Abstract
Background/Aim: [18F]2-Fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) is widely used for staging endometrial carcinoma, but false-positive findings may occur due to benign conditions. Supraclavicular nodal anthracosis is rare and can mimic distant metastasis. We report a rare case of right supraclavicular nodal anthracosis in endometrial carcinosarcoma.
Case Report: An 80-year-old woman with suspected endometrial malignancy underwent FDG-PET/CT, which demonstrated FDG uptake in the uterus and right supraclavicular, mediastinal, and hilar lymph nodes. Ultrasound-guided core needle biopsy of the right supraclavicular lymph node revealed extensive anthracotic pigment deposition without evidence of malignancy. The final diagnosis after surgery was endometrial carcinosarcoma, FIGO stage IIC.
Conclusion: Right supraclavicular nodal anthracosis may cause false-positive FDG-PET/CT findings, potentially related to lymphatic migration of carbon-laden macrophages via rare variant thoracic duct anatomy. Histologic confirmation is essential to avoid misdiagnosis and inappropriate disease upstaging.
- PET-avid anthracosis
- nodal anthracosis
- anthracosis in supraclavicular lymph node
- endometrial carcinosarcoma
Introduction
Recent large-scale epidemiologic analyses indicate that both the incidence and population burden of endometrial carcinoma (EC) have increased over recent decades, especially in the United States, with emerging shifts toward younger age groups (1, 2). The mortality rate has been rising at an average annual rate of 1.9%, largely driven by the increasing prevalence of obesity, a well-established risk factor for the most common histologic subtype of EC (3, 4). Contemporary clinical guidelines from both the United States and Europe recommend pelvic magnetic resonance imaging, abdominal and thoracic computed tomography (CT), and [18F]2-Fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET/CT) as components of the preoperative evaluation (5, 6). FDG-PET/CT has been shown to provide high specificity and positive predictive value in the detection of distant metastatic disease (7). Moreover, FDG-PET/CT demonstrates excellent diagnostic accuracy for identifying lymph node metastases in the preoperative setting in patients with EC (8).
Anthracosis is characterized by the deposition of carbon-derived pigment, typically without eliciting a significant tissue reaction. Nodal anthracosis presenting as FDG-avid mediastinal or hilar lymph nodes can occasionally be observed and may resemble infectious, granulomatous, or malignant conditions (9, 10). However, involvement of the supraclavicular lymph node is rare (11). Importantly, nodal anthracosis may appear as a false-positive finding on FDG-PET/CT during oncologic work-up, posing diagnostic challenges in distinguishing it from distant metastasis. Such misinterpretation may result in inappropriate disease upstaging and the implementation of treatment strategies that exceed the patient’s actual therapeutic requirements.
Herein, we describe a patient with anthracotic involvement of the right supraclavicular lymph node that mimicked metastatic disease from endometrial carcinoma.
Case Report
An 80-year-old woman was referred to our institution with lower abdominal discomfort. She was a nonsmoker and had lived in an urban environment. She had never been employed and had been housewife throughout her life. Her medical history was notable for pulmonary tuberculosis in her 20s and total thyroidectomy for thyroid carcinoma in 2015.
At an outpatient visit on October 30th, 2025, transvaginal ultrasonography (US) revealed marked fluid accumulation within the uterine cavity, suspicious for hematometra. In addition, heterogeneous echogenic components were observed. An attempt was made to drain the intrauterine fluid via a transvaginal approach for pathologic evaluation; however, the uterine cervix could not be identified due to severe deviation caused by marked enlargement of the uterine corpus.
Pelvic magnetic resonance imaging (MRI) demonstrated multiple enhancing lesions involving the endometrial cavity and cervical canal, with the largest lesion measuring up to 45 mm in diameter. The endometrial cavity and cervical canal were distended and filled with blood products. Based on these findings, malignant lesions involving the endometrium and cervical canal were suspected, without radiologic evidence of metastatic lymphadenopathy.
During the preoperative work-up, abdominal and chest CT revealed no remarkable findings except for a hepatic cyst and post-inflammatory fibrotic changes in left upper lobe and the superior segment of left lower lobe. The FDG-PET/CT demonstrated intense FDG uptake in uterus, with a maximum standardized uptake value (SUVmax) of 19.6. Additional FDG-avid lesions were identified in the right supraclavicular region (SUVmax 5.46) (Figure 1A), mediastinal and bilateral hilar lymph nodes (SUVmax 13.61) (Figure 1B and C), and a fibrotic lesion in the lower lobe (SUVmax 1.99) (Figure 1D). Based on the uptake pattern and imaging characteristics, the pulmonary and mediastinal findings were not considered suggestive of distant metastatic disease; however, histopathologic confirmation was recommended for the right supraclavicular lymph node.
