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A 57-year-old woman with a history of previous bilateral breast polyacrylamide hydrogel injection presented for 18F-FDG PET/CT imaging to investigate recurrent retroperitoneal liposarcoma. Incidental symmetrical FDG-positive accumulation was noted in the bilateral axillae tracking between the interpectoral planes. The finding is consistent with a chronic inflammatory process secondary to the migration of the polyacrylamide hydrogel injections.

Two patients with diffuse large B-cell lymphoma relapsing as neurolymphomatosis diagnosed on FDG PET/CT are presented. Both patients were treated initially with chemotherapy and had a complete metabolic response. Patient 1 represented with lower-limb pain. An FDG PET/CT demonstrated intense uptake throughout the sciatic nerves bilaterally extending distally with relapse confirmed on biopsy. Patient 2 represented to hospital with worsening mobility, neuropathic pain, and facial asymmetry. An FDG PET/CT demonstrated relapse within the spinal cord, left sciatic nerve, and facial nerve branches. Neurolymphomatosis is an uncommon finding on FDG PET/CT and can be the only site of relapse.

A 64-year-old woman with metastatic clear cell renal carcinoma who had been on nivolumab immunotherapy for 10 months was referred for a FDG PET scan to monitor disease progress. New bilateral mediastinal and hilar FDG-avid lymphadenopathy was noted. Pathology on subsequent mediastinal nodal biopsy showed well-formed epithelioid granulomas with no evidence of malignancy consistent with sarcoidosis. This case illustrates that pulmonary sarcoidosis can be induced by immunotherapy in the treatment of renal cell carcinoma.

Hepatic pyocyst is a rare but potentially life-threatening complication of autosomal dominant polycystic kidney disease. With extensive hepatic cystic disease, localization of a pyocyst and targeted aspiration or drainage is often a diagnostic challenge. Two patients with autosomal dominant polycystic kidney disease and recurrent gram-negative sepsis were imaged with Ga SPECT/CT for investigation of an infective source. In both patients, imaging accurately localized infected pyocysts and guided percutaneous drainage and further management.

Metastatic neureoendocrine tumor to bone is well recognized. Typically, this has an appearance of multiple focal lesions. We present an example of diffuse skeletal involvement on both F-FDG PET/CT and Ga DOTATATE PET/CT with a pattern similar to the superscan appearance described on skeletal scintigraphy.

Ga prostate-specific membrane antigen (PSMA) PET/CT is increasingly used to evaluate extent of disease in prostate carcinoma. Several other benign and malignant pathologies have also been reported to demonstrate PSMA avidity. We present a case of serous cystadenoma of the pancreas showing focal uptake on PSMA PET/CT.

The excretion of Ga-DOTA-Octreotate (DOTATATE) and related somatostatin analogues in breast milk has not been demonstrated. We report a case of a 34-year-old woman, 7 months postpartum and breastfeeding, who was referred for DOTATATE imaging after the diagnosis of appendiceal carcinoid and subsequent appendectomy. Prominent breast uptake was noted. A breast milk sample from the patient at 90 minutes postinjection was assayed in a gamma counter and shown to have a concentration of 5.6 Bq/g per MBq administered. The excretion of DOTATATE in breast milk is important to consider when providing radiation safety advice to breastfeeding patients.

Ga DOTATATE PET/CT is an imaging technique used in the diagnosis of neuroendocrine tumors. We report a case of 66-year-old woman with a history of surgically removed renal cell carcinoma who presented for a DOTATATE PET/CT scan to characterize a newly diagnosed pancreatic lesion. DOTATATE-avid lesions were identified in the thyroid gland and pancreas. Subsequent biopsy confirmed the diagnosis of metastatic renal cell carcinoma at both sites. It is important to be aware that tumors other than neuroendocrine tumors may also show uptake on DOTATATE PET/CT scan. A biopsy may be required if lesions are identified at atypical sites.

Ga prostate-specific membrane antigen (PSMA) PET/CT is a new imaging technique that is significantly more sensitive to prostate cancer lesions than other conventional imaging modalities. Various other benign and malignant neoplasms may also express PSMA and show uptake on PSMA PET/CT scan. We report a case of 66-year-old man who had a PSMA PET/CT scan for restaging of prostate carcinoma. A PSMA-avid left femoral lymph node was identified. Subsequent biopsy confirmed the diagnosis of follicular lymphoma. It is important to be aware of this possibility to avoid scan misinterpretation. Biopsy of any atypical or clinically unexpected lesions should be considered.

Ga-PSMA PET/CT is a new imaging technique that is highly sensitive to metastatic prostate cancer lesions compared with other conventional imaging modalities. We report a case of a 77-year-old man with newly diagnosed prostate carcinoma who had a PSMA PET/CT scan for staging of his disease. An intensely PSMA-avid right pelvic mass was identified abutting the cecum and terminal ileum. Surgical removal and histopathologic examination of this lesion revealed the diagnosis of a desmoid tumor. It is important to be aware that many tumors other than prostate carcinoma may also show avid uptake on PSMA PET/CT scan.

68Ga-prostate-specific membrane antigen (PSMA) PET/CT imaging is a relatively new imaging technique used to evaluate the extent of disease in prostate carcinoma. Various other neoplasms may also express PSMA and show uptake on PSMA PET/CT scan. We report a case of a 62-year-old man who had a PSMA PET/CT scan for restaging of prostate carcinoma. A PSMA-avid thyroid lesion was identified, and subsequent tissue sampling confirmed the diagnosis of follicular thyroid adenoma. It is important to be aware of this possibility to avoid scan misinterpretation. Tissue biopsy of PSMA-avid thyroid lesions should be considered to exclude a primary thyroid neoplasm.

A 50-year-old male patient with a history of medullary thyroid cancer and extensive previous investigation including FDG PET 18 months earlier presented for a Ga-dotatate scan. A single area of abnormal uptake was identified in the right ninth rib. An MRI scan and bone scan confirmed the bony metastasis; however, the MRI of the liver demonstrated multiple liver metastases not apparent on the PET study. These remained occult despite coregistration of the MRI and PET data. The occult nature of these lesions may have been due to a similar degree of uptake in the liver and metastases.

Current surgical techniques in patients with differentiated thyroid cancer can leave little or no remnant tissue. Coupled with favorable prognostic factors, this subgroup of patients might not require radioablative remnant ablation with Iodine-131 (I-131). Postoperative scanning may help to identify this subgroup, however low dose I-131 can lead to stunning and suboptimal response to ablative therapy. Iodine-123 (I-123) can be used but is expensive and supply can be limited. We investigate technetium-99m pertechnetate (pertechnetate) as a potential alternative for remnant scintigraphy post-thyroidectomy.Seventy consecutive post-total-thyroidectomy patients were evaluated retrospectively. Preablative pertechnetate scans of the thyroid bed were viewed blindly then directly compared with postablative I-131 scans.For patients with unequivocally positive pertechnetate uptake, the sensitivity was 81% (patients), 61% (sites), and the PPV was high (100% patients, 95% sites). In patients with either definite or equivocal pertechnetate uptake, the sensitivity was 90% (patients), 68% (sites), and the PPV was also high (100% patients, 81% sites).Pertechnetate had reasonable correlation with postablative I-131 scans with a moderately high sensitivity and a very high PPV. A positive pertechnetate scan is therefore sufficient to guide progression to I-131 ablation in most patients. When the scan is equivocal or negative, diagnostic imaging with radioiodine may be required. Pertechnetate scintigraphy may be of particular benefit if it is considered desirable to avoid I-131 in post-thyroidectomy remnant imaging.