Bronchoalveolar carcinoma of lung masquerading as iodine avid metastasis in a patient with minimally invasive follicular carcinoma of thyroid.

A 52-year-old man with follicular thyroid carcinoma was administered 182 mCi of radioiodine (I-131) a month after total thyroidectomy. Post-therapy scan revealed diffuse uptake of radioiodine in the apical left lung. CT-guided biopsy of this mass revealed mucinous bronchoalveolar carcinoma. Immunohistochemistry for thyroglobulin was negative. An FDG PET scan showed avid uptake in the lung mass. Surgery was ruled out, so he was given chemotherapy, without benefit. The lesion continued to show I-131 uptake even while on daily T3 substitution, suggesting that the mass was thyroid stimulating hormone-independent. Because the mass showed I-131 uptake and chemotherapy was not beneficial, it was decided to treat with I-131. He was continued on T3 substitution therapy and was given 209 mCi of I-131. Follow-up CT scan a few weeks later reported a 1-cm all round reduction of the mass. I-131 scan showed avid tracer uptake in the mass. This case suggests the possibility of this therapeutic option in nonthyroidal tumors that may concentrate radioiodine.

Early documentation of therapeutic response at 6 weeks following corticosteroid therapy in extensive sarcoidosis: promise of FDG-PET.

A 52-year-old man, who was treated with antitubercular drugs for 1 year without any benefit for an initial diagnosis of tuberculosis, and was referred for further evaluation. An FDG-PET study was performed to evaluate the whole-body disease status, which showed multiple abnormal foci in bilateral neck nodes, mediastinal, axillary, and multiple abdominal (para-aortic and inguinal) nodes, and the liver, spleen, and thyroid. A rebiopsy of the inguinal nodes for a definitive diagnosis was confirmatory of sarcoidosis. He had a history of hypothyroidism, which is a frequent accompaniment of sarcoidosis due to the association of autoimmunity in this population. He was treated with oral corticosteroids and was referred for reassessment of his disease status with FDG-PET following 6 weeks of therapy. The FDG-PET images showed remarkable improvement with near total resolution of the FDG hypermetabolism at the initially involved sites. The present case underscores the value of FDG-PET imaging in whole-body monitoring of early response to therapy in patients of sarcoidosis (particularly those with extensive disease) that can be of substantial benefit and indicates the promise of this powerful molecular imaging technique in managing this multisystem disorder.

"Meckel scan" findings in an infant with ileocolic intussusception.

A 7-month-old male infant who presented with bleeding per rectum was evaluated and diagnosed to have ileocolic intussusception on ultrasonography. Despite ultrasonography-guided saline reduction, there was persistence of bleeding per rectum. He was given blood transfusion and referred for Tc-99m pertechnetate scan to rule out ectopic gastric mucosa. The scan was done as per the standard institution protocol and the images revealed a focus of progressively increasing tracer uptake in the right lower abdominal quadrant suggesting the presence of ectopic gastric mucosa. An exploratory laparotomy revealed ileocolic intussusception secondary to Meckel diverticulum acting as a pathologic lead point (PLP). A wedge resection of the intestinal wall containing the diverticulum with suture closure was performed. The presence of Meckel diverticulum and ectopic gastric mucosa was confirmed on subsequent histopathological examination of the specimen. The patient rapidly improved postoperatively and was discharged 9 days after surgery. Bleeding per rectum can be seen in both intussusception and in Meckel diverticulum with ectopic gastric mucosa. Intussusception originating from a Meckel diverticulum as PLP remains a diagnostic challenge because of the overlapping symptoms.The Meckel scan findings, in this case, avoided the further CT scan, angiography, and endoscopy for the diagnosis of the cause of symptoms, sparing not only the time but cost of investigations and unnecessary radiation exposure to the patient.

Detection of superior sagittal sinus thrombosis on FDG PET.

A 51-year-old woman with infiltrating ductal carcinoma of left breast, who postsurgery, chemotherapy, and external radiotherapy presented with recurrence in the right chest wall a year after completion of treatment. An excision biopsy of the right chest wall nodule showed deposits of infiltrating ductal carcinoma. She also complained of excruciating headache. A FDG PET scan was done an hour after intravenous administration of 444 MBq (12 mCi) of F-18 FDG, on a dedicated PET scanner. The scan showed multiple hypermetabolic sites in the mediastinum, liver, spleen, abdomen, right scapula, and right ilium. In addition to all this, a triangular area of uptake was seen along the falx in the region of the superior sagittal sinus. A CT scan confirmed a superior sagittal sinus thrombosis. On contrast-enhanced CT scan an "empty delta sign" was observed in the superior sagittal sinus from enhancement of the dural leaves surrounding the comparatively less dense thrombosed sinus. This sign is highly diagnostic for sagittal sinus thrombosis.

Early response assessment in gastrointestinal stromal tumors with FDG PET scan 24 hours after a single dose of imatinib.

Gastrointestinal stromal tumors (GIST), rare mesenchymal tumors of the gastrointestinal tract, are gaining the interest of researchers because of the impressive metabolic response to the targeted molecular therapeutic drug imatinib mesylate. FDG PET is now routinely used to assess treatment response in cases of GIST because this has proven to give metabolic information, which demonstrates response earlier than anatomic imaging modalities. A 50-year-old man presented with abdominal pain and the CT scan showed a large lobulated heterogeneously enhancing mass in the abdomen. Fine needle aspiration cytology (FNAC) confirmed GIST with strong immunoreactivity to C-Kit protein. A baseline FDG PET done before initiation of therapy showed intense nonhomogenous FDG uptake in the mass (standard uptake value maximum, SUVmax of 13.45). A whole body FDG PET, repeated 24 hours after a single dose of imatinib mesylate 400 mg, showed a significant reduction in FDG uptake with a SUVmax of 4.26.

Unsuspected second malignancy detection by FDG PET scan.

A whole body F-18 FDG PET scan was done on a 45-year-old man with a small cell carcinoma of the left lung for a metastatic survey. Imaging showed intense uptake in the left lung (maximum standardized uptake value (SUVmax) of 8.32 corrected for body weight), at the site of the primary and in the hilar lymph nodes. Focal intense uptake was also seen in the rectum (SUVmax of 21.73 corrected for body weight). No anatomic imaging for the pelvis was done, as the patient had no bowel symptoms. Posttreatment PET scan done 9 months after the first scan showed significant reduction in the primary mass in the lung (SUVmax 4.45) but an increase in the rectal mass (SUVmax 83.22). He now complained of bleeding per rectum. Colonoscopy and CT scan of the abdomen showed a mass in the rectum, which on biopsy revealed invasive adenocarcinoma.