Benign breast lesions detected by positron emission tomography-computed tomography

Unexpected focal fluorodeoxyglucose uptake in main organs; pass through or pass by?

Since the inception of fluorine-18 fluorodeoxyglucose (F-18 FDG), positron emission tomography/computed tomography (PET/CT) utilizing F-18 FDG has become widely accepted as a valuable imaging modality in the field of oncology, with global prevalence in clinical practice. Given that a single Torso PET/CT scan encompasses the anatomical region from the skull base to the upper thigh, the detection of incidental abnormal focal hypermetabolism in areas of limited clinical interest is both feasible and not uncommon. Numerous investigations have been undertaken to delineate the distinctive features of these findings, yet the outcomes have proven inconclusive. The incongruent results of these studies present a challenge for physicians, leaving them uncertain about the appropriate course of action. This article provides a succinct overview of the characteristics of fluorodeoxyglucose, followed by a comprehensive discussion of the imaging findings and clinical significance associated with incidental focal abnormal F-18 FDG activity in several representative organs. In conclusion, while the prevalence of unrecognized malignancy varies across organs, malignancies account for a substantial proportion, ranging from approximately one-third to over half, of incidental focal uptake. In light of these rates, physicians are urged to exercise vigilance in not disregarding unexpected uptake, facilitating more assured clinical decisions, and advocating for further active evaluation.

Breast Cancer and Physiologic Avidity From Breast Feeding on FDG PET/CT

ABSTRACT

A 35-year-old woman presented with breast cancer diagnosed during pregnancy. Eleven days after delivery, the patient underwent FDG PET/CT for systemic staging. Avidity was seen diffusely in both breasts, with a more avid focus at the site of a biopsy clip in the right breast. There were no lymph nodes or distant metastases. The patient was actively breast feeding, explaining the diffuse breast avidity. This case demonstrates both malignant and benign FDG avidity in the breasts at the same time, with a focal FDG-avid right breast malignancy identified among bilateral breast parenchyma with elevated physiologic FDG-avid secondary to breast feeding.

Clinical-Diagnostic Relevance of Breast "Incidentaloma" Detected During 18F-Fluoro-2-Deoxy-D-Glucose Positron Emission Tomography/Computed Tomography: Correlation with Radiological Imaging and Histopathology

Aim:

This study aims to study the clinical-diagnostic relevance of incidental breast uptake (“incidentaloma”) on 18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan performed for other indications and to correlate it with radiological imaging and histopathology.

Materials and Methods:

We retrospectively evaluated 3675 FDG-PET scans, identifying 43 patients with breast “incidentaloma.” Thirty of these findings were further investigated with clinical examination, mammography (MMX), UltraSound (US) and/or magnetic resonance (MR). Cases suspected for malignancy underwent US-guided macro-biopsy (USMB) or MR-guided biopsy. Correlations between FDG-PET, radiology findings, age, and histopathology were evaluated.

Results:

patients who performed both US and MMX were 19. Ten consequently underwent USMB, one MR-guided biopsy, the remaining 8 were not further investigated. Nine patients had a diagnosis of malignancy. Among 11 patients who performed only US and consequently, USMB 6 had a diagnosis of malignancy. Histopathology of the 22 patients with both morphological and glucometabolic alterations showed different types of benign or malignant neoplasia, with a cumulative 68.2% incidence of malignancy. Seven lesions showed a SUV_max >2.5, while the remaining 15 a SUV_max <2.5. There was no statistically significant correlation between SUV_max and histology, therefore SUV_max parameter should not be used to discriminate between benign and malignant findings. No significant correlation between patient age and tumor characterization was found.

Conclusions:

incidental mammary uptake during an FDG-PET scan may represent a clue suggesting to investigate PET findings. In this subset of patients, early diagnosis may lead to a change in clinical management with a favorable impact on prognosis and a significant reduction in healthcare costs.

PET/CT Variants and Pitfalls in Breast Cancers

There are a number of normal variants and pitfalls which are important to consider when evaluating F-18 Fluorodeoxyglucose (FDG) with Positron Emission Tomography (PET) in breast cancer patients. Although FDG-PET is not indicated for the initial diagnosis of breast cancer, focally increased glucose metabolism within breast tissue represents a high likelihood for a neoplastic process and requires further evaluation. Focally increased glucose metabolism is not unique to breast cancer. Other malignancies such as lymphoma, metastases from solid tumors as well as inflammatory changes also may demonstrate increased glucose metabolism either within the breast or at other sites throughout the body. Importantly, benign breast disease may also exhibit increased glucose metabolism, limiting the specificity of FDG-PET. Breast cancer has a wide range of metabolic activity attributed to tumor heterogeneity and breast cancer subtype. Intracellular signaling pathways regulating tumor glucose utilization contribute to these pitfalls of PET/CT in breast cancer. The evaluation of axillary lymph nodes by FDG-PET is less accurate than sentinel lymph node procedure, however is very accurate in identifying level II and III axillary lymph node metastases or retropectoral metastases. It is important to note that non-malignant inflammation in lymph nodes are often detected by modern PET/CT technology. Therefore, particular consideration should be given to recent vaccinations, particularly to COVID-19, which can commonly result in increased metabolic activity of axillary nodes. Whole body FDG-PET for staging of breast cancer requires specific attention to physiologic variants of FDG distribution and a careful comparison with co-registered anatomical imaging. The most important pitfalls are related to inflammatory changes including sarcoidosis, sarcoid like reactions, and other granulomatous diseases as well as secondary neoplastic processes.

