast carcinoma: a large contemporary series. Am J Surg 2008;196(4):549–51.   [CrossRef]   [Pubmed]    
12. Chen WY, Chen CS, Chen HC, Hung YJ, Chu JS. Mucinous cystadenocarcinoma of the breast coexisting with infiltrating ductal carcinoma. Pathol Int 2004;54(10):781–6.   [CrossRef]   [Pubmed]    
13. Page DL. Special types of invasive breast cancer, with clinical implications. Am J Surg Pathol 2003;27(6):832–5.   [CrossRef]   [Pubmed]    
14. Park S, Koo J, Kim JH, Yang WI, Park BW, Lee KS. Clinicopathological characteristics of mucinous carcinoma of the breast in Korea: comparison with invasive ductal carcinoma-not otherwise specified. J Korean Med Sci 2010;25(3):361–8.   [CrossRef]   [Pubmed]    
15. Hanagiri T, Ono K, Baba T, et al. Clinicopathologic characteristics of mucinous carcinoma of the breast. Int Surg 2010;95(2):126–9.   [Pubmed]