Unusual Clinical Presentation of Carcinoma
911
Pathology of the Occult Primary Carcinoma
The primary tumor in more than 90% of cases is a form of
usual IDC that is accompanied by intraductal carcinoma in
most instances.
149,151
The histologic characteristics of the
primary tumor and nodal metastases are similar (Fig. 33.12).
A striking characteristic of many of the primary lesions,
particularly tumors too small to be palpable, is a promi
nent lymphocytic reaction in and around the lesion
133,138
(Figs. 33.13, 33.14, and 33.20). This is especially conspicuous
when the primary lesion appeared to be largely or entirely
in situ
.
An exceptionally high proportion of the occult primary
duct carcinomas have apocrine cytology, and there is a ten
dency for cytoplasmic clearing in the primary lesions as well
as in the metastases (Figs. 33.12 and 33.13). The invasive car
cinomas tend to be poorly differentiated histologically and
cytologically. The data presented in Table 33.2 show some
cases in which the only carcinoma detected in the breast
appeared to be noninvasive. This phenomenon has been
described in several studies.
131,140,167,169
It is thought that me
tastases in these cases arose from invasive carcinoma that
was inapparent with the light microscope amid the
in situ
lymph node obscured by metastatic tumor. Tissue around
the tumor should be studied for evidence of axillary breast
tissue. If found, this is presumptive evidence in support of
an axillary primary, but it is necessary to find
in situ
car
cinoma in conjunction with an invasive axillary lesion to
establish a diagnosis of carcinoma arising in axillary breast
tissue.
Benign lesions that may be associated with ALNs, such
as nevus cell aggregates and heterotopic glands, should not
be misinterpreted as metastatic carcinoma.
166
For further in
formation about heterotopic mammary tissue in ALNs and
nodal nevus cell aggregates, see Chapter 43.
ER and PR have been examined in axillary nodal me
tastases from patients with occult carcinoma.
129,135,163,167,168
The largest series presented similar results, with 32% to
35% of nodal metastases positive for ER and PR, 24% to
27% positive for ER and negative for PR, and 38% to 44%
negative for both receptors.
129,135
Others have also reported
that ER and PR were negative in the majority of ALNs ana
lyzed.
136
Lu et al.
151
reported that about one-third of the
metastatic carcinomas were triple-negative. The presence
of ER is highly suggestive of, but not specific for, mammary
carcinoma.
FIG. 33.18.
Axillary nodal metastases that resemble
intraductal carcinoma.
All images are from cases of oc-
cult carcinoma presenting as axillary nodal metastases.
A:
Round, “solid” aggregates of metastatic ductal car-
cinoma.
B:
Necrosis and calcification in intraductal-like
metastatic carcinoma.
C:
Metastatic apocrine cribriform
carcinoma with peritumoral fibrosis that resembles a
basement membrane.
