Nuclide Notes

☢️ Langerhan’s cell histocytosis ☢️ FDG PET/CT shows left mandible ramus/body expansive destructive osteolytic lesion of intense FDG uptake with soft tissue component protruding beyond the osseous margins. Additional lytic lesions of intense FDG uptake in the left parietal bone and right ilium. Biopsy revealed LCH
🗓 LCH is a tumor like disease where these cells proliferate in an uncontrollable fashion. This proliferation is accompanied by lesions or mass formation. The skeleton is the most involved organ in LCH, the cells produce prostaglandins which causes medullary bone resorption. Solitary lesions (~70%) are more common than multifocal (~17%), and the most common locations are the skull (50%), ribs/spine/pelvis/femurs (15%), humerus (7%), mandible (7%). Radiologically they have variable appearance depending on location, most commonly as lytic lesions with well defined margins and no sclerotic rims.

🖼️ Osteoid osteoma of the cervical spine — reimagined in color, tension, and anatomy.

☢️ Tibial component loosening ☢️ SPECT/CT images show abnormal alignment of the femorotibial axis, with anterior translation of the tibia relative to the distal femur. The tibial component shows excessive posterior sloping with angulation of the tibial stem penetrating through the anterior tibial cortex. There is extensive multicompartmental osteolysis at the bone-prosthesis interface of the tibial plateau and extending along the stem, corresponding to intense delayed tracer uptake. The left patella appears normal in position with diffuse intense perfusion and delayed tracer uptake marked at the superolateral facet, corresponding to subchondral cystic degeneration. There is significant suprapatellar septated synovial fluid collection with increased perfusion extending to the infrapatellar recess. Findings are consistent with tibial component loosening.
BoneScan

☢️ BIA-ALCL ☢️ Breast implant associated anapestic large cell lymphoma. FDG PET/CT scan shows minimal FDG uptake within large effusion surrounding the right breast implant. FNA demonstrated BIA-ALCL.
🗓 BIA-ALCL is a rare type of NHL that has been associated with breast implants, particularly textured implants. It is not a breast cancer but rather a cancer of the immune system that can develop in the scar tissue and fluid surrounding the implant. Can be mass forming after a median of 10 years which is less common with poorer prognosis, or surrounding effusion usually after 1 years of implantation. The incidences of lymphadenopathy is 2-12%, distant metastases is rare. FDG PET cannot differentiate between benign inflammatory or malignant effusion as mild uptake can be seen around the implant owing to benign inflammatory activity around the implant capsule.

☢️ Disseminated TB ☢️ Masquerading as metastatic disease. FDG PET/CT shows hypermetabolic elongated polypoidal upper abdominal hypodense mass (biopsy proved of pancreatic origin) with regional and abdominal lymphadenopathy, disseminated multifocal osteolytic lesions involving the axial and appendicular skeleton, several showing cortical destruction and associated soft tissue components. The lumbar spine lesions are more aggressive, with paravertebral/extraosseous soft tissue extension extending through the ipsilateral neural foramina with linear soft tissue tracking along the course of the lumbar nerve root, in keeping with perineural spread.
🗓 Disseminated tuberculosis may rarely involve the pancreas and may present as a mass forming lesion, a focal hypodense pancreatic mass, or inflammatory soft tissue fullness around the pancreatic head/body. Involvement usually occurs as part of disseminated or miliary disease rather than isolated infection, and it represents only a small fraction cases, reported around 0.2–2% in recent reviews. Pancreatic head is most commonly involved, followed by the body abdominal tail.

