Answer to Quiz No. 76 dated 21 August 2016
Pleomorphic adenoma - right parotid gland
Findings
A well-defined and lobulated heterogenous mass lesion is seen involving the superficial and deep lobes of the right parotid gland. The mass lesion show mixed signal intensity on T2-weighted images. Areas of hemorrhage is seen within the mass peripherally. No extension of the mass outside the parotid gland is seen. no significant enhancement seen. the mass is seen extending across the facial nerve plane within the parotid. no significant vascularity is seen within the mass. Left parotid gland is normal.
Discussion
The imaging of a pleomorphic adenoma shows the typical picture of a benign-appearing mass. On sialography, pleomorphic adenoma displaces the parotid ducts smoothly around the tumor mass. On CT, most small benign mixed tumors are smoothly marginated, spherical tumors that have a higher attenuation than the surrounding parotid parenchyma. There is a strong tendency for these tumors to have a lobulated contour. On occasion, these tumors can have a lower attenuation than the surrounding parotid parenchyma and mimic the appearance of a cyst. Most of these lower attenuation tumors are primarily mucoid in nature. All of these tumors enhance variably on contrast-enhanced studies. The smaller lesions are usually fairly homogeneous in appearance. If delayed contrast-enhanced CT scanning is not performed in these cases, the mass may be overlooked. The larger masses most often have a nonhomogeneous appearance, with sites of lower attenuation representing areas of necrosis, old hemorrhage, and cystic change. Localized areas of increased attenuation most often represent sites of recent hemorrhage and are associated clinically with a sudden increase in tumor size and localized pain. As mentioned, these tumors, especially when large tend to develop a lobulated contour that, when present, is highly suggestive of the diagnosis. Such a lobulated mass on CT may appear as multiple adjacent masses rather than a solitary lesion; however, on MR imaging they are clearly seen as a solitary mass. On MR imaging, these tumors typically have a low T1-weighted and a high T2-weighted signal intensity. A low-signal-intensity “capsule” is often seen on T2-weighted scans and on fat-suppressed, contrast-enhanced, T1-weighted images. Dystrophic calcifications or ossifications can occasionally be seen scattered throughout the tumor.
References
Som and curtin. head and neck textbook of radiology
Findings
A well-defined and lobulated heterogenous mass lesion is seen involving the superficial and deep lobes of the right parotid gland. The mass lesion show mixed signal intensity on T2-weighted images. Areas of hemorrhage is seen within the mass peripherally. No extension of the mass outside the parotid gland is seen. no significant enhancement seen. the mass is seen extending across the facial nerve plane within the parotid. no significant vascularity is seen within the mass. Left parotid gland is normal.
Discussion
The imaging of a pleomorphic adenoma shows the typical picture of a benign-appearing mass. On sialography, pleomorphic adenoma displaces the parotid ducts smoothly around the tumor mass. On CT, most small benign mixed tumors are smoothly marginated, spherical tumors that have a higher attenuation than the surrounding parotid parenchyma. There is a strong tendency for these tumors to have a lobulated contour. On occasion, these tumors can have a lower attenuation than the surrounding parotid parenchyma and mimic the appearance of a cyst. Most of these lower attenuation tumors are primarily mucoid in nature. All of these tumors enhance variably on contrast-enhanced studies. The smaller lesions are usually fairly homogeneous in appearance. If delayed contrast-enhanced CT scanning is not performed in these cases, the mass may be overlooked. The larger masses most often have a nonhomogeneous appearance, with sites of lower attenuation representing areas of necrosis, old hemorrhage, and cystic change. Localized areas of increased attenuation most often represent sites of recent hemorrhage and are associated clinically with a sudden increase in tumor size and localized pain. As mentioned, these tumors, especially when large tend to develop a lobulated contour that, when present, is highly suggestive of the diagnosis. Such a lobulated mass on CT may appear as multiple adjacent masses rather than a solitary lesion; however, on MR imaging they are clearly seen as a solitary mass. On MR imaging, these tumors typically have a low T1-weighted and a high T2-weighted signal intensity. A low-signal-intensity “capsule” is often seen on T2-weighted scans and on fat-suppressed, contrast-enhanced, T1-weighted images. Dystrophic calcifications or ossifications can occasionally be seen scattered throughout the tumor.
References
Som and curtin. head and neck textbook of radiology
