LIBRO DE OBSEQUIO SORPRESA 1 BREAST CANCER

14
Histological Diagnosis of Implant-Associated Pathologies
j3: ≥50 CD15 + PMN in a Single Focal Point of 1 HPF (CD15 Focus Score)
The CD15 focus score is a simple counting algorithm for PMN. This method counts
CD15 + cells in a single focal point, independent of location, and is based on a specific
property of PMN (CD15 expression). Ultimately, this score follows the principle of maximum
severity (grading of the worst area), a well-established principle in histological diagnosis
that also takes into account the focal nature of the inflammatory infiltrate in the
periprosthetic tissue [30].
The PMN count is performed using a ×20 lens magnification in an area or a field size
of about 0.26 mm 2 (. Fig. 12). With a value of ≥50 CD15 PMN/focal point, in 1 HPF, a
bacterial infection can be diagnosed with a sensitivity of 87% and a specificity of 90% [30].
These data validate the CD15 focus score as a method for the histological diagnosis of
implant infection and its accuracy is increased by the use of a CD15 quantification software,
such as the CD15 Quantifier, VMscope (Berlin, Germany) [30]. Although the quantification
of the PMN content remains the gold standard for the histological diagnosis of
infection, adjuvant criteria are the loss of lining cell layer, edema, and formation of granulation
tissue. In particular, modifications in the structure of the neo-synovial membrane
are important in cases of low-grade infection, in which the differential diagnosis with
untreated or therapy-resistant inflammatory synovitis of rheumatic disorders in the active
phase can also be a challenge, especially on arthroscopic shavings or with limited tissue
sampling for frozen section. Usually the presence of hyperplasia of the cell lining layer and
of lymphoplasmacytic infiltrate is useful in addressing the correct diagnosis, even when the
threshold of the PMN count for low-grade infection is met.
. . Fig. 12 CD15 focus score in infection-induced SLIM (type II). Case of total hip arthroplasty high-grade infection
with positive E. coli culture and a CD15 focus score of 485. The cells with a blue border represent polymorphonuclear
leukocyte (CD15 quantifier mode, field size about 0.26 mm 2 )