Pools of mucin in stroma variably lined by bland epithelium, usually no groups of cells floating in mucin (if present they are normal ductal cells and are not complex), almost always a microscopic lesion
Michal M, Ludvikova M, Zamecnik M. Nodular mucinosis of the breast: report of three cases. Pathol Int. 1998 Jul;48(7):542-4.
Arihiro K, Inai K, Kurihara K, Takeda S, Khatun N, Kuroi K, Kawami H, Toge T. Myxoma of the breast: report of a case with unique histological and immunohistochemical appearances. Acta Pathol Jpn. 1993 Jun;43(6):340-6. (appears to be the same lesion as nodular mucinosis)
Wee A, Tan CE, Raju GC. Nerve sheath myxoma of the breast. A light and electron microscopic, histochemical and immunohistochemical study. Virchows Arch A Pathol Anat Histopathol. 1989;416(2):163-7. (appears to be the same lesion as nodular mucinosis)
Sanati S, Leonard M, Khamapirad T, Eltorky MA. Nodular mucinosis of the breast: a case report with pathologic, ultrasonographic, and clinical findings and review of the literature. Arch Pathol Lab Med. 2005 Mar;129(3):e58-61.