Cutaneous Sarcoidosis Evaluated by FDG PET

A Rare Widespread Cutaneous Langerhans Cell Histiocytosis Manifested on 18 F-FDG PET/CT

ABSTRACT

Widespread cutaneous involvement of Langerhans cell histiocytosis is rare. Here, we report the case of a patient with cutaneous Langerhans cell histiocytosis, which showed a large number of small high 18 F-FDG-avid foci all over the body skin on PET/CT, accompanied with involved lymph nodes in bilateral axillas.

Utility of PET/Computed Tomography in Infection and Inflammation Imaging

The role of nuclear medicine for noninvasive assessment of infection and inflammation is well established. The role of nuclear medicine is limited to initial diagnosis, recurrence, and response assessment of infections and inflammations such as tuberculosis, sarcoidosis, vasculitis, osteomyelitis, immunoglobulin G4-related diseases, and coronavirus disease 2019, as the specificity is affected by false positivity due to physiologic fluorodeoxyglucose uptake in specific organ and nonspecific uptake in postoperative cases. PET with fludeoxyglucose F 18/CT is a well-established modality for diagnosis of fever of unknown origin helping in optimized management of the patient.

Multiple Cutaneous Leiomyomas Showing Increased FDG Uptake

Cutaneous leiomyomas are rare, sporadic, or inherited benign tumors arising from smooth muscle cells of the skin associated with various disorders. We present a case of multiple cutaneous leiomyomas showing increased FDG uptake with SUVmax of 19.9. This case indicates cutaneous leiomyoma should be considered as a rare differential diagnosis in patients with hypermetabolic cutaneous lesions. Careful correlation with clinical history is needed to avoid misdiagnosis.

FDG-Avid Keloid on PET/CT Imaging

Keloid is a benign fibroproliferative growths resulting from an overexuberant healing response. A 51-year-old man with a 20-year history of keloid formation presented with a 1-year history of unexplained progressive weakness of both lower limbs. He was clinically suspected of having paraneoplastic neurologic syndrome. FDG PET/CT was performed to exclude underlying malignancy. FDG PET/CT revealed a giant FDG-avid keloid in the anterior chest wall without any other abnormal FDG uptake in the body. We emphasize that a benign FDG-avid keloid should be considered in the differential diagnosis of FDG-avid cutaneous lesions on PET/CT.

Blastic Plasmacytoid Dendritic Cell Neoplasm Evaluated by FDG PET/CT

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematological malignancy. A 34-year-old man with a biopsy-proven BPDCN underwent FDG PET/CT for staging. FDG PET/CT revealed multiple mild FDG-avid cutaneous lesions on the chest and back, involvement of left inguinal lymph node, and a markedly increased FDG-avid subcutaneous mass in the left lower leg.

[(18) F]-Fluorodeoxy-d-glucose uptake-positive seborrhoeic keratosis on positron emission tomography may result from high expression of glucose transporter

[(18) F]-Fluorodeoxy-d-glucose (FDG) positron emission tomography-computed tomography (PET-CT) is known to be highly accurate in differentiating benign lesions from malignant lesions. In rare cases, benign tumours, viral infections and sarcoidosis of the skin have been reported to show FDG uptake, but the mechanism remains unclear. Here we report the first documented case of seborrhoeic keratosis (SK) showing increased FDG uptake. FDG PET-CT can be used to detect enhanced glycolysis of tumour cells by measuring increased levels of glucose transporters (GLUTs) indicative of higher glucose uptake. GLUT1 and GLUT3 expression in this case was compared with that in PET-negative SK and two normal skin samples using quantitative polymerase chain reaction with paraffin-embedded tissue. The expression of GLUT1 and GLUT3 was higher in PET-positive SK than in PET-negative SK or normal skin. More specifically, the expression of GLUT3 was observed only in the PET-positive case. This study revealed that high GLUT1 and GLUT3 expression in SK might be associated with the uptake of FDG.

Flip-flop phenomenon in systemic sclerosis on fluorodeoxyglucose positron emission tomography/computed tomography

Systemic sclerosis (SSc) is a rare autoimmune disease, which may affect multiple organ systems. Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) can demonstrate the degree and anatomical extent of involvement in the entire body and coexisting malignancies in connective tissue diseases. We present a case of SSc with an increased 18F-FDG uptake in the cutaneous and subcutaneous tissues even higher than the neighboring skeletal muscles (“flip-flop phenomenon,” that is, an increased 18F-FDG uptake in the skin but a decreased 18F-FDG uptake in the skeletal muscles).

Growing applications of FDG PET-CT imaging in non-oncologic conditions

As the number of clinical applications of 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography (PET-CT) grows, familiarity with the conditions that can be diagnosed by this modality and when relevant pieces of additional information can be obtained becomes increasingly important for both requesting physicians and nuclear medicine physicians or radiologists who interpret the findings. Apart from its heavy use in clinical oncology, FDG PET-CT is widely used in a variety of non-oncologic conditions interconnecting to such disciplines as general internal medicine, infectious diseases, cardiology, neurology, surgery, traumatology, orthopedics, pediatrics, endocrinology, rheumatology, psychiatry, neuropsychology, and cognitive neuroscience. The aim of this review was to summarize the current evidence of FDG PET-CT applications in evaluating non-oncologic pathologies and the relevant information it can add to achieve a final diagnosis.

