Juxtapleural lung nodules

Juxtapleural nodules (JPNs) are classified by their location subjacent or close towithin 15mm of a pleural surface. Intraparenchymal lymph nodes are typically subpleural or juxtapleural in location ⁷ but must be distinguished from small peripheral cancers ⁸.

Terminology 

The term perifissural nodule is outdated and ignores lymph nodes located adjacent to the costal, mediastinal and diaphragmatic pleura.

Radiographic features

CT

Intraparenchymal lymph nodes are characteristically homogeneous, soft tissue attenuation, well-defined nodules with a smooth outline and a lentiform, ovoid, semicircular, triangular or polygonal shape, located on or within 10 mm15mm of the visceral pleura ⁹. They can be contiguous with the pleura or they can lie at the junction of interlobular septa in which case the septala thin linear attachment to the pleural surface is often visible ³. They are predominantly located inferior to the carina in the middle or lower lobes.

Features that are not typical for lymph nodes include ⁶: 

• upper zone location

• spherical shape

• any surface irregularity e.g. indistinct, spiculated, microlobulated

• pleural distortion e.g. bowing, retraction, thickening, transgression (fissure)

• size > 1012 mm should be followed-up

• not completely solid ⁸

• intranodular fat or calcification

Peripheral cancers are most commonly adenocarcinomas, followed by squamous carcinomas and carcinoid tumours. These are commonly round in shape. Carcinoids may have a smooth regular margin, but other tumours characteristically demonstrate surface irregularity and are less sharply marginated. Spiculation and microlobulation are the more obvious signs of malignancy. Signs of visceral pleural invasion may also be present ¹⁰:

• jellyfish sign (pleural-adjacent nodule with multiple pleural tags arising from superior/inferior partthe margins of the nodule)

• pleural thickening

• large contact surface area for pleural-adjacent nodules

• multiple tags to different pleural surfaces

Treatment and prognosis

If JPNs have all the typical features of intraparenchymal lymph nodes they are likely to be benign and follow-up at 1 year may be appropriate, however lymph node size can change over time and they may demonstrate interval growth over serial scansgrow ² or shrink over time.

Caution is advised due to observerfor upper lobe nodules. Observer variation is well-documented, particularly so with radiologists inexperienced in this area.