Unusual Clinical Presentation of Carcinoma
917
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
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
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.)
