33 Special Types of Invasive Breast Carcinoma: Diagnostic Criteria ...

irregular margin suggests the presence of invasion.
Some papillary carcinomas contain Grimelius and chromogranin-positive cells
(neuroendocrine differentiation), which have not been found in papillomas (28). In
some parts of the tumor the cell proliferation becomes so dense that basic papillary
properties are obscured. Such a tumor is described as having a solid papillary pattern
(28,29). Moreover, there is a broad range of mucin secretion, which can be marked in
some cases; this feature is highly associated with concomitant neuroendocrine
differentiation and, sometimes, invasive mucinous carcinoma. These solid papillary
carcinomas have been recently reviewed (30). The authors reported that solid papillary
carcinomas (SPCs) are uncommon tumors composed of circumscribed large cellular
nodules separated by bands of dense fibrosis. Fifty-eight SPCs were analyzed (mean
follow-up, 9.4 years). Cases were divided into three groups: 1) SPC only (32.7%), 2)
SPC with extravasated mucin (8.6%), and 3) SPC with invasive components (58.7%)
consisting of neuroendocrine-like (29.5%), colloid (23.5%), ductal not otherwise
specified (14.5%), lobular (3%), tubular (3%) or mixed (26.5%). The mean age was
72 years. All were estrogen receptor positive and 86% were histologic grade 1. The
total size of the tumor measured 0.3 to 15 cm. In the group with invasive carcinoma,
the size of the invasion was 0.1 to 4 cm. Axillary nodes were involved in 13% of the
cases and all of these had an invasive component in the primary tumor. Local
recurrence was seen in 5 patients, all from the group with invasive carcinoma. Overall,
11.7% died of their tumor, 1 to 4 years after diagnosis (mean, 2.3 years); none of them
belong to the group of noninvasive SPC. Five of the 6 patients who died of tumor had
invasive components. The sixth patient who died with “metastatic signet-ring cell
carcinoma” at 10 years was in the group of patients with SPC with extravasated mucin
where the SPC lesion had prominent signet-ring cell features. In conclusion, SPCs are
heterogeneous lesions that arise in older women and have an indolent behavior.
Lymph node and distant metastases are uncommon and generally limited to cases with
(conventional) invasive components
Clearly identifying invasive papillary carcinoma can be difficult in some cases.
Entrapped papillary or glandular clusters of epithelial cells found in sclerotic areas
with evidence of prior hemorrhage represent a diagnostic problem. Because the same
pattern of pseudoinvasion occurs in sclerotic portions of benign papillary lesions,
these foci are not evidence of invasion. The best evidence of invasion is clear-cut
extension of tumor into stroma beyond the zone of reactive changes. Invasive
micropapillary carcinoma is defined by the presence of myriads of small solid or
tubular neoplastic cell groups lying within individual connective tissue “cells” formed
from a spongiform-appearing desmoplastic collagenous matrix. Neoplastic cells
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