Nodular Mucinosis of the Breast

Definition

• Multinodular accumulation of stromal mucin in the breast

Alternate/Historical Names

• Myxoma of the breast
• Nerve sheath myxoma of the breast

Diagnostic Criteria

• Multiple small myxoid nodules
  • Alcian Blue and Hale colloidal iron positive
  • May contain spindle cells, histiocytes and capillaries
  • Nodules may be collagenized
• Ducts and acini restricted to periphery of nodules
  • May represent sweat glands or breast elements
• Sporadic cases restricted to subareolar location
  • May be elsewhere in breast in patients with Carney syndrome

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

Original posting:: May 1, 2006

Supplemental studies

Immunohistology

Histochemical stains

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

The mucin in all but nodular mucinosis should be strongly positive with the PAS and mucicarmine stains

• Fibroadenomas may show myxoid stromal change
  • They always have an associated epithelial component
  • They are rarely superficial

• Nerve sheath myxoma of the breast (Wee 1989) appears to be the same lesion as nodular mucinosis
  • Use of this term requires a positive S100 stain
• Myxoma of the breast (Arihiro 1993) appears to be the same lesion as nodular mucinosis

Clinical

• Benign
• Involves nipple and subareola in sporadic cases
• If associated with Carney syndrome it may appear in rest of breast

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

Lesions Preferentially Localized to the Nipple and Subareola

• Infiltrating syringomatous adenoma
• Leiomyoma
• Nipple adenoma
• Nodular mucinosis
• Paget disease
• Pleomorphic adenoma

Bibliography

• 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.