Ductal Carcinoma
In Situ
391
Microinvasion associated with florid and pleomorphic
LCIS may be mistaken for microinvasive
ductal
carcinoma.
In the only series of 16 cases reported to date, ALN biopsies
(including nine SLN samplings) were performed in 13 cases,
with negative results in each, and all patients were alive
without evidence of recurrence or of metastases in a mean
follow-up of 24 months.
313
The foregoing data indicate that microinvasion is more
likely to be found associated with high-grade, clinically
evident DCIS than with low-grade, mammographically de-
tected DCIS. When microinvasion is detected, the frequency
of nodal metastases is 10% or less in patients who undergo
axillary dissection, and the probability of systemic metasta-
ses is 5% or less. Axillary dissection can be avoided in mi-
croinvasive duct carcinoma if SLN biopsy is performed. This
procedure adds greater precision with less morbidity to the
detection of axillary nodal metastases.
SENTINEL LYMPH NODE BIOPSY
SLN biopsy is used to assess axillary nodal status in patients
with invasive and
in situ
carcinoma. Routine use of SLN is
generally not employed in DCIS, except when there is exten-
sive high-grade DCIS, when invasive carcinoma is suspected,
or when mastectomy is performed.
314
The incidence of nodal
involvement in patients with DCIS has been reported to
range from 0.5% to 1.5%, respectively
253
; however, SLN posi-
tivity can be higher in higher grade and more widespread
DCIS. In a set of 854 DCIS cases treated at the European
Institute of Oncology over more than a decade-long period
ending 2006, SLN involvement was detected in 12 (1.4%),
consisting of seven cases with micrometastases (less than
0.2 mm) and four patients with isolated tumor cells (ITC).
315
None of the 11 patients who underwent subsequent axillary
dissection had additional nodal involvement.
316
Zavotsky et al.
317
found metastatic carcinoma in the SLN
from 2 (14.3%) of 14 patients with DCIS. Completion axil-
lary dissection revealed no other nodal metastases. Dauway
et al.
318
cited nine patients with microinvasive carcinoma as-
sociated with DCIS (T1
mic
). Three (33%) of these patients
had micrometastases detected in an SLN by cytokeratin IHC
and no other metastases in a completion axillary dissection.
These investigators also reported that 5 (6%) of 86 patients
with lesions classified as DCIS had metastases in an SLN.
Four of the nodal metastases were detected only by cytokera-
tin IHC. Four of the five patients had “comedo” DCIS, and
the fifth had a 9.5-cm low-grade micropapillary and cribri-
form lesions. Completion axillary dissection in four cases
yielded no additional metastases.
Several additional studies have examined the yield of
SLN mapping in intraductal and microinvasive ductal carci-
noma. Wilkie et al.
319
found a positive SLN in 27 (5%) of 559
patients with DCIS. Nineteen (70%) of the 27 positive SLNs
were detected by IHC. Among 51 women with microinva-
sive ductal carcinoma, 7 (14%) had a positive SLN, 5 (71%)
of which were immunohistochemical findings.
Katz et al.
320
reported finding a positive SLN associated
with 8 (7.2%) of 110 breasts with DCIS. In four of these
comedocarcinomas. One of the 28 patients (4%) with micro-
invasive carcinoma had ALN metastases.
Silver and Tavassoli
308
defined microinvasion as “a single
focus of invasive carcinoma less than or equal to 2 mm or
up to three foci of invasion, each less than or equal to 1 m
in greatest dimension” in a study of 38 patients. “Comedo”
DCIS was present in 31 (82%), and papillary or other types
of DCIS were present in 7 (18%). All patients were treated
by mastectomy with axillary dissection, and no lymph node
metastases were found. After a mean follow-up of 7.5 years,
no patient had developed recurrent breast carcinoma.
de Mascarel et al.
309
subclassified microinvasive duct car-
cinoma into type 1 (single tumor cells) and type 2 (clusters of
tumor cells). Type 1 cases would qualify for classification as
T1mic
, as would some type 2 cases. Among a subset of 20 type 2
cases that weremeasured, 6were T1
mic
and 14 had invasive foci
of between 2 and 10 mm. None of the 59 type 1 patients who
had ALNs removed had nodal metastases. On the other hand,
there were nodal metastases in 14 (10%) of the 139 patients with
type 2 microinvasion who had ALNs examined. Distant me-
tastases were reported in 2 (3%) of the 72 patients with type 1
microinvasion and in 12 (7%) of 171 with type 2microinvasion.
The survival of patients with type 1 microinvasive carcinoma
was similar to that of patients with pure DCIS and significantly
better than that of patients with type 2 microinvasion.
Information about patients with microinvasion defined
as T1
mic
(less than 1 mm) are becoming increasingly avail-
able. Jimenez and Visscher
310
described 75 patients with mi-
croinvasion, defined as one focus less than 5 mm or multiple
foci with an aggregate diameter of less than 10 mm. Two or
more histologically separate foci of invasion were present in
59% of the cases. Microinvasion consisting of isolated cell
clusters less than 1 mm was present in 25 cases (33%). ALN
dissection performed in 69 cases revealed metastatic carci-
noma in five (7%). Two of these patients had invasive foci
measuring less than 1 mm (T1
mic
), and in a third case the
invasive lesion measured 1.1 mm.
Walker et al.
311
compared the clinical and pathologic fea-
tures of DCIS detected by mammography to patients who
had symptoms, usually a mass or nipple discharge. Micro-
invasion (T1
mic
) was found in 5 (5%) of 92 mammographi-
cally detected and in 10 (13.5%) of 74 symptomatic cases. All
but 1 of the 15 DCIS lesions with microinvasion were larger
than 2 cm. Most DCIS with microinvasion had a comedo
growth pattern or necrosis and high nuclear grade.
By using a double immunostaining procedure for actin
and cytokeratin, Prasad et al.
312
were able to confirm mi-
croinvasion (T1
mic
) in 21 of 109 cases originally diagnosed
as microinvasion or in which microinvasion was suspected.
Eighteen lesions were ductal and three were lobular. The car-
cinoma had high nuclear grade and necrosis in 16 of the 18
(89%) ductal lesions, including 13 (72%) described as comedo
type. Axillary dissection performed in 15 patients revealed
metastatic carcinoma in two cases, each with one lymph node
involved. One of the 18 patients had recurrent carcinoma in
the same breast after conservation surgery and radiotherapy,
and another developed a chest wall recurrence of invasive
duct carcinoma after a mastectomy. There were no systemic
metastases after a median follow-up of 28 months.
