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

medullary carcinoma, when compared to matched patients with grade 3 InvDC,NST.
Clinicopathologic features: The mean age at presentation in several series has ranged
from 46 to 54 years (10,16,16). Medullary carcinomas have circumscribed margins, a
soft to moderately firm consistency, and are often mistaken for fibroadenomas,
especially in young women. Bilateral carcinomas and multicentricity may occur
(3,11,16,17).
(“Multicentricity” is defined here as microscopic foci of carcinoma outside the
primary quadrant, and it implies the presence of multiple clonally distinct tumors.
Synchronous multicentric tumors are uncommon in my experience. “Multifocal”
tumors are much more common, and “multifocal” refers to separate, satellite foci of
one invasive tumor clone. This feature is often observed in invasive lobular
carcinoma. It likely results from “skip” invasive tumor, resulting from lymphaticvascular
spread and/or relatively synchronous invasion from multiple separate points
along the breast duct system by one carcinoma clone that has previously spread
through the breast along the duct system.)
In patients with medullary carcinoma, ipsilateral axillary lymph nodes are often
enlarged, even when there are no nodal metastases, due to reactive lymphoid and
histiocytic hyperplasia. The median size of the primary tumors is 2 to 3 cm. Peripheral
fibrosis may suggest encapsulation, and some small tumors appear less well
circumscribed due to an intense lymphoplasmacytic reaction that extends into adjacent
breast tissue (10). InvDC,NST may also be well-circumscribed. Cut surfaces reveal a
round or lobulated, pale brown to grey tumor, which is softer than the usual breast
carcinoma. Hemorrhage, necrosis, and cystic changes may be present, especially in
larger lesions.
Those who believe medullary carcinoma is a tumor with a favorable prognosis agree
that it is necessary to adhere to strict morphologic criteria for the diagnosis
(3,11,10,18). As described by Foote and Stewart (19), the definitive features must
include 1) a prominent lymphoplasmacytic reaction, 2) circumscription, 3) a syncytial
growth pattern (i.e., broad anastomosing sheets of tumor cells with indistinct cell
borders), 4) poorly differentiated nuclear grade, and 5) high mitotic rate. The
lymphoplasmacytic reaction must be intense enough to be "graded" at least as
“intermediate” or “moderate” in amount (i.e., the mononuclear infiltrate involves at
least 75% of the periphery and is present diffusely in the substance of the tumor).
According to Rosen et al. (15) the lymphoplasmacytic reaction commonly encompasses
ducts and lobules in the surrounding breast occupied by carcinoma in situ
as well as nearby benign ducts and lobules not containing carcinoma. He believes
expansile growth of in situ carcinoma in ducts and lobules leads to the formation of
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