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Among the most frequently referred samples to SESC are the granulomatous lesions to rule out tuberculosis. On this occasion we will test your laboratory skills as we show you a special histological staining, would you be able to recognize which technique it is and what are the blue structures that can be observed? (EV)

Lesió granulomatosa al nòdul limfàtic mediastínic caudal d'un vedell de12 mesos de raça creuada.

Mineralized granulomatous lesion in the caudal mediastinal lymph node of a 12-month-old cross-bred calf. The animal had a similar lesion in the lung parenchyma.

Tinció especial que mostra la presència d'estructures de color blau tenyides a l'interior de les cèl·lules inflamatòries.

Special staining showing the presence of blue structures stained inside some inflammatory cells. Notice that multinucleated giant cells are observed.

Un altre fragment del granuloma on les estructures blavoses allargades son força abundants.

Another fragment of the granuloma where the elongated bluish structures are quite abundant.

What is your diagnosis? (97)

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The histopathological study showed lesions of necrotizing granulomatous lymphadenitis, with abundant multinucleated giant cells. The staining we show you corresponds to a Gram stain that evidences filamentous gram-positive bacilli, predominant in the non-necrotic areas of the lesion. Microbiological culture allowed to isolate Nocardia spp. from this lesion. The histological diagnosis of tuberculosis-compatible macroscopic lesions allows to quickly rule out a TB suspicion, thus maintaing the TB-free status of the herd.

Your answers are highlighted below.
Question 1
Which staining it is and what are the blue-stained structures?
A
Grocott stain - Fungal hyphae
B
Ziehl Neelsen stain - Mycobacterium spp bacili
C
Gram stain - Corynebacterium pseudotuberculosis bacili
D
Gram stain - Nocardia spp. filamentous bacili
E
PAS stain - Fungal hyphae
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