Medical news: Rare Medical condition of the parotid gland

Castleman's disease, a rare benign lymphoproliferative disorder, may be localized or widespread, with the localized form having two histopathological types. The hyaline vascular type is seen in the majority of cases, commonly presenting with only pressure symptoms in young individuals.

Parotid Castleman's disease is extremely rare. To the best of the authors' knowledge, fewer than 20 cases have been reported in world literature so far. There has been only one previous case report describing the ultrasonographic findings in parotid Castleman's disease, described in a 50-year-old man in whom ultrasound showed an ill-defined, heterogeneous, partly cystic mass with multiple intraparotid and cervical lymph nodes. 

Ultrasound image of Castleman's disease
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In the present case, ultrasound showed a more homogeneously hypoechoeic mass with surrounding hypoechoeic intraparotid and cervical lymph nodes. The findings are more consistent with the sonographic findings described in Castleman's disease affecting other sites.

The ultrasonographic findings are, however, not specific and may even be seen in lymphoma. However, the Doppler examination showed an exuberant vascular pattern with prominent peripheral vessels and penetrating feeding vessels entering the hilum, which is suggestive of Castleman's disease. Colour Doppler and spectral analysis have been found to be useful in differentiating the different lymphadenopathies. Benign lymph nodes are, by and large, avascular or show a hilar vascularity without peripheral flow, whereas in metastatic lymphadenopathy a spotted, peripheral or mixed pattern of vascularity is noted. However, the vascular patterns are not entirely specific. Benign causes, such as Kikuchi's disease, have been shown to depict an abnormal vascularity. 
Moreover, malignant conditions such as lymphoma, especially in the early stages, can depict a benign pattern of flow. Hence, spectral analysis is usually used to add to the specificity. Malignant lymph nodes usually depict a high resisitivity and pulsatility index (RI and PI, respectively) with a cut-off for the RI of more than 0.8 and for the PI of more than 1.5, increasing the specificity. The Doppler findings in parotid Castleman's disease have not been previously described in the literature. In our case, the spectral wave pattern showed a low-resistance arterial flow (RI of 0.59), which favours a benign aetiology, although the vascular pattern was of the mixed type with prominent peripheral as well as hilar flow.

Although imaging features can indicate the diagnosis, histopathological confirmation is usually required. Histopathological examination in this case showed germinal centres within follicles with interfollicular capillary proliferation showing hyalinization, suggestive of the hyaline vascular type of Castleman's disease.

To conclude, parotid Castleman's disease is a rare entity. Being superficial, it is readily assessed using ultrasound. The findings of a uniformly hypoechoeic mass showing exuberant peripheral vascularity with prominent penetrating hilar vessels and surrounding lymphadenopathy should indicate the diagnosis.

Further research article here