33 Special Types of Invasive Breast Carcinoma: Diagnostic Criteria ...

adenoma by others who prefer to avoid carcinoma for a group of lesions that mainly
recur after local excision (28a). Both glandular and squamous differentiation coexists
in this very low-garde carcinoma, and a highly infiltrative growth pattern is
responsible for the high local recurrence rate. They are cytologically bland and do not
metastasize to distant sites and some examples have reached 8 cm in diameter. Lymph
node metastatic spread is extremely rare and noted in a single case. Their stroma is
typically "fibromatosis-like" being cellular and composed of bland spindle cells, but
can be collagenous, hyalinized or variably cellular. Some low-grade adenosquamous
carcinomas occur in association with a central sclerosing papillary lesion or sclerosing
adenosis. Low-grade adenosquamous carcinoma lack hormone receptors.
Adenocarcinoma with spindle-cell metaplasia is an unusual invasive duct
adenocarcinoma with abundant spindle cell transformation, and the spindle cells are
glandular in nature. The spindle cells immunoreact with epithelial markers including
CK7, but not with CK5/6 or other markers of squamous/myoepithelial differentiation.
Electron microscopy reveals glandular lumens in the spindle cells. Prognosis is
determined by the size and degree of differention, as well as pathologic stage. Most
occur in postmenopausal women, presenting as discrete masses.
Matrix-producing metaplastic carcinoma is a carcinoma with direct transition to a
cartilaginous or osseous stromal matrix without an intervening spindle cell zone or
osteoclastic cells (1). More commonly, the heterologous areas develop from a spindlecell
component. Metaplastic cells in the osseous and cartilaginous matrix stain for S-
100 protein and vimentin, with variable and sometimes negative reactivity for keratin
and epithelial membrane antigen. Metastases derived from a metaplastic carcinoma
may be entirely adenocarcinoma, entirely metaplastic, or a mixture of both. A
minority of axillary metastases actually contain heterologous components, but they are
found more commonly in local recurrences on the chest wall and in visceral
metastases (8, 19). Davis and coworkers (29) studied 22 patients with metaplastic
carcinoma of the breast with pure or almost pure sarcomatoid morphology. Patients
were included in the study if their tumors had sarcomatoid morphology and: 1) an
invasive carcinomatous component identifiable on hematoxylin and eosin stains
comprising less than 5% of the invasive tumor; or 2) associated ductal carcinoma in
situ; or 3) immunohistochemical expression of keratin in the sarcomatoid areas.
Axillary lymph node dissection or limited axillary node excision was performed in 17
patients, including 1 patient who had a sentinel lymph node biopsy. Lymph node
involvement occurred in only 1 patient and consisted of a single 3.5-mm metastasis.
Clinical follow-up was available for 21 patients and ranged from 4 months to 155
months (median follow-up, 35 months). Ten patients experienced local relapse,
including 7 of 11 patients treated with breast-conserving surgery, and 9 developed
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