Mucinous carcinoma of breast: Cytodiagnosis of a case.

Mucinous carcinoma of the breast is a relatively rare, pure form accounting for 2% of all breast cancers. Pure mucinous carcinoma of the breast has a favorable prognosis. The common age is postmenopausal group. Here, we report a 30-year-old female patient diagnosed on cytology as mucinous carcinoma of the breast with lymph node metastasis and subsequently confirmed by histopathology. In 1 year follow-up, the patient did not show pulmonary or distant metastasis and received adjuvant chemotherapy at every 3 weeks interval.

Introduction

Mucinous carcinoma of the breast is uncommon, the reported incidence of pure mucinous carcinoma being 2% of all breast cancers.[12] Traditionally, pure and mixed variants of mucinous carcinoma have been described.[23] Pure mucinous carcinoma has a far better prognosis than the mixed variety noted in several studies.[23] We report a case diagnosed as pure mucinous carcinoma breast on fine needle aspiration cytology (FNAC) in a female of reproductive age group.

Case Report

A 30-year-old female presented with a large firm lump in upper quadrant of right breast for 4 years, which was gradually increasing in size and was associated with pain. The mass measured 10×10 cm and was fixed to the underlying structures. The overlying skin was normal and nipple was not retracted. No axillary lymph node was palpable. The clinical diagnosis of carcinoma right breast was made. FNAC of mass was advised.

Pathological findings

Fine needle aspiration was done from right breast mass. Smears showed abundant pink mucoid material. There were numerous moderately pleomorphic epithelial cells lying either discretely forming loose clusters or entrapped within stromal material [Figure 1]. At places, the cells were forming tubular structures. Mitotic figures were also seen. The cytological findings were suggestive of mucus secreting carcinoma. The patient underwent a radical mastectomy with axillary lymph node clearance.

Figure 1

FNAC smear showing abundant pink mucoid material (arrow) with entrapped tumor cells (arrow head) (H and E, ×400)

Right mastectomy specimen with axillary tail measuring 20 cmΧ14 cmΧ4 cm was received. Overlying skin measured 20 cmΧ11 cm, and the axillary tail measured 9 cm×6 cm×2 cm. Cut surface revealed circumscribed mass with variegated appearance, grey brown in color, and solid to cystic with areas of necrosis and hemorrhage. Tumor mass measured 7 cm×6 cm×5 cm, and extended from subepidermal tissue to posterior resected margin.

Four lymph nodes were identified in axillary tail, with the largest measuring 3 cm×2 cm×1 cm and the smallest measuring 1 cm×0.5 cm×0.5 cm. Cut surface of the largest was gelatinous and necrotic. Three axillary lymph nodes with fibrofatty tissue received separately ranged from 0.5 to 1.5 cm, and had unremarkable cut surface.

Sections from different areas of specimen were studied. Sections from tumor mass revealed large areas of necrosis, myxoid degeneration and lakes of mucoid material [Figure 2]. The tumor cells were round to polyhedral, exhibiting mild pleomorphism but frequent mitotic figures. These cells were mostly arranged in thin trabeculae, single rows and few solid cellular areas. Stroma was delicate in the form of fibrous bands. At places, tubular and cribriform patterns were present. Adjacent breast tissue showed suppurative inflammatory reaction. Tumor was reaching close to posterior resected margin but was separated by a thin rim of uninvolved fibroadipose tissue. All other resected margins were free. Microscopically, seven lymph nodes were identified of which the largest was almost completely replaced by tumor metastasis. Other lymph nodes showed non-specific reactive lymphoid and sinusoidal hyperplasia. Histopathological diagnosis of mucinous carcinoma (cellular variant) was given. Tumor tissue was negative for estrogen receptor (ER) and progesterone receptor (PR).

Figure 2

Section showing lakes of mucoid material (arrow) with enmeshed column of tumor cells (arrow head) (H and E, ×400)

Discussion

Mucinous carcinoma of the breast is an uncommon entity seen in postmenopausal females, accounting for only 2% of all breast carcinomas.[12] However, we are reporting a case of mucinous carcinoma in a young female aged 30 years. The behavior of the tumor tends to be less aggressive, so it has a better prognosis than other breast malignancies. The pure mucinous carcinomas are further subdivided into cellular and hypocellular variants. As soon as another pattern becomes evident as a component of tumor mass, the lesion qualifies as a mixed tumor. The most common admixture is with regular invasive duct carcinoma. Our case was the cellular variant of pure mucinous carcinoma breast.

Two lesions most likely to be confused with mucinous carcinoma are mucoid fibroadenoma and mucocele like lesion.[4] Mucinous carcinoma is ER positive, and in less than 70% cases, it is PR positive.[56] However, in our case, it was both ER and PR negative. Nearly all pure mucinous carcinomas are diploid, while over 50% of mixed variety is aneuploid. Only 3–15% of pure variety shows axillary node metastasis compared to 33–46% of the mixed type.[37] In the present case, one axillary node was positive for tumor deposits. Late distant metastases may occur.[28] The present case did not show any distant metastasis either at the time of diagnosis or during the 1 year of follow-up. Adjuvant chemotherapy containing cyclophosphamide, adriamycin and 5 fluorouracil (5 FU) was given at every 3 weeks interval. Histochemically, the mucins secreted by this tumor are distinct O-acylated forms of sialomucin.[9] Immunohistochemically, there is strong MUC (mucin) 2 cytoplasmic immunoreactivity and decreased MUC I immunoreactivity compared with ductal carcinoma not otherwise specified (NOS). One-fourth to nearly one-half shows features consistent with endocrine differentiation.[10]

Conclusion

We have reported a case of pure mucinous carcinoma in a young female emphasizing the role of FNAC in its early diagnosis.