Ultrasound and MR Appearance of Lymph Nodes

Normal lymph nodes are usually ovoid in shape, with a fatty hilum and an organized vascular pattern radiating from the hilum57 (Fig. 4.14). Some features, such as focal areas of necrosis, are highly specific for malignancy, and in general malignant nodes tend toward roundness and may lose their fatty hilum58 (Fig. 4.15). One recent study of the use of ultrasound in 44 patients, the majority of whom had penile cancer, showed that in 42/44 patients with metastasis at least one of the following features suggestive of malignancy was present: long/short axis ratio < 2, absent hilum, wide cortex, or eccentric cortical widening. The problem with this study is that although the individual criteria had acceptable specificity, and each had a positive predictive value >78%, many reactive nodes also showed at least one malignant feature.59 Others emphasize that the presence of a normal fatty hilum cannot be used to exclude malignancy.6 0 A further set of criteria based on Resistive index and Pulsatility index have been proposed, with one author finding that cutoffs of RI > 0.8 and PI > 1.6 had a sensitivity (specificity) of 80% (94%) and 94% (97)%, respectively, in the four fifths of neck nodes that had detectable flow.61 Whether such results could be replicated in penile squamous carcinoma is, however, uncertain, and Doppler studies can be challenging: morphology and size are the mainstay of diagnosis.

Liquefaction Lymph Node Ultrasound

Fig. 4.14 (a-c) Features of a benign lymph node (arrowheads) on ultrasound, doppler ultrasound, and MRI respectively. Note the fatty hila in each case (white arrow). The ultrasound shows ovoid nodes with a regular cortex of uniform thickness; on doppler (b), small vessels radiate symmetrically from the hilum (small white arrows). MRI (c) shows nodes in short axis: approximately round, but with fatty hila and regular cortex

Inguinal Lymph Nodes Mri

What of size criteria? As benign nodes enlarge, they preserve their ovoid shape, if the ratio of long to short axis diameters remained >2, the negative predictive value in two series was 81-87%.5 9,62 Because malignant nodes tend to be more circular, enlargement of the short axis is often used for detecting them: one study of vulval

Totally Necrotic Lymph Node Ultrasound

Fig. 4.15 Several features of malignant nodes. (a) Ultrasound shows an enlarged node with eccentric, lobulated enlargement of the cortex (arrowheads show the hilum, and the arrows the eccentric widening), and (b) a doppler trace of the same node showing a resistive index of 1.2. (c-f) Malignant nodes (arrowheads) with necrosis on ultrasound, CT, T2-weighted MRI, and postcon-trast MRI (in different patients). The necrotic focus (white arrow, (c)) is nearly anechoic on ultrasound. On CT (d) it is of low density (close to water). (e) A node consisting of an eccentric nodule (black arrow) and fluid necrosis (white arrow) on a T2-weighted axial MR sequence. (f) A post-contrast gradient echo fat-saturated coronal sequence of the same node showing the nonenhancing necrotic component

Fig. 4.15 Several features of malignant nodes. (a) Ultrasound shows an enlarged node with eccentric, lobulated enlargement of the cortex (arrowheads show the hilum, and the arrows the eccentric widening), and (b) a doppler trace of the same node showing a resistive index of 1.2. (c-f) Malignant nodes (arrowheads) with necrosis on ultrasound, CT, T2-weighted MRI, and postcon-trast MRI (in different patients). The necrotic focus (white arrow, (c)) is nearly anechoic on ultrasound. On CT (d) it is of low density (close to water). (e) A node consisting of an eccentric nodule (black arrow) and fluid necrosis (white arrow) on a T2-weighted axial MR sequence. (f) A post-contrast gradient echo fat-saturated coronal sequence of the same node showing the nonenhancing necrotic component

Fig. 4.15 (continued)

Penile Cancer ImagesMedicine Penile Mass Benign

nodes (studies purely of penile cancer are sparse) found that a short axis of 8 mm diameter or more had a sensitivity of 83% for the detection of malignancy.63 However, this was a small group of patients and overall there is great overlap in short axis size between malignant and benign nodes in the groin.64,65 Sohaib et al. achieved a sensitivity and specificity of 40% and 97% using 10 mm for superficial nodes, and 50% and 100% using 8 mm for deep inguinal nodes,66 while others have achieved better results (sensitivity of 87%, specificity 81%) for a morphological criterion of short/ long axis ratio >0.75. The fundamental limits to the technique are that (1) a small degree of infiltration will not significantly affect the size of a node and (2) reactive nodal enlargement from local inflammation is particularly common in cancer of the penis, and the cause of nodal enlargement in 25-50% of palpable groin nodes at presentation,1,67 though palpable nodes at follow-up are almost always malignant.68

In the pelvis studies of genitourinary cancers which have primarily used size criteria (usually conducted with CT and MRI) have shown sensitivity ranging from 6% to 78% for malignancy, with specificity 65% to 98%, depending on the cancer studied and the size criterion used.39,70 The commonest size criterion for pelvic nodes (usually based on studies of commoner cancers such as prostate and cervix) is 10 mm in short axis,14,70 though others advocate 8 mm if the node is round71; there are no large studies specifically of penile cancer in the pelvis.

Although signal intensity is a poor discriminator in inguinal72 and pelvic nodes (including with contrast enhancement),14 necrosis (Fig. 4.15) in a pelvic node (indicated by a component showing signal characteristics of fluid) is a highly suggestive

Fig. 4.16 Positive lymph nodes on PET. (a) Two nodes (large arrows) in the right groin are suspicious by morphology and size criteria (though they could also be reactive). (b) On PET they show markedly increased uptake and were positive at histology. Several smaller nodes in the left groin were negative on PET (small arrows) and at histology. Pelvic nodes were negative at PET and histology after pelvic nodal dissection

Ultrasound Abnormal Lymph Node Groin

' Jllj^l finding,7 and in head and neck squamous cancers at least is a reliable indicator of malignancy.73 Although often occurring in larger nodes, it can also be seen in those <1.5 cm; on MRI as a focus of fluid signal, on CT as a low density focus and on ultrasound as a hypo or hyperechoic focus, or one that shows fluid movement with pressure from the probe.73 For this assessment MRI and CT are likely comparable, with ultrasound inferior (especially in the pelvis, where views are poor).73

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Responses

  • philipp
    What is the white in a lymph node from ultrasound?
    2 years ago
  • kirsi
    Are normal lymph nodes detectable in ultrasound?
    1 year ago
  • samppa
    How often susspicios lymph nodes on ultrasound turn to be malignant?
    3 months ago
  • alexander
    Why would a lymph node appear black on ultrasound?
    25 days ago

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