Rosen's Breast Pathology, 4e

917

Unusual Clinical Presentation of Carcinoma

FIG. 33.23.  Occult carcinoma, lymph node status and survival. Kaplan–Meier survival rate comparison of patients stratified for the number of involved lymph nodes. The differences are not statistically significant; ( left ) one to three positive nodes, ( right ) four or more positive nodes. (Reproduced with permission from Rosen PP, Kimmel M. Occult breast carcinoma presenting with ALN metastases: a follow-up study of 48 patients. Hum Pathol 1990;21:518–523. Copyright W.B. Saunders Co.)

IDC that arose in ectopic vulvar mammary tissue. A woman reported by Guerry et al. 193 had asynchronous bilateral mam­ mary carcinomas and a separate primary mammary-type ad­ enocarcinoma that arose in ectopic vulvar breast tissue. Goyal et al. 196 described a patient with a history of locally advanced disease because of an axillary mass thought clinically to be nodal metastases that proved to be benign axillary breast tis­ sue. Breast carcinoma has been reported in a patient with a history of familial functional axillary breast tissue. 197 The most frequent site of ectopic breast tissue is in the ­axilla, mainly affecting women 40 years of age or older (28 to 90 years). 198 Separate primary carcinomas arising concur­ rently in ectopic axillary breast tissue and in the ipsilateral breast are an extremely unusual coincidence. 199 Anterior chest wall locations include the parasternal, subclavicular, and inframammary locations. 199–201 In one case, a 46-­year-old woman was found to have a 1.2-cm E-cadherin–negative ER-positive infiltrating pleomorphic lobular carcinoma that arose in ectopic breast tissue on the inframammary anterior chest wall. 201 ALN mapping yielded metastatic carcinoma in a SLN with extranodal extension. No carcinoma was clini­ cally ­evident in either breast. Carcinoma originating in ecto­ pic breast tissue has been described in the subclavicular and ­anterior ­axillary regions, over the sternum, and in the upper abdominal skin outside the distribution of themilk lines. 202–204 Histologically, most adenocarcinomas arising in ectopic breast tissue have had a ductal growth pattern. Infrequent examples of medullary, papillary, 202 and infiltrating lobu­ lar carcinoma have been reported (Fig. 33.24). 199–201 The

­extraordinary occurrence of secretory carcinoma arising in ectopic breast tissue in an adult patient has been described. 205 Ectopic breast tissue, especially when located in the axilla, may be distributed in subcutaneous tissue and the deep der­ mis of the skin (Fig. 33.25). The breast tissue may mingle with normal skin appendage glands rather than forming a discrete, independent structure. In this circumstance it can be difficult to distinguish between carcinoma of mammary and skin ap­ pendage gland origin. 206 The diagnosis of carcinoma arising in ectopic axillary breast tissue beyond the usual anatomic extent of the breast can be made if intraductal and/or invasive carcinoma are found in subcutaneous mammary glandular parenchyma beyond the normal extent of the breast. The distinction between breast tissue remaining after mastectomy and ectopic breast tissue depends largely upon location. Residual breast tissue, not necessarily ectopic in its distribution, is a potential source for a new primary carcinoma on the chest wall after mastectomy. 207,208 The presence of noncarcinomatous breast tissue and/or an in situ component will distinguish such a new primary from a conventional cutaneous local recurrence. It is essential that a lesion labeled clinically as a “local recurrence” at the site of a prior mastectomy be carefully examined histologically for evidence of residual breast tissue and in situ carcinoma (Fig. 33.26). The presence of the latter features indicates that the tumor is probably a new primary carcinoma with a clinical course determined by its specific histologic and biologic properties. Rarely, there may be substantial differ­ ences in histologic features between the initial carcinoma