Table 3.

Colon cancer: reason for incorrect identification of cases and non-cases

Invasive colon cancer
Type of misclassification	Umbria	ASL Napoli 3 Sud	Friuli Venezia Giulia
False positives
1 Missing histological examination	13*	15†	11‡
2 Possible negative histology	12§	8¶	15**
a) Adenoma (from biopsy specimen)	2	3	7
b) Adenoma (from surgical specimen)	7	1	4
c) Negative	3	3	3
d) Adenocarcinoma in situ	–	1	1
Total	25	23	26
False negatives
1 Possible colon cancer relapse	1	–	–
2 Metastatic colon cancer	–	2	–
3 Unclear/histological exam missing	–	–	2
Total	1	2	2

*Metastatic lesions from instrumental exam (n=3); positive for colon adenocarcinoma from histological documentation in a subsequent admission (n=3); positive for rectal adenocarcinoma from histological documentation in a subsequent admission (n=1); deceased (n=1).

†Metastatic lesions from instrumental exam (n=4); chemotherapy or radiotherapy (n=1); previous colon cancer diagnosis (n=1); biopsy not performed (patient with cachexia) (n=1); positive for colon adenocarcinoma from histological documentation in a subsequent admission (n=4).

‡Positive for colon adenocarcinoma from histological documentation in a subsequent admission (n=6); metastatic lesions from instrumental exam (n=1).

§Histological documentation missing for the second lesion (n=4).

¶Histological documentation missing for the second lesion (n=5); positive for colon adenocarcinoma from histological documentation in a subsequent admission (n=1); metastatic lesions from instrumental exam (n=2).

**Metastatic lesions from instrumental exam (n=1); positive for colon adenocarcinoma from histological documentation in a subsequent admission (n=7); positive for rectal adenocarcinoma from histological documentation in a subsequent admission (n=2).