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Objective: Our aim was to describe the MRI findings of subcutaneous epidermal cysts with an emphasis on determining the presence of rupture., Conclusion: Epidermal cysts show a fluidlike signal with variable low-signal components on T2-weighted images and peripheral rim enhancement on gadolinium-enhanced images. Most ruptured cysts have septa, show thick and irregular rim enhancement, and are accompanied by a fuzzy enhancement in surrounding subcutaneous tissues. These imaging features of a ruptured epidermal cyst simulate a mass of infectious or neoplastic origin.

Objective: This study was performed to identify the typical imaging features of steatocystoma multiplex on mammography and sonography., Conclusion: Steatocystoma multiplex is manifest by multiple clinically palpable skin-colored or yellow nodules scattered on the axillae and the anterior chest wall. Steatocystoma multiplex is included in the differential diagnoses of lipoma, fat necrosis, galactocele, epidermal cyst, and so on, so radiologists need to be aware of its distinguishing features. The findings of a well-circumscribed round fat-density nodule on mammography or an intradermal hypoechoic nodule on sonography, combined with a family history of steatocystoma multiplex (40%) and an extensive bilateral spatial distribution of nodules, confirm the diagnosis of steatocystoma multiplex.

Objective: The purpose of this study is to analyze the sonographic and MR imaging findings of testicular epidermoid cysts., Conclusion: Sonographic findings of a markedly heterogeneous intratesticular mass with or without alternating hypo- and hyperechoic layers surrounded by a hypoechoic or echogenic rim and the absence of flow on color Doppler sonography suggest the preoperative diagnosis of testicular epidermoid cysts. T2-weighted MR imaging findings of a high-signal-intensity mass with or without low-signal-intensity foci surrounded by a low-signal-intensity rim and the absence of enhancement on contrast-enhanced T1-weighted MR images can strengthen the preoperative diagnosis. These imaging findings can offer a basis for surgeons to attempt testis-sparing surgery instead of orchiectomy.

Objective: The purpose of this study is to analyze the appearance of testicular epidermoid cysts on high-resolution sonography and MR imaging and correlate imaging features with histopathologic findings., Conclusion: Intratesticular epidermoid cysts may show imaging features that correlate with their histopathologic findings. Concentric rings of alternating hypo- and hyperechogenicity on sonography and alternating high and low signal intensity on MR imaging ("onion ring" appearance) correspond to the pathologic finding of multiple layers of keratin debris. Absence of flow on color Doppler sonography and absence of contrast enhancement on MR imaging is also consistent with the avascular nature of these lesions. The ability of preoperative imaging studies to suggest the diagnosis of epidermoid cyst may prompt a testis-sparing surgery instead of an orchiectomy.

Objective: We categorized the MR imaging characteristics of intracranial epidermoid tumors., Materials and Methods: MR images from 23 cases of intracranial epidermoid tumors were reviewed retrospectively. Signal intensities of tumor relative to surrounding structures were noted, as were the internal architecture of the tumors and the presence and degree of hydrocephalus., Results: Seventeen (74%) of 23 cases of intracranial epidermoid tumors were revealed as slightly hyperintense relative to CSF on T1-weighted MR images. Nineteen (95%) of 20 cases were hyperintense relative to CSF on proton density-weighted MR images. Fifteen (65%) of 23 cases were isointense to CSF on T2-weighted MR images, whereas the remaining eight cases (35%) were hyperintense to CSF on T2-weighted MR images. One (4%) of 23 cases showed signal intensity that was isointense to CSF on all pulse sequences. Fifteen (65%) of 23 cases showed heterogeneous signal characteristics on either T1-weighted or proton density-weighted MR images, or both. Eight (35%) of 23 cases showed a rim of hyperintensity on proton density-weighted MR images. Five (33%) of the 15 cases that received gadolinium showed rim enhancement. Five (22%) of 23 cases were multilocular, with different regions of tumors showing highly variable imaging characteristics. Two (9%) of 23 cases showed high signal intensity on T2-weighted MR images in the adjacent brain parenchyma. Two (9%) of 23 cases showed mild hydrocephalus. Six (43%) of 14 tumors that either originated in or secondarily involved the cerebellopontine angle also extended into the ipsilateral Meckel's cave., Conclusion: On T1-, proton density-, and T2-weighted MR images intracranial epidermoid tumors usually showed heterogeneous signal intensity that was hyperintense to CSF. On all spin-echo pulse sequences epidermoid tumors with signal characteristics isointense to CSF were unusual. Hydrocephalus, even in the setting of marked displacement and compression of the brainstem, was not usually seen on MR imaging. Meckel's cave was often involved secondarily with epidermoid tumors that involved the cerebellopontine angle.

