Breast

Epithelial tumors

Invasive breast carcinoma
• Infiltrating duct carcinoma, NOS 8500/3
• Oncocytic carcinoma 8290/3
• Lipid rich carcinoma 8314/3
• Glycogen rich carcinoma 8315/3
• Sebaceous carcinoma 8410/3
• Lobular carcinoma, NOS 8520/3
• Tubular carcinoma 8211/3
• Cribriform carcinoma, NOS 8201/3
• Mucinous adenocarcinoma 8480/3
• Mucinous cystadenocarcinoma, NOS 8480/3
• Invasive micropapillary carcinoma of breast 8507/3
• Metaplastic carcinoma, NOS 8575/3

Rare and salivary gland type tumors
• Secretory carcinoma 8502/3
• Acinar cell carcinoma 8550/3
• Mucoepidermoid carcinoma 8430/3
• Polymorphous adenocarcinoma 8525/3
• Adenoid cystic carcinoma 8200/3
  • Classic adenoid cystic carcinoma
  • Solid basaloid adenoid cystic carcinoma
  • Adenoid cystic carcinoma with high grade transformation
• Tall cell carcinoma with reversed polarity 8509/3

Neuroendocrine neoplasms
• Neuroendocrine tumor, NOS 8240/3
• Neuroendocrine tumor, grade 1 8240/3
• Neuroendocrine tumor, grade 2 8249/3
• Neuroendocrine carcinoma, NOS 8246/3
• Neuroendocrine carcinoma, small cell 8041/3
• Neuroendocrine carcinoma, large cell 8013/3

Epithelial myoepithelial tumors
• Pleomorphic adenoma 8940/0
• Adenomyoepithelioma, NOS 8983/0
• Adenomyoepithelioma with carcinoma 8983/3
• Epithelial myoepithelial carcinoma 8562/3

Noninvasive lobular neoplasia
• Atypical lobular hyperplasia
• Lobular carcinoma in situ, NOS 8520/2
  • Classic lobular carcinoma in situ
  • Florid lobular carcinoma in situ
  • Lobular carcinoma in situ, pleomorphic 8519/2

Ductal carcinoma in situ (DCIS)
• Ductal carcinoma, noninfiltrating, NOS 8500/2
  • DCIS of low nuclear grade
  • DCIS of intermediate nuclear grade
  • DCIS of high nuclear grade

Benign epithelial proliferations and precursors
• Usual ductal hyperplasia
• Columnar cell lesions including flat epithelial atypia
• Atypical ductal hyperplasia

Adenosis and benign sclerosing lesions
• Sclerosing adenosis
• Apocrine adenoma 8401/0
• Microglandular adenosis
• Radial scar / complex sclerosing lesion

Papillary neoplasms
• Intraductal papilloma 8503/0
• Ductal carcinoma in situ, papillary 8503/2
• Encapsulated papillary carcinoma 8504/2
• Encapsulated papillary carcinoma with invasion 8504/3
• Solid papillary carcinoma in situ 8509/2
• Solid papillary carcinoma with invasion 8509/3
• Intraductal papillary adenocarcinoma with invasion 8503/3

Adenomas
• Tubular adenoma, NOS 8211/0
• Lactating adenoma 8204/0
• Duct adenoma, NOS 8503/0

Mesenchymal tumors

Vascular tumors
• Hemangioma, NOS 9120/0
  • Perilobular hemangioma
  • Venous hemangioma
  • Cavernous hemangioma
  • Capillary hemangioma
• Angiomatosis
• Atypical vascular lesion 9126/0
  • Lymphatic atypical vascular lesion resembling lymphangioma
  • Vascular atypical vascular lesion resembling hemangioma
• Postradiation angiosarcoma 9120/3
  • Epithelioid angiosarcoma
• Angiosarcoma 9120/3
  • Epithelioid angiosarcoma

Fibroblastic and myofibroblastic tumors
• Nodular fasciitis 8828/0
• Myofibroblastoma 8825/0
• Desmoid type fibromatosis 8821/1
• Inflammatory myofibroblastic tumor 8825/1

Peripheral nerve sheath tumors
• Schwannoma, NOS 9560/0
• Neurofibroma, NOS 9540/0
• Granular cell tumor, NOS 9580/0
• Granular cell tumor, malignant 9580/3

Smooth muscle tumors
• Leiomyoma, NOS 8890/0
  • Cutaneous leiomyoma
  • Leiomyoma of the nipple and areola
• Leiomyosarcoma, NOS 8890/3

