Desmoplastic fibroma with perineural spread: conventional and diffusion-weighted magnetic resonance imaging findings

. In the present case, catheterization of umbili-cal vein and artery was performed with two hours of life; but thelate symptoms onset and the exploratory laparotomy demonstratedthat the catheterization was not related to the MD perforation.Hirschsprung’s disease may also predispose to MD perfora-tion due to delayed passage of meconium, determining increasedpressure upstream of the diverticulum

is the most common symptom, usually occurring as a result from inflammation or ileal volvulus (1,4) . Meckel's diverticulum rupture is rarely found in neonates, occurring in less than 10% and manifesting at radiography as pneumoperitoneum (1) . In such situations, the differential diagnosis should be made with necrotizing enterocolitis, since this disease is responsible for 41% of cases of neonatal pneumoperitoneum (4) .
In the present case, there was a clinical suspicion of necrotizing enterocolitis, but this hypothesis was ruled out as the presence of a perforated MD was intraoperatively confirmed.
The causes of MD include inflammatory reaction, mucosal ulceration and defective muscular layer of the diverticulum (1,2) . Rarely, MD perforation may occur as a result from umbilical catheterization by means of an umbilical vein connection with the MD via umbilical cord (6) . In the present case, catheterization of umbilical vein and artery was performed with two hours of life; but the late symptoms onset and the exploratory laparotomy demonstrated that the catheterization was not related to the MD perforation.
Hirschsprung's disease may also predispose to MD perforation due to delayed passage of meconium, determining increased pressure upstream of the diverticulum (5) . Such a condition occurs with typical symptoms of bowel obstruction, abdominal pain and bilious vomiting (5) . In the present case, despite the symptoms of bowel obstruction and abdominal discomfort at palpation, bilious vomiting was not observed. Furthermore, the histopathological analysis of the surgical specimen ruled out the hypothesis of Hirschsprung's disease.
Finally, MD should be included as a diagnostic hypothesis in the absence of other factors that might justify the presence of pneumoperitoneum in a neonate. Such a complication is confirmed by means of a surgical procedure.

Dear Editor,
A male, three-year-old child with morphostructural alteration developed over the last year in the region of the mandible at left, presenting with recent onset of pain, with no other associated complaints. Laboratory tests did not demonstrate any alteration and magnetic resonance imaging (MRI) ( Figure 1) showed a lesion with predominant iso/hyposignal on T1-weighted image, hypersignal on T2-weighted image with subtle low signal intensity foci, absence of signal loss on susceptibility-weighted se-quences and absence of diffusion restriction. After gadolinium injection, exuberant enhancement was observed in addition to perineural dissemination through the third division of the trigeminal nerve. Histopathological analysis revealed spindle cells without atypias and pleomorphism, besides areas with acellular fibrous connective tissue, with immunohistochemical negative for S100, and positivity for vimentin and SMA, with Ki-67 < 5%. Such findings are compatible with desmoplastic fibromas. The patient was submitted to incomplete surgical excision supplemented with radiotherapy.
Desmoplastic fibroma is an extremely rare, benign bone tumor with aggressive and usually insidious behavior, representing 0.1% of all primary bone tumors (1)(2)(3)(4)(5) . The mandible is the most affected site, particularly in its posterior portion, corresponding to 22% of cases (1,2,4) , followed by the metaphyseal region of long  bones. Desmoplastic fibromas may occur at any age range, although its higher incidence is observed at the first three decades of life (1)(2)(3)6) . Despite conflicting data, it seems there is no predilection for sex (2,6) . Local recurrence is frequently observed in cases where complete resection is not. Clinically, the patients are either asymptomatic or may present with pain, edema, joint effusion and pathological fracture (1)(2)(3)(4)(5)(6) . The differential diagnosis should consider rhabdomyosarcoma, fibrosarcoma, giant cell tumor, among others. Despite the imaging methods usefulness in the lesion delimitation, the diagnosis is histopathological. At MRI, most lesions present with iso/hyposignal on T1weighted images and low signal intensity on T2-weighted images (1,(3)(4)(5)(6) , but there are reports of lesions with hypersignal on T2weighted images (1)(2)(3)6) . The enhancement may be variable, and according to some authors, such variation may be a result of the cellular content of the lesion (3,4) . In the present case, there was homogeneous iso/hyposignal on T1-weighted images and subtle hypersignal on T2-weighted images, with foci of low signal intensity. After gadolinium injection, marked contrast enhancement, with noticeable perineural dissemination through the third division of the trigeminal nerve were observed. Such aspects on T2weighted sequences, and the presence of perineural dissemination are not commonly observed as compared with the typical imaging pattern described at MRI.
Reports on diffusion in desmoplastic fibromas were not found in the literature. In the present case, areas of diffusion restriction were not observed. Recent studies highlight the use of diffusionweighted imaging in the evaluation of head and neck lesions, showing that apparent diffusion coefficient < 1.22 × 10 -3 mm 2 /s are suggestive of malignancy (7) . In the present case, the value for apparent diffusion coefficient was 1.45 × 10 -3 mm 2 /s, corroborating the previously described findings.

Dear Editor,
A 72-year-old woman with rapidly progressive dementia, behavioral changes and apraxia of gait for seven months, extrapyramidal signs and diffuse myoclonus. Electroencephalography dem-onstrated periodic electric activity with high amplitude acute phase waves diffusely distributed over the cortex. The cerebrospinal fluid was normal. Magnetic resonance imaging (MRI) was performed ( Figure 1).
The association of clinical, radiological, electroencephalic or cerebrospinal fluid findings (presence of 14-3-3 brain protein in diseased patient for less than two years -absent in this case), Figure 1. A: Axial magnetic resonance imaging of the skull demonstrating foci of hypersignal at diffusion-weighted sequences in the heads of the caudate nuclei, putamina, thalami and medial occipitotemporal gyri. B: At the ADC mapping, the low signal intensity in the same region confirms the diffusion restriction.
A B