New advance in breast cancer pathology and imaging

The improvement of knowledge concerning the pathology of breast cancer could provide the rationale for the development of new imaging diagnostic protocols. Indeed, as for the microcalcifications, new histopathological markers can be used as target for in vivo early detection of breast cancer lesions by using molecular imaging techniques such as positron emission tomography. Specifically, the mutual contribution of these medical specialties can ‘nourish’ the dream of a personalized medicine that takes into account the intrinsic variability of breast cancer. In this review, we report the main discoveries concerning breast cancer pathology highlighting the possible cooperation between the departments of anatomic pathology and imaging diagnostics.

A preliminary study to propose a diagnostic algorithm for PET/CT-detected incidental breast lesions: application of BI-RADS lexicon for US in combination with SUVmax

OBJECTIVES

To develop a diagnostic algorithm for positron emission tomography (PET)-detected incidental breast lesions using both breast imaging reporting and data system (BI-RADS) and maximum standardized uptake value (SUVmax) criteria.

METHODS

Fifty-six PET-detected incidental breast lesions from 51 patients, which were subsequently investigated by breast ultrasound within 1 month of the PET study, constituted the study cohort and they were finally verified by tissue diagnosis or a 2-year follow-up. Based on the maximum specificity with sensitivity > 60.0% and maximum sensitivity with specificity > 60.0%, two SUVmax cutoff values were calculated at 2 and 3.7. BI-RADS ≥ 4 was considered as highly suspicious for malignancy. The diagnostic accuracies were estimated for SUVmax levels above or below the cutoff points combined with the BI-RADS suspicion level.

RESULTS

Overall, 46 benign and 10 malignant lesions were studied. The diagnostic characteristics of SUVmax ≥ 2, SUVmax ≥ 3.7, and BI-RADS ≥ 4 were 80.0%, 60.0%, and 80.0% for sensitivity, 73.9%, 95.7%, and 92.7% for specificity, and 75.0%, 89.3%, and 90.2% for accuracy, respectively. When the SUVmax threshold was set at 2, combined with BI-RADS suspicion level, the sensitivity, specificity, and accuracy were 100.0%, 69.6%, and 75.0%, respectively. The results for SUVmax threshold set at 3.7 combined with BI-RADS were 90.0%, 91.3%, and 91.1% for the sensitivity, specificity, and accuracy, respectively. A diagnostic algorithm was accordingly generated.

CONCLUSION

The need for biopsy should be justified in low BI-RADS lesions presenting with high SUVmax at 3.7 or higher. The biopsy of patients with high B-IRADS and low SUVmax could be preserved.

KEY POINTS

• A diagnostic algorithm was developed for PET-detected incidental breast lesions using both BI-RADS and SUVmax criteria. • Diagnostic performance was calculated separately and conjunctively for SUVmax ≥ 2, SUVmax ≥ 3.7, and BI-RADS ≥ 4. • The need for biopsy can be justified in BI-RADS < 4 lesions with SUVmax ≥ 3.7. Lesions with BI-RADS < 4 and indeterminate SUVmax (2 < SUVmax < 3.7) benefit from a short-interval follow-up. BI-RADS < 4 lesions with SUVmax < 2 may confidently be scheduled for routine screening.

Spectrum of the Breast Lesions With Increased 18F-FDG Uptake on PET/CT

Interpretation of ¹⁸F-FDG PET/CT studies in breast is challenging owing to nonspecific FDG uptake in various benign and malignant conditions. Benign conditions include breast changes in pregnancy and lactation, gynecomastia, mastitis, fat necrosis, fibroadenoma, intraductal papilloma, and atypical ductal hyperplasia. Among malignancies, invasive ductal carcinoma and invasive lobular carcinoma are common histological types of breast carcinoma. Rarely, other unusual histological types of breast carcinomas (eg, intraductal papillary carcinoma, invasive micropapillary carcinoma, medullary carcinoma, mucinous carcinoma, and metaplastic carcinoma), lymphoma, and metastasis can be the causes. Knowledge of a wide spectrum of hypermetabolic breast lesions on FDG PET/CT is essential in accurate reading of FDG PET/CT. The purpose of this atlas article is to demonstrate features of various breast lesions encountered at our institution, both benign and malignant, which can result in hypermetabolism on FDG PET/CT imaging.

Can positron emission mammography help to identify clinically significant breast cancer in women with suspicious calcifications on mammography?

OBJECTIVE

To evaluate the diagnostic accuracy of positron emission mammography (PEM) for identifying malignant lesions in patients with suspicious microcalcifications detected on mammography.

METHODS

A prospective, single-centre study that evaluated 40 patients with suspicious calcifications at mammography and indication for percutaneous or surgical biopsy, with mean age of 56.4 years (range: 28-81 years). Patients who agreed to participate in the study underwent PEM with 18F-fluorodeoxyglucose before the final histological evaluation. PEM findings were compared with mammography and histological findings.

RESULTS

Most calcifications (n = 34; 85.0 %) were classified as BIRADS 4. On histology, there were 25 (62.5 %) benign and 15 (37.5 %) malignant lesions, including 11 (27.5 %) ductal carcinoma in situ (DCIS) and 4 (10 %) invasive carcinomas. On subjective analysis, PEM was positive in 15 cases (37.5 %) and most of these cases (n = 14; 93.3 %) were confirmed as malignant on histology. There was one false-positive result, which corresponded to a fibroadenoma, and one false negative, which corresponded to an intermediate-grade DCIS. PEM had a sensitivity of 93.3 %, specificity of 96.0 % and accuracy of 95 %.

CONCLUSION

PEM was able to identify all invasive carcinomas and high-grade DCIS (nuclear grade 3) in the presented sample, suggesting that this method may be useful for further evaluation of patients with suspected microcalcifications.

KEY POINTS

• Many patients with suspicious microcalcifications at mammography have benign results at biopsy. • PEM may help to identify invasive carcinomas and high-grade DCIS. • Management of patients with suspicious calcifications can be improved.