Case: AP94
Contributor's Comment: In this case, plenty acid fast bacilli are present in the spindle cells and vacuolated cells. Besides ZN, the bacilli are also positive for Grocott and PASD, suggesting that they are atypical mycobacteria. Culture also confirmed that they were not MTB. Inflammatory pseudotumour is an acceptable diagnosis. However, one must exclude specific infection (and inflammatory variants of neoplasms) before one commits to such a descriptive diagnosis. Obviously the management and clinical course will be different. In fact, greyish granular material can be detected in the vacuolated histiocytic cells on careful high-power examination of the H&E stained section, and is a clue that the lesion may be secondary to an infectious etiology.
Marks are given according to the % allocated to those who returned a diagnosis of inflammatory/infective lesion, and up to 30 marks are added to those who mentioned special stains for microorganisms in the comment. But 10 points are deducted from those (109,123,259,448) who have not specifically included ZN stain or seriously considered the possibility of infection. (MST)