Micropapillary Variant of Invasive Mucinous Carcinoma - A Case Report and Review of Literature

ABSTRACT


INTRODUCTION
Invasive micropapillary variant of mucinous carcinoma is a special histological subtype of mucinous carcinoma breast.It shows combination of features of both mucinous carcinoma and invasive micropapillary carcinoma breast.Unlike other subtypes of mucinous carcinoma breast, these tumours exhibit frequent nodal metastasis and angioinvasion, which warrants more aggressive treatment.Greater awareness of this variant is required among pathologists and clinicians for a better patient overall survival.

CASE REPORT
We here describe a case of micropapillary variant of invasive mucinous carcinoma breast.A 43year, old female with no significant previous medical history, presented with a palpable lump in her right breast.Physical examination revealed a hard lump with irregular margins in the upper outer quadrant and measured around 3 x 2 cm.Three axillary lymph nodes were palpable, which were fixed and largest measured 1 x 1 cm.Mammography revealed a well-defined irregular lesion with spiculated margin, BIRADS 5, in the superolateral quadrant of right breast with axillary lymph nodes.Then a fine needle aspiration cytology was performed and a diagnosis of carcinoma breast IAC CODE 5 was made.Later trucut biopsy was taken and the histopathological report was suspicious of mucinous carcinoma breast.Following this right modified radical mastectomy was done.On gross examination, identified an ill circumscribed pale grey white lesion with mucinous appearance measuring 4 x 3.5 x 3.5cm, well away from all the margins.On microscopy, a neoplasm composed of cells arranged in micropapillary pattern surrounded by abundant extracellular pools of mucin is seen (Fig. 1), individual cells being moderately pleomorphic with scant to moderate eosinophilic cytoplasm and pleomorphic vesicular nucleus with coarse clumped chromatin (Fig. 2).Also seen occasional hobnailing of cells (Fig. 3) and extensive psammomatous calcification (Fig. 4, Fig. 5).6).On immunohistochemical examination, ER (Fig. 7) and PR (Fig. 8) shows positive expression and Her 2Neu shows negative expression.EMA shows staining in the peripheral border of micropapillary cluster (Fig. 9) and Ecadherin shows staining of central pseudolumina (Fig. 10).
A diagnosis of invasive micropapillary variant of mucinous carcinoma breast was given.

Micropapillary Variant of Invasive Mucinous Carcinoma -A Case Report and Review of Literature DISCUSSION Mucinous
carcinomas of the breast are usually indolent tumours affecting the elderly, with low propensity for angioinvasion and nodal metastasis. 1 These tumours are subclassified into pure mucinous carcinoma which has > 90% mucin component and mixed mucinous carcinoma which has 10-90% mucin component.Generally, pure mucinous carcinoma may be hypocellular variant or hypercellular variant with neuroendocrine differentiation. 2 Apart from these two, there is another rarely recognized variant of pure mucinous carcinoma, known as invasive micropapillary variant of mucinous carcinoma breast.3-5Thisentityhasamicropapillaryarchitecturewitha predilection for nodal metastasis and angioinvasiveness.6Literatureconsiderthis as a hybrid of pure mucinous carcinoma and micropapillary carcinoma.Interestingly its clinical behaviour and morphology are straddled between these two. 5as first described in 2002 by Wai Kuen Ng.7It accounts for <1% of all breast cancers.Invasive micropapillary variant of mucinous carcinoma accounts for < 1% of all breast cancers and 12-35% of all pure mucinous carcinoma.5,8,9Butthe reported cases are far less due to its underrecognition.
9The affected individuals belong to a wide age group, 28-80 years (mean 55years) and half of them are in the pre-or perimenopausal age group. 1 Patients usually present in T1-T4 stage.The common site being upper outer quadrant followed by central quadrant of breast.10

Micropapillary Variant of Invasive Mucinous Carcinoma -A Case Report and Review of Literature
CONCLUSIONIn summary, Invasive micropapillary variant of mucinous carcinoma occupies intermediate portion of a spectrum of breast carcinoma phenotype with pure mucinous carcinoma at one end and invasive micropapillary carcinoma at the other end.Invasive micropapillary variant of mucinous carcinoma, which is now identified as a subtype of pure mucinous carcinoma has a clinical behaviour and propensity for nodal metastasis and angioinvasion intermediate between pure mucinous carcinoma and micropapillary carcinoma.Previous studies emphasises that presence of this micropapillary architecture in pure mucinous carcinoma modifies its biologic behaviour and has to be managed more aggressively than other subtypes of pure mucinous carcinoma.Therefore, awareness of this underrecognized category and its accurate diagnosis is important for patient management.