Solitary subcutaneous gouty nodule mimicking metastatic melanoma on FDG PET/CT

A 68-year-old man with a history of malignant melanoma in the right axilla underwent FDG PET/CT. The images demonstrated a focally increased activity in the subcutaneous tissue anterior to the distal left tibia, suggestive of metastasis. However, a gouty tophus was diagnosed pathologically after biopsy.

Extensive invasive extramammary Paget disease evaluated by F-18 FDG PET/CT: a case report

Extramammary Paget disease (EMPD) is a rare cutaneous, intraepithelial adenocarcinoma. Because of its rarity, little is known about the value of fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in evaluating this disease. Our case report aims to increase current knowledge of FDG PET/CT in EMPD as a noninvasive imaging tool for assessing the extension of the disease and detecting distant metastases.We reported a 64-year-old Chinese man who presented with a slowly progressive, ill-margined erythematous lesion with a crusted, eroded, and scaly surface involving multiple sites of penis, scrotum, left pelvic wall, hip, groin, and thigh for >4 years, which became extensive in the past 1 year. He was referred for an FDG PET/CT examination to further evaluate the lesions. A following skin biopsy was performed to obtain a definitive histological diagnosis.FDG PET/CT imaging revealed mild FDG uptake at the extensive cutaneous lesion with subcutaneous invasion, involvement of lymph nodes, and multiple intense FDG-avid of skeletal metastases. According to the appearance of FDG PET/CT, a provisional diagnosis of advanced cutaneous malignancy was made. Histopathology findings indicated characteristic of EMPD. The patient was treated with radiation therapy and died from complications 2 months after the last dose of radiotherapy.Our case highlighted that a whole-body FDG PET/CT should be incorporated into the diagnostic algorithm of EMPD to give a comprehensive assessment of this disease.

18F-FDG PET/CT findings in a patient with Sweet syndrome associated with myelodysplastic syndrome

A 73-year-old man was admitted to our hospital because of a 2-year history of repeated painful edematous erythemas on the skin and pancytopenia for the last 8 months. FDG PET/CT demonstrated multiple cutaneous foci with increased tracer accumulation throughout the body, multiple FDG-avid lymph nodes in the mediastinum, bilateral pulmonary hili and abdomen, and diffusively increased FDG uptake of bone marrow. A skin biopsy revealed infiltration by neutrophilic granulocytes consistent with Sweet syndrome. Myelodysplastic syndrome was established on bone marrow aspiration and biopsy.

Increased FDG uptake in scrotal steatocystoma multiplex with calcification

Steatocystoma multiplex is a rare, benign, sporadic or familial disorder. Steatocystoma multiplex with extensive calcification is extremely rare. A 57-year-old man presented fever and cough with expectoration for 3 weeks. Chest CT showed bilateral pleural effusion. FDG PET/CT showed diffuse FDG uptake of the bone marrow and multiple hypermetabolic calcified nodules in the scrotum with SUVmax of 7.6. Blood culture revealed septicemia. Skin biopsy of the scrotal nodules revealed steatocystoma multiplex with calcification. Histopathologically, there were rich multinucleated giant cells and lymphocytes in the cyst wall of the steatocystoma, which may contribute to the increased FDG uptake.

Increased FDG activity in a dermatofibroma in esophageal cancer patient

PET using the radiotracer (18)F-FDG is used for staging patients with esophageal cancer. Nonmalignant conditions, mainly inflammation and some benign tumors, however, can cloud the clinical picture by taking up FDG and producing a false-positive result. We report the case of a 46 year-old man with squamous cell carcinoma of the thoracic esophagus who underwent combined PET/CT and had false-positive uptake in a chest wall dermatofibroma. Dermatofibroma is a benign skin lesion with a characteristic large presence of fibroblasts and macrophages. Macrophage uptake of FDG is likely responsible for the false-positive result on PET/CT.

PET/CT in Patients with Sarcoidosis or IgG4 Disease

Sarcoidosis as a distinct disease entity was diagnosed more than 100 years ago. The signs and symptoms of the disease are nonspecific, posing a challenge for early and accurate diagnosis. IgG4 disease or syndrome has various clinical manifestations, such as sclerosing pancreatitis, sclerosing cholangitis, prostatitis, tubulointerstitial nephritis, interstitial pneumonia, and enlargement of salivary glands. This article discusses the role of the different diagnostic imaging modalities in sarcoidosis and IgG4 disease, including radiographs, computed tomography, magnetic resonance imaging, and conventional nuclear medicine, with a special emphasis on positron emission tomography as a superior modality for assessing these inflammatory diseases.