A case of Bacille Calmette-Guérin (BCG) lymphadenitis

Clinical History

A 2-year-old immunocompetent female patient, BCG vaccinated at birth, was transferred from another unit for surgical evaluation of a persistent soft mobile painless left axillary mass. Previous imaging and aspiration were not suggestive of malignancy or granulomatous disease. There was significant parental anxiety. Surgical excision was performed.

Imaging Findings

The initial ultrasound images were not available, but a second sonographic examination was performed following transfer, with an 11 MHz linear transducer.
In the left axilla a hypoechogenic and homogeneous solid nodule was detected, measuring 34 x 14 x 18 mm. An echogenic peripheral band was found, as well as a few echogenic speckles randomly distributed within the lesion. No vascularity or cystic component was detected.

Discussion

Bacille Calmette-Guérin (BCG) vaccine contains live attenuated Mycobacterium bovis and was incorporated into the World Health Organization Expanded Program on Immunization in 1974 to prevent tuberculosis. BCG vaccine leads to a self-limited primary complex, with a cutaneous nodule at the site of injection and subclinical involvement of regional lymph nodes, requiring no treatment.
The most common complication of BCG vaccination is lymphadenitis, which is diagnosed based on the clinical finding of isolated ipsilateral lymph node enlargement, likely with a diameter equal or greater than 1 cm, after vaccination, without any other identifiable cause. It tends to develop 2 weeks to 6 months post immunization, but can appear within 24 months, and usually affects axillary lymph nodes, although supraclavicular and cervical lymph nodes can also be involved [1].
In the majority of cases, BCG lymphadenitis develops into a non-suppurative form, which usually regresses spontaneously over a period of a few weeks. It requires close observation and follow up. Antibacterial treatment is not recommended but, if the node remains persistently enlarged, with a diameter larger than 3 cm for 6-9 months, surgical excision may be performed. In some cases, the affected lymph node may enlarge and develop suppuration, suggested by the identification of fluctuation in the swelling with oedema and erythema of the skin. Suppurative lymphadenitis may also develop abruptly within 2-4 months of immunization. In this situation, needle aspiration is recommended. Upon failure of aspiration, surgical excision is indicated [2].
Immunocompromised individuals may develop disseminated BCG infection, with a poor prognosis.
Descriptions of the sonographic features of BCG lymphadenitis are scarce. One study describes variable features, but, in a high proportion of subjects, axillary lymph nodes with multiple internal echogenic speckles were encountered, and this may be regarded as a sonographic feature of this condition [3].

Differential Diagnosis List

Final Diagnosis

Bacille Calmette-Guérin lymphadenitis

URL:	https://eurorad.org/case/14659
DOI:	10.1594/EURORAD/CASE.14659
ISSN:	1563-4086