Objective: This study evaluated the effectiveness of steady-state free-precession (SSFP) MR imaging of complex cystic masses of the brain compared with that of conventional T1- and T2-weighted spin-echo imaging. Our hypothesis is that SSFP MR images provide better characterization of these masses and facilitate more appropriate preoperative diagnoses and planning., Subject and Methods: Axial T1-weighted and SSFP MR images and specimens for pathologic examination were obtained in seven consecutive patients, 9-81 years old, with cystic mass lesions of the brain and neurologic symptoms and signs directly related to the masses. Axial contrast-enhanced T1-weighted images were obtained in six patients, surgical exploration was done in five patients, and stereotaxic biopsy was done in two. After examination of the routine spin-echo and SSFP images, the usefulness of SSFP images was determined by how well they facilitated correct preoperative diagnosis., Results: On SSFP MR images, the solid or inhomogeneous components of a cystic mass had extremely low signals in contrast to the high signal of surrounding fluid. On routine spin-echo images, however, the signals of these components were masked by the signal of the surrounding fluid. SSFP MR images helped markedly in diagnosis of hemorrhagic, epidermoid, and arachnoid cysts. In cases of enhancing brain tumors, SSFP MR images provided the same information that contrast-enhanced images did. Overall, when SSFP MR imaging was used, more information about the texture and constituents of the cystic mass was obtained, and a more useful diagnosis was made., Conclusion: Initial results show that SSFP MR imaging is a more useful technique than conventional spin-echo imaging for characterizing complex cystic masses of the brain. SSFP MR imaging (1) allows distinction of edema from tumor, (2) helps establish where biopsy has the best chance of providing tissue that will show pathologic changes, and (3) helps distinguish simple cysts from tumors, tumor-cyst, or multicompartmental cyst and may be particularly helpful in detecting the contents of hemorrhagic cysts.

This study demonstrates the use of diffusion-weighted MR imaging in improving the specificity of the diagnosis of extraaxial brain tumors. Three surgically proved lesions (one arachnoid cyst and two epidermoid tumors) and two nonsurgically proved lesions (arachnoid and ependymal cysts) were evaluated with T1- and T2-weighted spin-echo studies followed by intravoxel incoherent motion (IVIM) MR imaging. The IVIM images of the lesions were displayed as an apparent diffusion coefficient (ADC) image obtained at 0.65 G/cm (maximum gradient b value = 100 sec/mm2) and compared with external oil and water phantoms. The ADC of arachnoid cysts was similar to stationary water whereas the ADC of epidermoid tumors was similar to brain parenchyma, indicating the solid nature and the slower diffusion rate of the epidermoid tumors. Cisternal CSF demonstrated uniformly high ADC, primarily because of bulk flow, which enhanced image contrast. Improved delineation of postsurgical changes was also possible. Our preliminary results show that diffusion-weighted MR imaging can be useful in distinguishing between arachnoid cysts and epidermoid tumors.

The MR images of 112 soft-tissue masses of various causes were retrospectively reviewed. Pathologic diagnosis by biopsy was available in 96 cases. Diagnosis in the remaining 16 cases was established by characteristic radiographs, CT scans, and/or arteriograms, in conjunction with appropriate history and clinical follow-up. All masses were evaluated with both T1-weighted, 300-600/20-30 (TR/TE), and T2-weighted, 2000/80-100, images. They were reviewed to determine (1) if these images were sufficiently unique to allow a preoperative diagnosis based exclusively on the MR appearance and (2) if benignity vs malignancy could be predicted on the basis of the analysis of the MR image characteristics of the lesion. Concerning the latter, attention was directed to the margins of the lesions, to the impact of the lesion on the surrounding tissues (edema, infiltration, etc.), and to the intensity and homogeneity of the MR signal of the lesion. MR images were sufficiently characteristic to allow a specific diagnosis in 27 (24%) of the 112 cases (10 lipomas, eight hemangiomas, six pigmented villonodular synovitis, two hematomas, and one arteriovenous malformation). MR was incapable of reliably distinguishing between benign and malignant soft-tissue tumors.