[18F]2-Fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography demonstrating FDG-avid lymph nodes and pulmonary lesion except primary malignant lesion in uterus. (A) Right supraclavicular lymph node with increased FDG uptake, later confirmed as nodal anthracosis, (B) FDG-avid mediastinal lymph node, (C) FDG-avid bilateral hilar lymph nodes, (D) FDG uptake in a fibrotic lesion of the left lower lobe.
To further evaluate the FDG-avid right supraclavicular lymph node, US-guided core needle biopsy (CNB) was performed in an outpatient setting as a less invasive alternative to surgical excisional biopsy. On US, a 1.4 × 0.7 cm lymph node was identified in the right level IV (supraclavicular area). The node exhibited a rounded morphology rather than the typical oval shape. The internal echotexture was predominantly hypoechoic and heterogeneous, with scattered fine hyperechoic foci, and the normal echogenic fatty hilum was absent. Color Doppler imaging demonstrated no significant increase in internal vascularity. These sonographic features were indeterminate, making it difficult to distinguish the lesion from metastatic malignancy.
For the US-guided CNB, the patient was placed in the supine position with a shoulder bolster to achieve neck extension, and the head was rotated to the left to optimize exposure of the target area. Local anesthesia was administered to the skin and perinodal soft tissues using 1% lidocaine. The biopsy was performed using an 18-gauge automatic core biopsy gun with an in-plane technique to ensure continuous real-time monitoring of the needle tip. The needle trajectory was carefully oriented to avoid adjacent vital neurovascular structures. A total of five tissue cores were obtained. Post-biopsy US was immediately performed to exclude acute complications, such as pneumothorax or hematoma, and the procedure was completed without any adverse events. Histopathologic examination of the right supraclavicular lymph node demonstrated extensive anthracotic pigment deposition with dense fibrosis, without evidence of malignant tumor cells (Figure 2).
Histologic examination of the right supraclavicular lymph node. No malignant tumor cells are observed. (A) Hematoxylin and eosin staining demonstrated extensive deposition of anthracotic pigment with associated dense fibrosis. (B) Immunohistochemistry for cytokeratin showed no immunoreactivity. Scale bars: 0.1 mm.
The patient subsequently underwent exploratory laparotomy with total hysterectomy and bilateral salpingo-oophorectomy on December 19th, 2025. Frozen section analysis of the uterus, which was marked distended by hematometra, confirmed the presence of carcinoma, although the exact histologic subtype could not be determined intraoperatively. No macroscopically enlarged or palpable lymph nodes were identified in the bilateral pelvic or para-aortic regions. Pelvic and para-aortic lymphadenectomy was omitted due to concerns regarding hemodynamic instability and potential surgical morbidity. Final postoperative pathologic examination, including immunohistochemical analysis, established the diagnosis of endometrial carcinosarcoma. The depth of myometrial invasion was 3 mm out of a total myometrial thickness of 10 mm, with no endocervical stromal or lymphovascular space involvement. According to the 2023 FIGO staging system (12), the disease was classified as stage IIC. The institutional review board of Kyungpook National University Hospital approved this study (KNUH 2025-12-032).
Discussion
In this case, an 80-year-old woman with endometrial carcinosarcoma demonstrated increased FDG uptake in the right supraclavicular lymph node on FDG-PET/CT, which was subsequently confirmed as nodal anthracosis on histopathologic examination. Additional FDG-avid hilar and mediastinal lymph nodes were also observed and were considered more likely to represent anthracosis or sequalae of prior inflammatory conditions, such as tuberculosis. Because this entity can mimic distant metastatic disease on PET imaging, gynecologic oncologists may overestimate disease stage in the absence of histologic confirmation. Such misinterpretation may result in unnecessary intensification of treatment, including systemic chemotherapy or radiotherapy, thereby increasing treatment-related morbidity.
