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Purpose: To compare diagnostic performance between computed tomography (CT) and magnetic resonance imaging (MRI) for the detection of bone infiltration from oral cancer, and to test interobserver agreement between radiologists with different expertises., Materials and Methods: Pre-surgical CT and MRI were reviewed independently by two radiologists with different expertises in head and neck oncology. A third radiologist reviewed CT and MRI simultaneously. Interobserver agreement was calculated by Cohen test. Association between radiological evidence of bone infiltration and histological reference was tested by Fisher's exact test or Chi-squared test, as appropriate. Receiving operator curve was calculated and area under the curve (AUC) was compared between CT, MRI, and both methods together., Results: Interobserver agreement was moderate: the trainee under-reported periosteal reaction on CT and inferior alveolar canal involvement on MRI. Imaging findings associated with histologic evidence of bone infiltration were: periosteal reaction and cortical erosion on CT; bone marrow involvement, contrast enhancement within bone; and inferior alveolar canal involvement on MRI. Sensitivity of MRI alone (74 %) was higher than CT (52 %). Simultaneous review of CT and MRI showed the highest specificity (91 %), with the increase of diagnostic performance in the subgroup of subjects with positive MRI (AUC = 0.689; p = 0.044)., Conclusion: Higher expertise allows pre-surgical detection of clinically relevant signs of bone infiltration sensitivity of MRI alone is higher than CT for the detection of bone infiltration from oral cancer. In MRI positive cases, diagnostic integration with combined review of CT and MRI is suggested for optimal diagnostic performance.

Introduction: The Tailgut cyst (cystic hamartoma) is an uncommon congenital disease of presacral retrorectal space and is embryologically part of some forms of enteric cysts. It is a benign malformation, although cases have been described in neoplastic degeneration., Presentation of Case: A caucasian 24 year old female presented shortly after childbirth with hypogastric abdominal discomfort associated with rectal tenderness, bleeding and moderate urinary symptoms for about three weeks. No previous similar episodes were reported. The patient was not suffering from haemorrhoids or inflammatory disease of the gastrointestinal tract. Clinical examination revealed no significant abnormalities or in the perianal area and gluteal surface. Digital rectal examination was suspicious of the presence of a presacral retrorectal mass. However, it could not exclude a trans-sphinteric perianal fistula. There was no fistulous communication with the exterior and the pain seemed to be more pronounced in the rectum. MRI, which has a diagnostic accuracy of 76-100% for the detection of any perianal fistulae, was performed and demonstrated the presence of a retrorectal cystic hamartoma (Tailgut cyst)., Discussion: The most common retrorectal space cystic lesions includes epidermoid cysts, dermoid cysts and enteric cysts. It presents with pelvic pain, and sometimes with local abscess, secondary to a sinus cyst. There can also be a communication between Tailgut cyst and fistula; in the absence of primary infection may develop postinflammatory fibrosis. Radiological investigation is carried out by TRUS, CT and MRI. During MRI, on T1-weighted images, the signal intensity may change from hypointense to hyperintense as protein concentration increases, as well as in the case of bleeding. On T2-weighted images, signal intensity of mucinous fluids can decrease from highly hyperintense to hypointense with increasing protein concentration and viscosity., Conclusion: MRI is a non-invasive useful imaging investigation with high diagnostic accuracy when a retrorectal cyst is suspected. Despite its rarity, Tailgut cyst should be considered, both for acute complications, like infection or bleeding, and for the risk, however infrequent, of neoplastic degeneration., (Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.)