It is common in our practice as dermatopathologists to receive specimens with a differential diagnosis of sarcoidosis vs. tuberculoid leprosy for histopathological verification. Interestingly enough, on mere morphological basis, one might be unable to differentiate between these two conditions.

Both present with non caseating granulomas. Whereas, sarcoidosis is typically characterized by discrete uniform naked granulomas, tuberculoid leprosy granulomas tend to be oval and surrounded with dense lymphocytic infiltrate and are usually seen around nerves. However, as usual in dermatopathology, diseases do not follow exactly textbooks. Granulomas in sarcoidosis may be lymphocyte rich, may be oval in shape and may be seen around nerves making differentiation from tuberculoid leprosy difficult.

In such conditions, morphological clues of sarcoidosis include the discrete uniform nature of the granulomas, the presence of foci of fibrinoid necrosis and the presence of perigranulomatous fibrosis. Although, granulomas in sarcoidosis may surround nerves, this is not associated with evident nerve destruction which is typical of tuberculoid leprosy. Confirmation of nerve destruction sometimes requires work up with S100, EMA or silver stains. Detection of lepra bacilli by Fite stain will confirm a diagnosis of tuberculoid leprosy, but sometimes this stain is not available and in some cases of tuberculoid leprosy the organisms are so sparse and may not be found in skin lesions.

Accordingly, it is the constellation of all the findings of the clinical picture, the histopathological morphology and the auxiliary work up that will finalize the diagnosis.