Detection of mycobacterial infections using the Dieterle stain

The morphological spectrum of lymphadenopathy in HIV infected patients

AIMS

To study the histological spectrum of lymphadenopathy in human immunodeficiency virus (HIV) infected Thai patients.

METHODS

Lymph nodes from 55 HIV infected patients were accessioned over a 19 month period in two pathology laboratories in Bangkok, Thailand. These were examined with H&E, Ziehl-Neelsen, periodic acid-Schiff (PAS), PAS with diastase (PAS/D), Gram and methenamine stains.

RESULTS

Six reaction patterns were observed: (1) classic necrotising granulomas (30 cases); (2) extensive necrosis with minimal granulomatous response (5 cases); (3) sarcoid-like non-necrotising granulomas (5 cases); (4) foamy macrophage or pseudo-Gaucher cell response (5 cases); (5) inflammatory pseudotumour-like proliferation (3 cases); and (6) non-specific lymphoid hyperplasia (7 cases). Myriads of intracellular, long, slender acid-fast bacilli were found in those cases with the pseudo-Gaucher cell and inflammatory pseudotumour-like response, while variable numbers of bacilli were identified in those cases with non-necrotising sarcoid-like granulomas. Few scattered acid-fast bacilli were found in five cases with necrotising granulomas. In one case, yeast-like organisms in keeping with Cryptococcus were identified. No organisms were identified in the cases showing lymphoid hyperplasia, extensive necrosis and minimal granulomatous response, and in the remaining cases of classic necrotising granulomas.

CONCLUSIONS

The wide spectrum of histological changes in HIV-associated lymphadenomegaly requires recognition, particularly as the majority were associated with acid-fast organisms, mostly in keeping with the morphological features of Mycobacterium avium-M. intracellulare complex that was distinctively stained by Grocott methenamine-silver, Gram and PAS stains. The histological changes mimic those of infarction and other infective lymphadenitis, sarcoidosis, Whipple's disease, inflammatory pseudotumour and spindle cell neoplasms.

Atypical mycobacterial lymphadenitis in childhood--a clinicopathological study of 17 cases

AIMS

To assess the clinical and pathological features of atypical mycobacterial lymphadenitis in childhood to define the salient clinical and histological features.

METHODS

17 cases were included on the basis of positive culture or demonstration of bacilli of appropriate morphology and staining characteristics.

RESULTS

The mean age at diagnosis was 4.86 years. All children were systemically well, with clear chest x rays. Unilateral cervical lymphadenopathy was the commonest mode of presentation. Differential Mantoux testing played no part in diagnosis. Clinical diagnosis improved with awareness. Treatment varied with surgeons opting for excision and paediatricians adding six months antituberculous chemotherapy. Acid- and alcohol-fast bacilli were identified in nine cases. Bacterial cultures were conducted in 16 cases and were positive for atypical or nontuberculous mycobacteria in 14, the main organism being M avium-intracellulare complex (11 cases). Histologically, 12 cases had bright eosinophilic serpiginous necrosis with nuclear debris scattered throughout the necrotic foci. Langhans type giant cells featured in the majority of cases but infiltration by plasma cells and neutrophils was not consistent.

CONCLUSIONS

Atypical mycobacterial lymphadenitis of childhood represents a rare but significant disease with characteristic clinical and histological features.