Adipocytic tumors
• Lipoma, NOS 8850/0
• Angiolipoma, NOS 8861/0
• Liposarcoma, NOS 8850/3

Other mesenchymal tumors and tumor-like conditions
• Pseudoangiomatous stromal hyperplasia

Fibroepithelial tumors
• Fibroadenoma, NOS 9010/0
• Phyllodes tumor, NOS 9020/1
  • Periductal stromal tumor
  • Phyllodes tumor, benign 9020/0
  • Phyllodes tumor, borderline 9020/1
  • Phyllodes tumor, malignant 9020/3
• Hamartoma

Tumors of the nipple
• Nipple adenoma 8506/0
• Syringoma, NOS 8407/0
• Paget disease of the nipple 8540/3

Malignant lymphoma
• Diffuse large B cell lymphoma, NOS 9680/3
• Burkitt lymphoma, NOS / acute leukemia, Burkitt type 9687/3
  • Endemic Burkitt lymphoma
  • Sporadic Burkitt lymphoma
  • Immunodeficiency associated Burkitt lymphoma
• Breast implant associated anaplastic large cell lymphoma 9715/3
• Mucosa associated lymphoid tissue lymphoma 9699/3
• Follicular lymphoma, NOS 9690/3

Metastatic tumors

Tumors of the male breast
• Gynecomastia
• Carcinoma
  • Invasive carcinoma 8500/3
  • In situ carcinoma 8500/2

Contributed by Indu Agarwal, M.D., Mirna B. Podoll, M.D. and Julie M. Jorns, M.D.

Which of the following is a new entity in the WHO Classification of Breast Tumours, 5th edition, published in 2019?

1. Malignant phyllodes tumor with well differentiated liposarcomatous differentiation alone
2. Medullary carcinoma
3. Mucinous cystadenocarcinoma
4. Solid papillary carcinoma

C. Mucinous cystadenocarcinoma. Tall cell carcinoma with reversed polarity (TCCRP) and mucinous cystadenocarcinoma, NOS are 2 new entities. TCRRP is a rare subtype of invasive breast carcinoma characterized by tall columnar cells with reversed nuclear polarity, arranged in solid and solid papillary patterns and most commonly associated with IDH2 p.Arg172 hotspot mutations. Mucinous cystadenocarcinoma of the breast is an invasive breast carcinoma characterized by cystic structures lined by tall columnar cells with abundant intracytoplasmic mucin, resembling pancreatobiliary or ovarian mucinous cystadenocarcinoma.

Answer A is incorrect because liposarcomatous differentiation has been removed as a histologic criterion for malignancy in phyllodes tumor in the absence of additional supporting features. Answer B is incorrect because tumors previously called as medullary carcinoma, atypical medullary carcinoma and invasive carcinoma with medullary features have been subsumed into a combined morphologic subset under the category of invasive carcinoma, NST with basal-like and medullary pattern, regarding them as a part of a spectrum of tumor infiltrating lymphocytes rich breast carcinomas. Answer D is incorrect because encapsulated papillary carcinoma and solid papillary carcinoma have been previously present in prior WHO editions.

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Reference: Breast - WHO classification

Tall cell carcinoma with reversed polarity (TCCRP) is a new entity in the WHO Classification of Breast Tumours, 5th edition, published in 2019, that has what typical prognosis and estrogen receptor (ER), progesterone receptor (PR) and HER2 / neu (HER2) profile?

1. Good prognosis, ER / PR negative, HER2 negative
2. Good prognosis, ER / PR positive, HER2 negative
3. Poor prognosis, ER / PR negative, HER2 negative
4. Poor prognosis, ER / PR positive, HER2 negative

A. Good prognosis, ER / PR negative, HER2 negative. Tall cell carcinoma with reversed polarity (TCCPR) is a rare subtype of invasive breast carcinoma characterized by tall columnar cells with reversed nuclear polarity, arranged in solid and solid papillary patterns and most commonly associated with IDH2 p.Arg172 hotspot mutations. Despite the good prognosis and indolent course of TCCRP, this tumor typically expresses low and high molecular weight keratins, including CK5/6 and is ER / PR and HER2 negative, thus part of a group of rare good prognosis triple negative breast carcinoma (TNBC), which also includes some salivary gland type tumors (e.g., adenoid cystic carcinoma) and variants of metaplastic carcinoma (e.g., low grade fibromatosis-like carcinoma). Answers B and D are incorrect because TCCRP is not ER / PR positive. Answers C and D are incorrect because it is not a poor prognosis breast cancer subtype.

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Reference: Breast - WHO classification