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We evaluated the low affinity neurotrophin receptor (p75NTR) as a marker of breast myoepithelial cells. Immunohistochemical staining for p75NTR was performed on paraffin sections of 122 malignant breast lesions, 28 benign lesions and the adjacent normal breast tissue. The staining pattern was compared to those of myosin heavy chain and p63. p75NTR immunostain was consistently positive and compatible with p63 and myosin immunoreactivity in the myoepithelial cells of the normal mammary gland, benign breast lesions (six usual ductal hyperplasias, six specimens with sclerosing adenosis, eight intraductal papillomas, six fibroadenomas), and carcinoma in situ (18 ductal carcinomas in situ, two noninvasive papillary carcinomas, two lobular carcinomas in situ). The luminal cells were negative for p75NTR, but rare positive cells were noticed in the solid areas of some of the usual ductal hyperplasias. Four of 64 invasive ductal carcinomas (6%) and all metaplastic carcinomas (n = 3, 100%) showed a variable degree of p75(NTR) positivity. No p75NTR expression was found in the malignant cells in all in situ carcinomas, invasive lobular carcinomas (n = 11), tubular carcinomas (n = 10), invasive papillary carcinomas (n = 6), mucinous carcinomas (n = 4), and medullary carcinomas (n = 2). No myosin immunoreactivity was seen in the luminal/tumor cells, but p63 pattern of staining in the luminal/tumor cells was quite similar to that of p75NTR. Although significant p75NTR immunoreactivity was noticed in the vessels, nerves, and stromal component of fibroadenomas, no difficulties in the evaluation of the immunostain of myoepithelial cells were encountered. Our study shows that p75NTR is a useful marker for breast myoepithelial cells and can be used to rule out invasive disease as well as to evaluate difficult for diagnosis sclerosing lesions. Our data suggest a role of neurotrophins in the development of fibroepithelial breast tumors and some of the breast carcinomas.

Pseudoangiomatous stromal hyperplasia (PASH) of the mammary gland is a well-known benign localized form of stromal overgrowth with probable hormonal etiology. We describe the histologic findings and immunohistochemistry of two cases. Two women, 16 and 58 years old, presented with a breast mass and underwent surgical excision. Grossly, they consisted of a well-circumscribed, rubbery tissue with a solid white-tan homogeneous cut surface. One of the cases showed focal cystic areas. Histologically the lesion showed a proliferation of the collagenous stroma with varying degrees of density, and hyalinization with many pseudovascular slit-like anastomosing spaces lined by spindle cells with scant cytoplasm and bland chromatin. The spindle cells lining the spaces were strongly reactive for vimentin and weakly reactive for CD34, actin, and desmin. They were negative for factor VIII, S-100, and pankeratin. In PASH, the "pseudoangiomatous" term describes a recognizable pattern but does not describe the tumor's histologic nature. We propose the name nodular myofibroblastic hyperplasia of the mammary stroma as a more accurate name.

We reviewed breast tissue from 19 female postpubertal and three prepubertal patients with cystic fibrosis to determine the histopathologic changes present. Autopsy material was available from 19 patients who died from complications of cystic fibrosis. Two patients had lumpectomies for breast carcinoma and an additional patient had a breast biopsy and bilateral prophylactic mastectomies for breast carcinoma. The postpubertal patients ranged in age from 18 to 50 years (median age, 32 years). The histologic changes in the breast of female patients with cystic fibrosis have not been fully studied, and the only case reported suggests that these patients suffered from complete lobular agenesis. This study shows that postpubertal breasts had normal development and varying degrees of fibrosis affecting lobular units and ducts, and that proliferative lesions and carcinoma could be encountered.