Breast

Other invasive carcinoma subtypes, WHO classified

Acinic cell carcinoma



Last staff update: 27 March 2024 (update in progress)

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PubMed search: Acinic cell carcinoma

Thomas Sabljic, M.D., M.Sc., Ph.D.
Miralem Mrkonjic, M.D., Ph.D.
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Cite this page: Sabljic T, Mrkonjic M. Acinic cell carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastmalignantaciniccellcarcinoma.html. Accessed March 29th, 2024.
Definition / general
  • Acinic cell carcinoma is a malignant epithelial neoplasm characterized by clear and granular cells that may contain zymogen granules in the cytoplasm and shows microglandular and solid growth patterns
Essential features
  • Granular eosinophilic and basophilic cytoplasm with intracytoplasmic granules that are positive for periodic acid-Schiff with diastase (PASD)
  • Infiltrative microglandular and solid growth patterns
  • Positive immunohistochemical staining for EMA and markers of serous acinar differentiation
Terminology
  • Acinar cell carcinoma
ICD coding
  • ICD-O: 8550/3 - acinar cell carcinoma
  • ICD-11: 2C60 & XH3PG9 - carcinoma of breast, specialized type & acinar cell carcinoma
Epidemiology
Sites
Pathophysiology
Etiology
  • Unknown
Clinical features
  • Presentation is similar to invasive breast carcinoma of no special type, palpable mass (Pathology 2017;49:215)
Diagnosis
Radiology description
  • Poorly defined lump / mass with microcalcifications, although may vary in clinical and radiological appearance (Breast 2022;66:208)
Radiology images

Contributed by Miralem Mrkonjic, M.D., Ph.D.
Left breast mass with nonmass enhancement

Left breast mass with nonmass enhancement



Images hosted on other servers:
Doppler ultrasound, molybdenum target

Doppler ultrasound, molybdenum target

MRI and PET / CT

MRI and PET / CT

Prognostic factors
Case reports
Treatment
  • Breast conserving surgery or mastectomy, generally with sentinel lymph node excision or axillary lymph node dissection; with or without neoadjuvant or adjuvant chemotherapy and radiotherapy, hormonal therapy (if ER positive) (Breast 2022;66:208)
Gross description
Gross images

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Ill defined, slightly lobulated mass

Ill defined, slightly lobulated mass

Gray-brown rubbery tumor

Gray-brown rubbery tumor

Microscopic (histologic) description
  • Cells with serous differentiation containing zymogen granules in the cytoplasm that stain with PASD
  • Predominantly solid or microglandular growth but may be cystic, trabecular or show other growth patterns (Breast 2022;66:208)
Microscopic (histologic) images

Contributed by Miralem Mrkonjic, M.D., Ph.D.
Infiltrative growth pattern

Infiltrative growth pattern

Microglandular architecture

Microglandular architecture

Microglandular architecture and eosinophilic cytoplasm

Microglandular architecture and eosinophilic cytoplasm

Areas resembling invasive ductal carcinoma of no special type

Areas resembling
invasive ductal
carcinoma of no
special type

Prominent cytoplasmic eosinophilic granules

Prominent cytoplasmic eosinophilic granules


Background of extensive MGA and AMGA

Background of extensive MGA and AMGA

MGA in the adipose tissue

MGA in the adipose tissue

Nuclear atypia in MGA

Nuclear atypia in MGA

Absence of staining around invasive carcinoma

Absence of staining around invasive carcinoma

Invasive carcinoma is negative for ER

Invasive carcinoma is negative for ER


Invasive carcinoma is negative for HER2

Invasive carcinoma is negative for HER2

Invasive carcinoma is positive for S100

Invasive carcinoma is positive for S100

Invasive carcinoma is positive for lysozyme

Invasive carcinoma is positive for lysozyme

PASD cytoplasmic staining

PASD cytoplasmic staining

Cytology description
  • Fine needle aspiration: hypercellular, atypical cells in sheets, round to oval nuclei, single nucleoli, mild pleomorphism in size, moderately increased N:C ratio, intercellular cystic spaces, acinic pattern, cytoplasmic vacuoles and granules visible on Papanicolaou and Giemsa stains (Cytopathology 2013;24:403)
Positive stains
Negative stains
  • SMA (100% negative, 14/14 cases)
  • ER (90% negative, 59/66 cases)
  • PR (89% negative, 55/62 cases)
  • HER2 (100% negative, 54/54 cases)
  • CK20 (100% negative, 2/2 cases)
  • Reference: Breast 2022;66:208
Electron microscopy description
  • Cells with vacuolated cytoplasm containing many electron dense granules of varying size and a prominent rough endoplasmic reticulum (RER) (J Breast Cancer 2011;14:160)
Electron microscopy images