Two major questions arise from this case. The first concerns why nodal anthracosis may demonstrate increased FDG uptake on PET/CT, and the second addresses why anthracosis is identified in supraclavicular lymph nodes. First, the precise mechanism underlying FDG avidity in anthracotic lymph nodes has not yet been fully elucidated. Proposed explanations are largely indirect and include the presence of metabolically active macrophages and chronic inflammatory responses induced by carbon particles. Hewitt and colleagues demonstrated macrophage aggregation around carbon deposits on pathologic examination, which was associated with PET-avid lymph nodes in the lung, supporting the hypothesis that inflammatory cellular activity rather than carbon deposition itself accounts for FDG uptake (13).
Second, although nodal anthracosis is relatively common in hilar and mediastinal lymph nodes, involvement of supraclavicular lymph nodes has rarely been reported. Two plausible mechanisms may explain this finding: immune cell migration through pulmonary lymphatic drainage pathways (14) and anatomic variations of the thoracic duct (15). Trivedi and colleagues described immune cell trafficking through pulmonary lymphatic pathways to regional lymph nodes (14). In the lung, initial lymphatic capillaries within the parenchyma drain into collecting lymphatic vessels located along the bronchovascular bundles and interlobular septa, which subsequently convey lymph to thoracic lymph nodes and ultimately to the thoracic duct, where lymph is returned to the systemic circulation. Pulmonary lymphatics play a central role in adaptive immunity by facilitating the migration of immune cells from the lung to draining lymph nodes, where immune responses to inhaled antigens are coordinated. Dendritic cells residing in the peripheral lung continuously sample airway antigens and migrate sequentially to bronchopulmonary and mediastinal lymph nodes. Molecular tracing studies have demonstrated that, under steady-state conditions, a small population of dendritic cells migrates from the lung to mediastinal lymph nodes via lymphatic channels at regular interval (14). Lee and colleagues further demonstrated that lymphatic drainage from the lung to supraclavicular lymph nodes may occur through rare anatomic variations of the thoracic duct (15). The thoracic duct, the largest lymphatic vessel in the body, typically ascends within the mediastinum, crosses the midline at the mid-thoracic level, and terminates at the left venous angle. However, multiple anatomic variants have been described. In fewer than 6% of individuals, the thoracic duct does not cross the midline and instead terminates on the right, creating a potential lymphatic pathway to the right supraclavicular lymph node. In addition, duplication of the thoracic duct, reported in approximately 1-1.5% of cases, may permit lymphatic drainage to bilateral supraclavicular lymph nodes (15).
Based on these observations, we postulate that inhaled carbon particles were initially phagocytosed by immune cells, such as macrophages, within the hilar lymph nodes, and that these carbon-laden macrophages subsequently migrated from the hilar to the right supraclavicular lymph node via mediastinal lymph node through variant lymphatic drainage of the thoracic duct. This postulation may also provide a plausible explanation for the rarity of anthracotic involvement of supraclavicular lymph nodes.
In conclusion, we report the first case of endometrial carcinosarcoma accompanied by anthracotic involvement of the right supraclavicular lymph node, resulting in a false-positive finding on FDG-PET/CT. This finding may be explained by lymphatic migration of carbon-laden macrophages from the lung through mediastinal lymphatic pathways, potentially facilitated by rare anatomic variations of the thoracic duct. Awareness of this potential pitfall is essential for gynecologic oncologists to prevent misdiagnosis, inappropriate disease upstaging, and unnecessary intensification of treatment that may increase morbidity in patients with endometrial carcinoma.
Footnotes
Authors’ Contributions
J Lee conceived the study. CY Kim, DJ Kim, SY Park designed the figures. J Lee and SY Park drafted the manuscript. All Authors discussed the results and contributed to the final manuscript.
Conflicts of Interest
The Authors have no conflicts of interest to declare in relation to this study.
Artificial Intelligence (AI) Disclosure
During the preparation of this manuscript, a large language model (ChatGPT, Open AI) was used solely for language editing and stylistic improvements in select paragraphs. No sections involving the generation, analysis, or interpretation of research data were produced by generative AI. All scientific content was created and verified by the authors. Furthermore, no figures or visual data were generated or modified using generative AI or machine learning–based image enhancement tools.
- Received January 10, 2026.
- Revision received February 9, 2026.
- Accepted February 11, 2026.
- Copyright © 2026 The Author(s). Published by the International Institute of Anticancer Research.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
References
Jump to section
Related Articles
Cited By...
- No citing articles found.