Aspiration Biopsy of Mammary Lesions With Abundant Extracellular Mucinous Material: Review of 43 Cases With Surgical Follow-up

Abstract

We reviewed 43 fine-needle aspiration biopsy (FNAB) smears with abundant extracellular mucinous material to determine whether accurate classification of mucinous lesions is achievable on FNAB: 26 had carcinoma (pure colloid carcinoma [CCA], 23; mixed CCA/invasive ductal carcinoma [IDC], 3); 17 had benign lesions on follow-up (benign MLL, 6; fibrocystic change [FCC], 6; myxoid fibroadenoma [MFA], 5). All carcinomas were identified correctly as malignant on FNAB. The initial cytologic diagnoses in benign cases were benign in 8, atypical in 8, and "suspicious" for carcinoma in 1. CCAs were moderate to markedly cellular with mild to moderate atypia and lacked oval bare nuclei. Marked nuclear atypia was confined predominantly to cases with mixed CCA/IDC. A distinct feature of CCA was thin-walled capillaries. FCCs and benign MLLs had overlapping cytologic features and showed variable cellularity and no or mild atypia. MFAs were markedly cellular with dyscohesion and variable atypia; stromal fragments and oval bare nuclei were present in every case. Mucinous lesions can be divided into 2 categories by FNAB: those that are adenocarcinomas and those that are not. CCAs have distinctive features that allow a definitive diagnosis on FNAB. Unnecessary surgery can be avoided in MFA by careful evaluation of smear characteristics. Cytologic features of FCC and MLL overlap. Owing to the documented association of MLL with carcinoma, we recommend that lesions that cannot be classified definitively as adenocarcinoma or MFA be considered for conservative excision, even in the absence of atypia.

Performance Characteristics of Mucinous (Colloid) Carcinoma of the Breast in Fine-Needle Aspirates: Observations From the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytopathology

“…[1][2][3][4][5]7 The diagnostic features of MC by breast FNA are well established in the literature. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Mucinous carcinoma often shows grossly visible jellylike mucin when obtained by FNA, which correlates to the abundant mucin in the background of the smears. The mucinous material is much more readily seen on modified Giemsa-stained slides owing to the metachromatic staining of the mucin.…”

“…These include mucinous cysts, benign mucocele-like lesions, mucinous spherulosis, mucocele-like lesion with atypia (atypical ductal hyperplasia), mucocele-like lesion with ductal carcinoma in situ, myxoid changes in fibroadenoma, ductal carcinoma, and lobular carcinomas with mucinous features. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Fine-needle aspiration biopsy has been routinely used for the diagnosis and management of palpable breast lesions. In this setting, false-positive and false-negative rates vary depending on the expertise of the individual performing the biopsy and interpreting the results, as well as the morphologic subtype of breast cancer.…”

“…Distinguishing myxoid fibroadenoma from mucinous carcinoma by FNA biopsy may present a diagnostic challenge. 10,17,26 The myxoid background can be confused with mucin, and the bland cytologic features of the epithelial cells can mimic those seen in MCs. The cell groups in fibroadenomas are much larger and antlerlike than the 3-dimensional cell balls that are usually seen in MCs.…”

“…The smears contain a mixed population of cohesive epithelial and myoepithelial cells, apocrine cells, macrophages, and detached myxoid stromal fragments. [9][10][11][12][13][14][17][18][19][20][21] The myxoid change is often present focally in these benign lesions and not diffusely as seen in MC. The epithelial component of MC has a uniform appearance without myoepithelial cells.…”

Cytomorphology of Common Malignant Tumors of the Breast

“…Fine red granules may be seen in the cytoplasm with Diff-Quik. Another distinctive feature present in many cases of mucinous carcinoma is thin-walled capillaries, either freefloating or coursing through the thick mucin [42][43][44][45].…”