The clinical, mammographic and low grade cytologic features of mucinous carcinoma can make it difficult to diagnose by fine needle aspiration (FNA). Fine needle aspirates of mucinous carcinoma were reviewed with the mammographic findings to improve the diagnostic criteria and specificity for FNA.
All aspirates were reviewed for cytologic criteria and cellularity, atypia and single epithelial cells (SEC). A nuclear grade was assigned to each aspirate. The mammographic findings were correlated with the FNA diagnoses.
Forty-five patients with an aspirate and confirmed diagnosis of mucinous carcinoma were identified. The clinical impressions were: benign tissue (5), fibroadenoma (6) and cancer (32). The initial cytologic diagnoses were: adenocarcinoma (32), atypical/suspicious for cancer (11), insufficient (1) and negative (1). The cytologic findings showed smears with increased cellularity (35/45 cases) and minimal atypia. SEC with eccentrically located nuclei and eosinophilic cytoplasm were numerous. The assigned nuclear grade was as follows: grade 1, 16 cases; grade 2, 20 cases; and grade 3, 6 cases. Abundant mucin was present in Papanicolaou-stained slides in 23 cases; focal mucin was observed in 14 cases. The mammograms showed a smoothly outlined to lobulated mass with only slight irregularities identified.
Mucinous carcinoma has a cytologic pattern that includes increased cellularity, with numerous single cells and abundant mucin. Although the mammographic findings may mimic a benign lesion, in the most patients a specific diagnosis of mucinous carcinoma can be made by FNA.