Reactive and Inflammatory Conditions of the Breast

Clinical Presentation

Mammary duct ectasia has been reported by many other descriptors (e.g., varicocele tumor, comedo-mastitis, periductal mastitis, plasma cell mastitis, stale-milk mastitis, chemical mastitis, granulomatous mastitis, and mastitis obliterans) ( Fig. 2.1 ).

Most cases occur in premenopausal parous women, possibly caused by duct obstruction and/or triggered by different components of stagnant colostrum. Mammary duct ectasia may produce retraction or inversion of the nipple, and nipple discharge is present in approximately 20% of patients.

Microscopic Pathology

This is a disorder that affects large ducts of the breast, so there is ectasia of large ducts, with accumulation of detritus in the lumen and fibrous thickening of the wall containing an increased amount of elastic fibers. Calcification is common, producing tubular, annular, and linear shadows on the mammogram. There is no epithelial hyperplasia or apocrine metaplasia. If there is epithelial denudation, the luminal material may escape from the duct, and a florid inflammatory reaction results, which is rich in macrophages and plasma cells. Mammary duct ectasia affecting medium and smaller ducts often shows denuded epithelium, macrophages in the lumen, and lymphocytic cuffing around the fibrotic wall.

In advanced stages of mammary duct ectasia, fibrous obliteration of the ducts can occur. Indeed, ductitis obliterans or mastitis obliterans is a rare, late manifestation of mammary duct ectasia. Wang and coworkers reported a long-term diabetic patient who presented with bilateral bloody nipple discharge and poorly defined nodularities around the nipples of both breasts. The ductography showed multiple segments of irregular ductal narrowing and intraluminal filling defects in both breasts. The bilateral resection of the subareolar portion of the breast showed exuberant fibrous obliteration of the large- and medium-sized ducts by granulation tissue associated with few histiocytes. Ductal dilatation and intraductal accumulation of histiocytes were also present. This represents a late and florid form of mammary duct ectasia.

Treatment and Prognosis

Excision biopsy should be curative. Recurrence is uncommon.

Differential Diagnosis

Differential diagnostic considerations include fibrocystic changes, diabetic sclerosing lymphocytic lobulitis, idiopathic granulomatous lobular mastitis, and periareolar abscess (Zuska disease). Accurate diagnosis can help avoid or limit radical surgeries in this group of patients. Mammary duct ectasia is likely unrelated to fibrocystic disease, but duct ectasia may be related to breast abscesses, which usually result from rupture of mammary ducts. They most often occur during lactation but also independently from it. Abscesses may also be located deep within the parenchyma or periareolar region. Microscopically, a central cavity filled with neutrophils and secretion is surrounded by inflamed and eventually fibrotic breast parenchyma with obliteration of the lobular pattern. Clinically, a localized abscess may simulate carcinoma. Periareolar abscess associated with squamous metaplasia of lactiferous ducts (SMOLDering breast disease) is referred to as Zuska disease. SMOLDering breast disease requires surgical excision to effect cure.

Clinical Presentation

Clinically significant fat necrosis is most likely of traumatic origin, and it often involves the superficial subcutaneous tissue rather than the breast parenchyma itself ( Fig. 2.2 ). A history of trauma can be elicited in about half of cases, usually 1 to 2 weeks before the time of diagnosis. In some cases, prior biopsy or surgical site continues to undergo fat necrosis presenting months and, rarely, years later as an enlarging spiculated lesion on imaging studies. Cases of mammary fat necrosis have also been reported after radiation therapy and as a local manifestation of Weber-Christian disease.

Gross Pathology

The disease can simulate carcinoma because of skin retraction and the scirrhous (stellate scar–like) nature of the reparative response. The lesions may be gray-white or orange-brown, depending on the deposition of hemoglobin-derived pigments.

Microscopic Pathology

The microscopic diagnosis is usually easy, but the frozen section may cause some difficulty. Traumatic fat necrosis shows variable and irregular stellate fibrosis, occurring around areas of necrotic, variably vacuolated fat with abundant admixed foamy macrophages. In later stages, calcifications are commonly seen.

Treatment and Prognosis

Fat necrosis is a benign disease, which should be cured by excision.

Differential Diagnosis

Foamy macrophages are uncommon in carcinoma, and they are the clue to the correct diagnosis. Cytokeratin immunocytochemistry stains should help in difficult cases. Rare histiocyte-like variants of lobular carcinoma occur and should be ruled out.

Clinical Presentation

Granulomatous lobular mastitis causes a breast mass, sometimes mimicking carcinoma, in women of child-bearing age. It is characterized by multiple, chronic-active, necrotizing, granulomatous abscesses centered on the segmental ducts and attached lobules, yielding a lobulocentric disease pattern ( Figs. 2.3 and 2.4 ). Women with granulomatous lobular mastitis are usually parous (often within 5 years of pregnancy) or on oral contraceptive therapy.

Gross Pathology

It presents as a gray-tan mass lesion, which is irregular, and often mimics invasive carcinoma.

Microscopic Pathology

The inflammatory changes are characterized by destructive, necrotizing, granulomatous inflammation involving numerous polymorphonuclear leukocytes, multinucleated giant cells, and focal lipogranuloma-like changes. Lobulocentric abscesses develop in adjacent segmental ducts and terminal duct lobular units with relative sparing of interlobular stroma.