Rosen's Breast Pathology, 4e

359

Ductal Carcinoma In Situ

FIG. 11.34.  DCIS, solid. A: The duct is filled by a compact growth of carcinoma cells with pleomor- phic nuclei of intermediate nuclear grade. B: Solid apocrine DCIS with clear cell change.

Some examples of spindle cell DCIS are variants of pap- illary DCIS, but spindle cell growth can be encountered in nonpapillary DCIS (Fig. 11.36). Small cell DCIS occurs in as- sociation with invasive small cell (oat cell) carcinoma (see Chapter 21) or as an isolated lesion (Fig. 11.37). DCIS arising in SA assumes the structural configuration of the underlying adenosis and may be mistaken for invasive carcinoma. 136–139 (Fig. 11.38). The majority of these patients are premenopausal. Because SA is fundamentally a lesion formed by altered lobules, this presentation can be viewed as a form of intralobular extension of the ductal lesion. The condition usually occurs focally rather than diffusely and is diagnosed when the proliferative epithelium has the struc- tural and cytologic appearance of DCIS. The growth patterns are usually solid and cribriform (Figs. 11.38 and 11.39). An organoid appearance may result from the alveolar expansion of lobular structures in the adenosis. Microcalcifications may be present in the underlying adenosis or as part of the

DCIS. DCIS can be limited to the SA, or there may be foci in the surrounding breast. 137 The underlying architecture of SA can be appreciated with stains for basement membranes such as PAS, reticulin, or lam- inin, and immunostains to identify myoepithelial cells such as p63, calponin, CD10, and SMA. 137,139 The antibody for SMM- HC is useful in this circumstance because it is likely to avoid most of the obscuring effect produced by actin reactivity in myofibroblasts encountered with other antiactin antibodies (Fig. 11.39). Rarely, invasive carcinoma can have an adenosis- like pattern that is difficult to distinguish from DCIS in ad- enosis. In this situation, stains for myoepithelium are useful. Absence of myoepithelium is diagnostic of invasive carcinoma. Invasive carcinoma arising in SA is difficult to detect un- less the invasive component has clearly grown beyond the area of adenosis and has an architectural pattern that differs from that of the adenosis (Figs. 11.40 and 11.41). A double immu- nostain for cytokeratin and actin can be helpful for identifying

FIG. 11.35.  DCIS, solid. A: Apocrine type of solid DCIS with loss of cohesion, with central necro- sis ( inset ). The histopathologic appearance simulates pleomorphic LCIS. B: DCIS in (A) is strongly E-cadherin positive, supporting ductal differentiation.