Figura 5. Membrana circunferencial y proliferaciуn celular. Fue enviada al departamento de radioterapia para tratamiento complementario. Capella y colaboradores dividieron las formas puras en dos grupos principales: A y B.
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Keywords: Breast neoplasm; Mucinous carcinoma; Mammography; Ultrasonography; Magnetic resonance imaging. Abstract: The present essay is aimed at describing the most characteristic imaging findings of mucinous carcinoma of the breast, with emphasis on the patterns related to better prognosis. The authors selected cases of mucinous carcinoma of the breast whose images were available, highlighting the imaging findings suggestive of this subtype of breast cancer, either at mammography, ultrasonography or magnetic resonance imaging.
This tumor shows a wide age distribution, but with higher incidence in elderly 5. Histologically, such variant is characterized by a tumor-like arrangement of neoplastic cells involved by extracellular mucin, in most cases associated with peripheral ductal carcinoma in situ DCIS 6. Cellularity as well as the amount of mucin has large variation among mucinous tumors. The greater the amount of mucin, the better the prognosis is 6. There are two histological presentations with different imaging features and prognoses: pure and mixed types.
The mixed type presents a greater amount of neoplastic cells not involved by mucin, generally in association with a smaller amount of extracellular mucin, which implies intermediate characteristics between the pure type and nonspecific invasive ductal carcinoma NS-IDC , for this reason sometimes referred to as "IDC with mucinous differentiation" 6,7.
The present pictorial essay focus on the most typical imaging findings of such specific type of carcinoma and its subtypes, highlighting findings associated with prognostic prediction. Histological diagnosis The diagnosis of mucinous neoplasm may be suspected at fine-needle aspiration biopsy FNAB , although with low accuracy in the differentiation between benign mucoceles and malignant mucinous lesions MMC.
However, the differentiation between pure and mixed types can only be established after excision and evaluation of the lesion in its whole extent 6,9. Pure type shows indolent growth, while the mixed type presents variable biological behavior, sometimes similar to NS-IDCs Thus, MMCs, specially the pure type, demonstrated a lower histological degree well differentiated tumors , higher hormone receptor HR expression, lower incidence of adverse oncogenes, lower rate of axillary lymph node involvement at diagnosis, and longer disease-free survival with no significant difference in overall survival 7,11, Typically, a MMC presents as an ovoid or round nodule with circumscribed margins.
At mammography, the pure type correlates with circumscribed or micro-lobulated margins, which present a direct relationship with the amount of extracellular mucin 16 , as demonstrated on Figure 1. The mixed type presents more indistinct or spiculated contours secondary to a higher degree of fibrosis and peripheral desmoplasia, similarly to a NS-IDC.
Microcalcifications are not common, and when they occur, rarely represent psammomatous calcifications, most times associated with the presence of peripheral component of DCIS 6,16, Figure 1. A: Female, year-old patient. Craniocaudal view demonstrating nodule with microlobulated margins in the medial quadrant of the right breast, diagnosed as pure MMC.
B: Histological section of the lesion, identifying mucinous tumor with neoplastic cells involved by moderate amount of extracellular mucin. Ultrasonography has higher sensitivity than mammography in the detection of MMCs 16, Figure 2. A: Female, year-old patient with pure MMC, with typical sonographic findings: ovoid and microlobulated nodule, isoechoic to fat tissue and with posterior acoustic enhancement.
B: Female, year-old patient with an ovoid nodule with indistinct and angulated margins, with no noticeable microlobulation, with posterior acoustic enhancement, diagnosed as mixed MMC.
Similarly to morphological findings at mammography and ultrasonography, MMCs, at magnetic resonance imaging, are visualized as ovoid or lobulated masses with predominantly regular contours. The signal intensity is variable on T1-weighted images and with strong signal similar to that of water or vessels on T2-weighted images Figure 3.
Such high signal of the MMCs on T2-weighted images shows direct correlation with the degree of extracellular mucin and has high diagnostic sensitivity, although not pathognomonic, since it is also found in other lesions secondary to necrosis, hemorrhage, edema, myxoid matrix or cystic component In addittion, the presence of intermediate signal on T2-weighted images suggests the mixed type of MMC.
Figure 3. Female, year-old patient with pure MMC. A: Mediolateral, oblique mammographic view demonstrating microlobulated ovoid nodule at the junction of the medial quadrants of the right breast. B: Axial MRI STIR image of the described nodule, demonstrating intense hypersignal onT2-weighted sequence with hypointense septa, common findings in mucinous carcinomas. C: Histological section at microscopy identifying mucinous tumor with a remarkable amount of mucin and little cellularity.
D,E: Dynamic contrast-enhanced, T1-weighted images with fat suppression and subtraction, at the second and fifth minutes, demonstrating predominantly ring-shaped and progressive enhancement, and also marked enhancement of the septa within the lesion.
F: Sagittal 3D reconstruction. On dynamic contrast-enhanced sequences, any enhancement morphology may occur, however, peripheral, ring-shaped or heterogeneous enhancement are more characteristic, and progressive along time Figure 3. The pure type of MMC generally presents mild to moderate enhancement at the early phases, with centripetal tendency determining type 1 progressive curves, a feature demonstrated on Figure 4, or type 2 curve plateau The progressive enhancement pattern is related to the tumor cellularity, nuclear grading, and amount of extracellular mucin.
Thus, an intense enhancement in the first two minutes after gadolinium injection, or a type 3 curve washout must raise suspicion of mixed type MMC or, an even rarer pure tumor with high cellularity Figure 4. Female, year-old patient with anatomopathological diagnosis of pure MMC.
Color mapping of wash-in B and kinetic curve C showing slight enhancement at the early phase with progressive enhancement pattern. As compared with other subtypes of breast cancer, MMCs, in general, present low signal intensity on diffusion-weighted images. High ADC values may be associated with the presence of extracellular mucin and low tumor cellularity.
However, such characteristic seems to be related to a larger extent to pure MMCs, which show high ADC value, similar or greater than benign lesions. Mixed mucinous tumors may exhibit lower ADC values, similarly to other breast cancer subtypes. Figure 5. The imaging findings may suggest both subtypes of MMCs, pure and mixed ones. Radiol Bras. Can MR imaging contribute in characterizing well-circumscribed breast carcinomas?
Rosen PP. Mucinous carcinoma of the breast in comparison with invasive ductal carcinoma: clinicopathologic characteristics and prognosis. J Breast Cancer. Bode MK, Rissanen T. Imaging findings and accuracy of core needle biopsy in mucinous carcinoma of the breast. Acta Radiol. Gobbi H. J Bras Patol Med Lab.
Mucinous carcinoma of the breast: MRI features of pure and mixed forms with histopathologic correlation. Pure and mixed mucinous carcinoma of the breast: pathologic basis for differences in mammographic appearance. Outcome of pure mucinous breast carcinoma compared to infiltrating ductal carcinoma: a population-based study from China. Ann Surg Oncol.
Imaging findings in mucin-containing carcinomas of the breast: correlation with pathologic features. Sonographic appearance of mucinous carcinoma of the breast. Diffusion-weighted imaging of mucinous carcinoma of the breast: evaluation of apparent diffusion coefficient and signal intensity in correlation with histologic findings. Accepted after revision March 7,
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