Mucocele-like Lesion of the Breast

Definition

• A microscopic mucinous cystic lesion of the breast, at least partially lined by bland epithelium, in which mucin is free in the stroma

Alternate / Historical Names

• Mucocele-like tumor

Diagnostic Criteria

• Pools of mucin in stroma variably lined by bland epithelium
  • May be lined by ordinary or hyperplastic ductal epithelium
    • Designate simply as mucocele-like lesion
  • If lined by atypical epithelium, designate according to degree of atypia:
    • Atypical hyperplasia with mucocele-like lesion
    • DCIS with mucocele-like lesion
• If groups of cells are floating in mucin they must not have complex architecture
• If present, they are individual cells or strips of cells
• Almost always a microscopic lesion

Richard L Kempson MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting:: May 1, 2006

Supplemental studies

Immunohistology

• Not reported

Differential Diagnosis

A number of low grade or benign lesions are characterized by pools of mucin

Mucinous DCIS	Extracellular, intralumenal mucin in a duct lined by DCIS, no mucin in contact with stroma
DCIS with mucocele-like lesion	Typical DCIS with discrete areas of rupture resulting in mucin pools in stroma, no groups of cells floating in mucin
ADH with mucocele-like lesion	Some but not all features required for diagnosis of DCIS with discrete areas of rupture resulting in mucin pools in stroma, no groups of cells floating in mucin
Mucocele-like lesion	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
Mucinous carcinoma	Mucin in contact with stroma, neoplastic cells floating in mucin
Nodular mucinosis	Nodules of stromal mucin, no epithelial component, subareolar

Clinical

• Nearly always a microscopic lesion
• Clinical significance is determined by the nature of the lining cells

Grading

Grading

• Usually low grade cytology but all degrees of atypia may be found
• If lining is atypical, designate as one of the following:
  • ADH with mucocele-like lesion
  • DCIS with mucocele-like lesion

Staging

• Not applicable

Lists

Mucin Rich Lesions of the Breast

• ADH with mucocele-like lesion
• DCIS with mucocele-like lesion
• Mucinous carcinoma
• Mucinous DCIS
• Mucocele-like lesion
• Nodular mucinosis

Bibliography

• Rosen PP. Mucocele-like tumors of the breast. Am J Surg Pathol. 1986 Jul;10(7):464-9.
• Hamele-Bena D, Cranor ML, Rosen PP. Mammary mucocele-like lesions. Benign and malignant. Am J Surg Pathol. 1996 Sep;20(9):1081-5.
• Michal M, Ludvikova M, Zamecnik M. Nodular mucinosis of the breast: report of three cases. Pathol Int. 1998 Jul;48(7):542-4.
• 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.