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

sclerosing adenosis wherein the stroma shows extensive myoid metaplasia.
Chondrolipoma are benign lesions composed of an admixture of fat, cartilage, and
sometimes bone (122-124).
Leiomyoma usually involves the nipple but is occasionally seen within the breast
substance. Some have been reported to have epithelioid features and granular changes
(125). Benign peripheral nerve tumors of both schwannoma (126) and neurofibroma
types occur in the breast.
Another benign spindle-cell lesion that can occur in the breast is inflammatory
myofibroblastic tumor, a lesion distinct from post-operative myofibroblastic repair
reaction and traumatic fat necrosis, although the latter two can be mistaken for
spindle-cell carcinoma. My colleagues and I (127) recently encountered three patients
who developed firm, mobile, non-tender masses in their breasts. Two were discovered
by the patients and one following mammography. Macroscopically, the nodules were
firm, circumscribed, yellow on cut sections, and composed of interlacing cytologically
bland; spindle cells admixed with chronic inflammatory cells, (the latter
predominantly of lymphocytes and plasma cells). Immunohistochemistry yielded
strong, smooth-muscle actin (SMA) reactivity within the spindle cells; two lesions
were negative for pankeratin, one was focally and weakly positive. No lesions were
positive for anaplastic lymphoma kinase (ALK-1), desmin, S100, CD34, CD21, or
CD35. In each case, a diagnosis of inflammatory myofibroblastic tumor was made
(a.k.a., inflammatory pseudotumor). Following conservative excision with apparently
negative margins, there has been only been a single recurrence in one patient after
three months. The latter recurrence was managed successfully with a second excision
(127).
B. Malignant Spindle-cell Lesions of the Breast: Phyllodes tumors (cystosarcoma
phyllodes) are rare breast neoplasms (0.3% of all tumors) that represent up to 2.5% of
all fibroadenomatous breast lesions (128). Phyllodes tumor is composed of mixed
epithelial and stromal elements, which makes it difficult to clearly distinguish it from
typical fibroadenoma at one end of the spectrum and soft tissue sarcomas at the other.
Phyllodes tumors of the breast present as circumscribed, slow-growing masses ranging
widely from 1 to 30 cm or more. Reported average sizes vary from 4 to 8 cm, with
malignant forms being larger (129). In one series, the age of patients ranged from 9 to
88 years (a mean of 44 years with 80% between 31 and 60 years) (128). They are rare
in patients younger than 20 years (64-71). Moreover, like fibroadenoma, phyllodes
tumors occur only rarely in men (130, 131).
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