Histologic Changes

The wedge resection measured 4 x 3 x 3 cm. Focal necrosis was noted in a nodular mass.

Each of the following pictures was taken from sections of the mass. Examine them and give a description of each. Then formulate the differential diagnosis.

Descriptions and differential diagnosis

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Descriptions

At low power, nodular collections of confluent granulomas are surrounded by dark blue lymphoid cells. Note the small, rounded granulomas at the edge of the central nodule. At the center of the confluent granulomas is a pink zone of necrosis.

The individual, rounded granulomas are composed of activated, epithelioid histiocytes with abundant cytoplasm, multinucleated giant cells, which represent fused epithelioid cells, and lymphocytes.

At the edge of the necrotic zone are lymphocytes, epithelioid cells, and multinucleated giant cells but no well-formed granulomas.

Note the two types of multinucleated giant cells: the Langhans' cell with nuclei at the edge and the foreign body type giant cell with nuclei scattered throughout the cytoplasm.

Differential diagnosis: The differential diagnosis includes mycobacterial or fungal granulomas, and special stains for organisms were performed. No fungi were found. Most fungi, with the exception of Pneumocystis carinii, can be seen with ordinary H&E stains. The Gomori methenamine silver stain is performed, nevertheless, to find rare organisms and to help identify them. In this particular biopsy, two acid-fast organisms were found on the Ziehl-Neelsen stain. As in most immunocompetent hosts, the organisms were found in the necrotic areas and not in the cellular rim. Three weeks later, the culture of the tissue was positive for M. tuberculosis.

Non-infectious diseases in the differential diagnosis include Wegener's granulomatosis and nodular sarcoidosis.

This Ziehl-Neelsen-stained section from another case shows many acid-fast tubercle bacilli that are associated with cells undergoing lysis.

 

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