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Cytoplasmic electron dense granules

Cytoplasmic electron dense granules

Dilation of RER

Dilation of RER

Acinar cell granules, prominent RER

Acinar cell granules, prominent RER

Molecular / cytogenetics description
  • No pathognomonic genomic alterations have been described
  • Has a similar molecular profile to triple negative breast carcinoma and does not share the genomic rearrangement seen in salivary gland acinic cell carcinoma
  • TP53 mutations are the most consistent molecular event (Breast 2022;66:208)
  • PIK3CA and other mutations have been described in a subset of cases (Mod Pathol 2017;30:69)
  • BRCA1 gene alterations have also been described (BMC Cancer 2013;13:46, Histol Histopathol 2023;38:91)
Sample pathology report
  • Breast (right), lumpectomy:
    • Acinic cell carcinoma (see comment)
    • Comment: Sections show breast tissue involved by acinic cell carcinoma in solid nests and acini of polygonal cells with granular eosinophilic cytoplasm. These tumor cells display round, uniform nuclei with prominent nucleoli. Periodic acid-Schiff with diastase (PASD) staining demonstrates the presence of zymogen-like granules in the cytoplasm, confirming the acinar differentiation characteristic of this tumor.
Differential diagnosis
Board review style question #1

A premenopausal woman presents with a painless, palpable, slow growing mass in her left breast. Histological examination reveals cells with abundant eosinophilic and basophilic cytoplasm with large coarse PASD+ intracytoplasmic granules and centrally located nuclei with prominent nucleoli, showing an infiltrative microglandular growth pattern. What is the most likely diagnosis?

  1. Acinic cell carcinoma
  2. Angiolipoma
  3. Burkitt lymphoma
  4. Fibroadenoma
  5. Invasive lobular carcinoma
Board review style answer #1
A. Acinic cell carcinoma. These are the features of acinic cell carcinoma (see microscopic image). Answer D is incorrect because fibroadenoma is a fibroepithelial lesion, which is not infiltrative and the epithelial component does not have diffuse acinar morphology. Answer B is incorrect because angiolipoma is a mesenchymal neoplasm comprised of mature adipocytes and blood vessels. Answer E is incorrect because invasive lobular carcinoma lacks cytoplasmic granules and microglandular growth pattern. Answer C is incorrect because Burkitt lymphoma is a non-Hodgkin lymphoma growing in solid sheets with starry sky appearance.

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Reference: Acinic cell carcinoma
Board review style question #2

Which immunostain expression would be the most helpful to support the suspected diagnosis?

  1. E-cadherin+
  2. HER2+ (3+)
  3. Lysozyme+
  4. Ki67 > 90%
  5. S100+
Board review style answer #2
C. Lysozyme+. Acinic cell carcinoma is positive for EMA and lysozyme. Answer E is incorrect because S100 is positive in acinic cell carcinoma and angiolipoma, so it would not help in differentiating between these entities. Answer D is incorrect because Burkitt lymphomas and not acinic cell carcinomas have a Ki67 index close to 100%. Answer A is incorrect because E-cadherin positivity is not specific to acinic cell carcinoma. Answer B is incorrect because acinic cell carcinomas are not HER2 amplified.

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Reference: Acinic cell carcinoma
Board review style question #3
Which biomarker profile is typical of acinic cell carcinoma?

  1. ER+, PR+, HER2+
  2. ER+, PR+, HER2-
  3. ER+, PR-, HER2-
  4. ER-, PR-, HER2+
  5. ER-, PR-, HER2-
Board review style answer #3
E. ER-, PR-, HER2-. Acinic cell carcinomas are predominantly triple negative with rare cases showing weak ER positivity. Answer C is incorrect because only rare cases of acinic cell carcinoma have been reported to have weak ER positivity. Answers A, B and D are incorrect because acinic cell carcinoma does not share luminal, HER2 amplified or triple positive biomarker profile.

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Reference: Acinic cell carcinoma
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