Breast
Fibrocystic changes
Apocrine metaplasia


Topic Completed: 28 May 2020

Minor changes: 28 May 2020

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PubMed Search: Apocrine metaplasia [title] breast

Carlos C. Diez Freire, M.D.
Shahla Masood, M.D.
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Cite this page: Diez-Freire CC, Masood S. Apocrine metaplasia. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/breastapocrinemetaplasia.html. Accessed October 29th, 2020.
Definition / general
Essential features
  • Cells with abundant eosinophilic cytoplasm and apical snouts
  • Nuclei are round with variable size, vesicular chromatin with prominent nucleoli
  • Supranuclear vacuoles or eosinophilic granules may be present
Epidemiology
Sites
  • Breast parenchyma ducts and lobules
Etiology
Clinical features
  • Grossly palpable cysts can be lined by apocrine epithelium but there are no specific clinical features per se due to the apocrine metaplasia itself
  • Can be concurrent with both benign and malignant lesions (J Clin Pathol 2007;60:1313)
  • Apocrine cysts and hyperplasia with apocrine metaplasia were more common in the breasts of American women in New York than in Japanese women in Tokyo (Hoda: Rosen's Breast Pathology, 4th Edition, 2014)
Diagnosis
  • Histologic examination of tissue removed
Radiology description
  • Mammographic features are nonspecific, although an enlarging lobular or micro lobulated mass may be noted
  • Heterogeneous microcalcification clusters may sometimes represent apocrine metaplasia
  • These findings can lead to needle core biopsy for definitive diagnosis (AJR Am J Roentgenol 2003;180:795)
Prognostic factors
  • No relationship or minimal impact on the development of mammary carcinoma (Hoda: Rosen's Breast Pathology, 4th Edition, 2014)
  • Florida apocrine metaplasia with atypia may coexist with apocrine carcinoma, although most patients with short term follow up remained well
Case reports
Treatment
  • Specific treatment is not indicated for proliferative lesions with apocrine metaplasia
  • Surgical excision of apocrine cysts is not indicated unless there is bloody fluid, the cysts reform or there is atypia in the cytologic specimen
  • Atypical apocrine metaplasia warrants a clinical evaluation comparable to that of women with other atypical proliferative lesions, yet the precancerous significance of this abnormality remains uncertain
Gross description
Microscopic (histologic) description
  • Cells are enlarged with abundant eosinophilic cytoplasm and apical snouts
  • Supranuclear vacuoles or eosinophilic granules may be present
  • Nuclei are round with variable size, vesicular chromatin with prominent nucleoli
  • Can be a single or multiple layer epithelium; even papillary configurations can be seen (papillary apocrine change)
  • Apocrine cells can show a degree of nuclear variability, even in simple epithelium; this is partly a product of cross cutting of a large nucleus and partly an intrinsic property of apocrine epithelium
  • Moderate degrees of nuclear variation and atypia are ignored unless there is necrosis or significant mitotic activity (J Clin Pathol 2007;60:1313)
  • Cytologic atypia tends to be more severe in sclerosing adenosis
  • Highly complex architecture with cytologic atypia should be categorized as atypical ductal hyperplasia or ductal carcinoma in situ
Microscopic (histologic) images

Contributed by Carlos C. Diez Freire, M.D.

Dilated eosinophilic glands

Papillary projections


Abundant cytoplasm

Early apocrine metaplasia and p63

Cytology description
  • Nuclei of benign apocrine cells are eccentrically located with slight variation in size; the nuclear membrane is smooth with fine granular dispersed chromatin and a single prominent nucleolus
  • Cytoplasm is abundant and dense with distinct cell borders with diffuse finely granular cytoplasm that stains pink / blue in PAP stains and purple / gray in Romanowsky stains
  • Atypical apocrine cells can include nuclear enlargement, pleomorphism, prominent nucleoli and cellular dyshesion
  • Features more concerning for carcinoma include crowded cell clusters, more pleomorphism, irregular nuclear borders, dark clumpy chromatin and increased nuclear to cytoplasmic ratio and necrosis
  • Be cautious in a diagnosis of malignancy when atypical apocrine cells occur together with benign cells or if the lesion is clinically or mammographically benign (Demay: The Art & Science of Cytopathology, 2nd Edition, 2011)
Positive stains
Negative stains
Electron microscopy description
  • Abundant endoplasmic reticulum, numerous mitochondria, intermediate filaments and secretory vesicles in the cytoplasm
Molecular / cytogenetics description
Sample pathology report
  • Left breast, 2 o’clock, 5 cm from nipple, ultrasound guided core biopsy:
    • Papillary apocrine metaplasia and duct dilation
Differential diagnosis
Board review style question #1
Apocrine metaplasia of the breast is characterized by

  1. Dilation of terminal ducts with periductal fibrosis and chronic inflammation
  2. Enlarged epithelial cells with abundant granular eosinophilic cytoplasm that can show apical snouting, eccentrically located nuclei with prominent nucleoli
  3. Monotonous population of histiocytes with foamy cytoplasm distending the ducts
  4. Severely atypical and pleomorphic cells of mesenchymal origin
Board review answer #1
B. Apocrine metaplasia of the breast is characterized by enlarged epithelial cells with abundant granular eosinophilic cytoplasm that can show apical snouting, eccentric nuclei and prominent nucleoli.

Reference: Apocrine metaplasia of breast

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Board review style question #2


The histologic findings in the above breast images are an example of

  1. Apocrine metaplasia
  2. Intraductal papilloma
  3. Mammary duct ectasia
  4. Papillary ductal carcinoma in situ
Board review answer #2
A. Apocrine metaplasia. Cells are enlarged with abundant eosinophilic cytoplasm and apical snouts. Supranuclear vacuoles or eosinophilic granules may be present. Nuclei are round with variable size, vesicular chromatin with prominent nucleoli. Can be a single or multiple layer epithelium, even papillary configurations can be seen (papillary apocrine change).

Reference: Apocrine metaplasia of breast

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