Case Two – February 2017

• 73 year old female presented with an erythematous, scaly, and eroded plaque on the right nipple.
• No personal or family history of breast cancer.
• Physical examination failed to reveal a palpable breast mass.
• Biopsy was performed after the lesion was unresponsive to topical corticosteroids.

• Irritant contact dermatitis
• Mammary Paget disease
• Squamous cell carcinoma

• There is a proliferation of enlarged epithelioid cells distributed at all levels of the epidermis in pagetoid array with abundant vacuolated cytoplasm.

• The tumor cells exhibit nuclear pleomorphism and atypical mitotic figures are present.

Immunohistochemistry:

• Positive for EMA and Cam5.2
• Negative for p63, estrogen receptor (ER), progesterone receptor (PR), and mucicarmine

Histologic Differential Diagnosis:

• Mammary Paget disease
• Squamous cell carcinoma in situ with Bowenoid features

“Anaplastic” Mammary Paget Disease

• This variant of mammary Paget disease shows striking cytologic atypia and mimics pagetoid Bowen disease histologically.
• The tumor cells in mammary Paget disease typically show positive staining for CEA, EMA, CK7, Cam5.2 and cytokeratin AE1/AE3.
• The anaplastic variant of mammary Paget disease is often negative for mucin special stains (such as Alcian blue and mucicarmine), which was seen in our case.
• While CK7 is often positive in mammary paget disease, it may also be positive in a subset of squamous cell carcinomas.
• Some examples of anaplastic mammary Paget disease also show acantholysis.
• Clues to the diagnosis of anaplastic mammary Paget disease include the absence of dyskeratotic cells and desmosomes, presence of intracellular mucin/signet ring cells, and positive staining for CEA and EMA.

What is this tumor, and why should I know about it?

• Anaplastic mammary Paget disease can mimic pagetoid Bowen disease histologically.
• The anaplastic variant of mammary paget disease may be associated with an increased risk of underlying invasive carcinoma, even in the absence of a palpable mass.

• Anaplastic Paget disease mimics pagetoid Bowens disease histologically.
• This variant is negative for mucin special stains (Alcian blue and mucicarmine) and may show acantholysis.
• Positive staining for CEA and EMA favor a diagnosis of anaplastic mammary Paget disease over pagetoid Bowen disease.
• Even with the absence of a palpable mass, anaplastic mammary Paget disease may be associated with increased risk of an underlying invasive breast cancer compared to conventional Paget disease.