I-131 accumulation in a benign cystic mesothelioma in a patient with follicular thyroid cancer

Radioiodine whole body scan pitfalls in differentiated thyroid cancer

PURPOSE

whole body scan (WBS) performed following diagnostic or therapeutic administration of I-131 is useful in patients with differentiated thyroid carcinoma. However, it can be falsely positive in various circumstances. We aimed to report a series of pitfalls in a clinical perspective.

METHODS

A search in the database PubMed utilizing the following terms: "false radioiodine uptake" and "false positive iodine 131 scan" has been made in January 2023. Among the 346 studies screened, 230 were included in this review, with a total of 370 cases collected. Physiological uptakes were excluded. For each patient, sex, age, dose of I-131 administered, region and specific organ of uptake and cause of false uptake were evaluated.

RESULTS

370 cases of false radioiodine uptake were reported, 19.1% in the head-neck region, 34.2% in the chest, 14.8% in the abdomen, 20.8% in the pelvis, and 11.1% in the soft tissues and skeletal system. The origin of false radioiodine uptake was referred to non-tumoral diseases in 205/370 cases (55.1%), benign tumors in 108/370 cases (29.5%), malignant tumors in 25/370 cases (6.7%), and other causes in 32/370 cases (8.7%).

CONCLUSIONS

WBS is useful in the follow-up of patients with differentiated thyroid carcinoma, however it can be falsely positive in various circumstances. For this reason, it is critically important to correlate the scintigraphic result with patient's medical history, serum thyroglobulin levels, additional imaging studies and cytologic and/or histologic result.

Benign multicystic mesothelioma and peritoneal inclusion cysts: are they the same clinical and histopathological entities? A systematic review to find an evidence-based management

PURPOSE

Peritoneal mesothelial cysts (PMC) are a clinical dilemma because of their true pathogenic nature. Many definitions have been associated with PMC, including "benign multicystic mesothelioma", "cystic mesothelioma", "multilocular peritoneal inclusion cysts", ''inflammatory cysts of the peritoneum" or "postoperative peritoneal cyst".

METHODS

We herein performed a systematic review of the literature focusing on clinical and histopathological aspects of PMC, diagnosis, and therapies. Moreover, we described our experience with a case of PMC in a young female.

RESULTS

Since there is often a history of prior surgery or inflammatory disease, most authors consider PMC of reactive origin. However, in some cases they occur without any documentable signs of disease or injury. A variety of clinical findings can complicate the preoperative assessment and a multitude of histological pictures may potentially lead to a misdiagnosis. The absence of a uniform treatment strategy and lack of long-term follow-up often hinder the accurate definition leading to unnecessary or unnecessarily aggressive therapy.

CONCLUSIONS

PMC are more common than had previously been thought. Most authors consider them non-neoplastic; thus the designation of "peritoneal inclusion cyst" is preferable. The term "mesothelioma" should be used only in cases of histological evidences of atypia. The high rates of recurrence suggest that the goal of treatment should not be necessarily complete eradication, but symptomatic relief through individualized treatment. This is a topic of particular importance, especially in young female where recurrence rates could be lower than those reported in adults and where an improperly aggressive treatment could have repercussions on fertility.

Increased 131I accumulation in the polyacrylamide hydrophilic gel used for breast augmentation

A 37-year-old woman with papillary thyroid cancer received repeat 131I therapy. The first posttherapy scan revealed only activity in the neck. However, both the second and third posttherapy scans showed intense activity in the anterior lower chest bilaterally, suggestive of breast uptake. However, the SPECT/CT images demonstrated that the iodine activity was not located in the breast tissue. Instead, the activity was inside the polyacrylamide hydrophilic gels she received 10 years ago for breast augmentation.

Oncocytoma of the parotid gland causing false-positive result on I-131 whole-body scintigraphy

A 50-year-old patient underwent near-total thyroidectomy in 1997 because of a T₁N₀M₀ follicular carcinoma in the right lobe of the thyroid gland, followed by I-131 ablation (3700 MBq). Follow-up of I-131 whole-body scintigraphy after 9 years showed pathologic uptake at the left side of the neck. Histopathologic analyses of the resected specimen suggested a cystic metastasis within the parotid gland, probably originating from thyroid carcinoma. However, the patient had been disease-free for over 9 years and thyroglobulin was undetectable in plasma. Revision of the specimen with complementary immunohistochemical staining revealed histopathologic aspects more typical of oncocytoma.