☢️ Solid pseudopapillary epithelial neoplasm ☢️ FDG PET/CT shows a well-defined, encapsulated pancreatic tail solid mass measuring approximately 5.9X4.3 cm. The mass exhibits peripheral and internal macrocalcifications with regions of cystic component. Appearance is in favor of SPEN of pancreas, confirmed with biopsy.
🗓 Solid pseudopapillary neoplasm (SPN) of the pancreas is a rare, benign tumor (15% malignant) that predominantly affects young women, typically in their second to fourth decades of life. Characterized by a mix of solid and cystic components, SPNs are often encapsulated and can vary significantly in size. Clinically, patients may present with nonspecific abdominal pain, a palpable mass, or be asymptomatic, with the neoplasm discovered incidentally during imaging for unrelated issues. Diagnostic imaging modalities such as CT scans and MRI can reveal the characteristic features of SPN, including a well-defined mass with solid and cystic areas, hemorrhage, and calcifications. Surgical resection is the treatment of choice and is typically curative.

☢️ Situs inversus totalis ☢️ Total transposition of the thoracic and abdominal viscera. Situs inversus is a term used to describe the abnormal anatomical positioning of the abdominal and thoracic viscera. Situs solitus is normal positioning of organs. situs inversus is usually associated with dextrocardia. Situs inversus totalis is complete transposition of abdominal and chest organs.

🧬 READ WITH ME | FDG PET/CT scan

🗓 55-year-old female with history of ovarian serous cystadenocarcinoma, referred for staging.

☢️ Findings: there is a hypermetabolic complex bilateral adnexal soft tissue mass of intense FDG uptake [SUVmax= 17.2] collectively measuring 11X9.2 cm. There are multiloculated cystic component with variable internal septation and subtle calcifications, and irregular solid mural soft tissue component. The mass is invading the right mesorectal fascia and mesore**um with fat infiltration, with no clear intervening plane with the re**um.

Enlarged retroperitoneal lymph nodes of intense FDG uptake [SUVmax= 10.5] in the aortocaval and lateral para-aortic compartments.

There is a large right mesenteric lobular soft tissue mass of intense FDG uptake [SUVmax= 11.6] with regions of cystic degeneration measuring 7.1X6.3 cm. The mass is approaching the transverse colon with no clear intervening plane. Adjacent enlarged mesenteric lymph node of intense FDG uptake [SUVmax= 8.5].

☢️ Vertebral hemangioma ☢️ Early phase SPECT/CT shows intense perfusion to L3 vertebral body low density lesion. The delayed phase shows mild tracer uptake in L3 vertebral body lesion in the right middle column with coarse vertically oriented trabeculations, extending posteriorly to the left pedicle. The cortex is grossly intact without periosteal reaction or associated soft tissue component.
🗓 Vertebral hemangiomas are the most prevalent noncancerous lesions affecting the spine. The formation of new blood vessels within the hemangioma triggers osteoclastic activity which results in the degradation of cancellous bone, leading to the formation of areas of lucencies and thickened trabeculae. In atypical hemangiomas, they manifest as expansive lucent masses within the vertebral body, often accompanied by areas of cortical interruption and soft tissue extension, causing compression of the spinal cord or nerve roots. These lesions typically encompass the entire vertebral body, extend into the neural arch, expand the osseous margins, and include a component of soft tissue.” Tagged RBC SPECT/CT is a useful modality to avoid unnecessary biopsies or further investigations. Early phase SPECT/CT usually show intense uptake with absent to low grade uptake in the delayed phase.

☢️ Axillary soft tissue abscess ☢️ in a lymphoma patient following lymph node biopsy. FDG PET/CT scan shows cytic fluid collection with gas locules and hypermetabolic rim of intense FDG uptake, associated with axillary fat stranding and mild axillary skin thickening. There are also pathological enlarged lymph nodes Fluid aspiration confirmed Staphylococcus aureus as the causative agent.
🗓 Soft tissue abscess can be muscular, subcutaneous within the fascial planes. Risk factors include diabetics, immunosuppression, alcohol and intravenous drug use, traumatic/iatrogenic, remote infection. Clinical presentation vary according to the location and includes swelling, redness, and tenderness. Inflammatory markers are elevated usually elevated with intermittent fever.