Italian to English Medical Medical (general)

I am translating medical reports related to a biopsy performed for a possible adenocarcinoma of the cardia.

There is an acronym I cannot understand "fs"... here is some context:

"Descrizione macroscopica:
1. Frammento di tessuto grigiastro di 0.8 cm
1 fs in toto per esame al congelatore

Prelievi:
1fs: non evidenza di neoplasia sulle sezioni in esame "

Can anyone tell me what "1 fs" or "fs" stands for?

Thank you in advance
Alice