Detection of Unknown Primary Tumors Using Whole Body FDG PET

Objective: To assess the usefulness of 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) in locating occult primary lesions. Methods: 50 patients with varying heterogeneous metastases of unknown primary origin were referred for FDG PET. The locations of the known metastatic tumor manifestations were distributed as follows: cervical lymph nodes metastases (n=18), skeletal metastases (n=15), cerebral metastases (n=12), others (n=5). All patients underwent whole body ^(18)F-FDG PET imaging. The images were interpreted by visual inspection and semi-quantitative analysis (standardized uptake value, SUV). The patients had undergone conventional imaging within 2 weeks of FDG PET. Surgical, clinical and histopathologic findings were used to assess the performance of FDG PET. Results: FDG PET was able to detect the location of the primary tumor in 32/50 patients (64%). The primary tumors were proved by histopathologic results, and located in the lungs (n=17), the nasopharynx (n=9), the breast (n=2), the ovary (n=1), the colon(n=1), the prostate(n=1),the thyroid (n=1). FDG PET were proved false positive in 2 patients (4%), and the suspicious primary tumors were in uterus and colon respectively. During the clinical follow-up of 2 to 26 months, the primary tumor was found in only 2 patients (prostate cancer, gastric cancer). Conclusion: PET imaging allows identification of the primary site and metastatic lesions(including bone and soft tissue metastases) at a single examination. Whole body ^(18)F-FDG PET allows effective localization of the unknown primary site of origin and can contribute substantially to patient care.

Primary ascending colon cancer accompanying skip metastases in left shoulder skin and left neck lymph node: A case report

BACKGROUND Lymph node skip metastases are common in lung,breast,and thyroid cancer patients,but are rare in colon cancer patients.Specifically,lymph node skip metastases occur in 1%-3%of colon cancer patients.Previous reports have demonstrated colon cancer skip metastases involving the retropancreatic and portocaval lymph nodes and Virchow's node;however,reports involving skip metastases into the left neck lymph nodes and left shoulder skin are extremely rare,as are related reports of clinical treatment and prognosis.CASE SUMMARY A 44-year-old Chinese man was admitted to the hospital for evaluation of persistent shoulder pain for 3 d and a cutaneous mass(3.0 cm×2.0 cm)on the left shoulder.The left shoulder cutaneous mass was excised and bisected,revealing tissues with a fish-like appearance.The pathologic diagnosis of the cutaneous mass suggested a signature[CDX-2(++),CK20(++),Ki-67(+)>50%]of infiltrating or metastatic colorectal adenocarcinoma.An enhanced computed tomography scan of the abdomen revealed chronic appendicitis with fecal stone formation,cecal edema,and a pelvic effusion.A colonoscopy revealed a cauliflower-like mass within the ascending colon area that involved the lumen.The surface of the ascending colon mass was eroded and bleeding;a biopsy was performed.The pathologic diagnosis of the colonoscopy biopsy was an ascending colon mucinous adenocarcinoma.The patient underwent a laparoscopic radical resection of the right colon based on the pathological diagnosis.The tumor was 5.0 cm×4.5 cm×1.8 cm in size and infiltrated the entire thickness of the intestinal wall with vascular tumor thrombi.No nerve tissue involvement was noted.The ileum and colon resection margins were negative.The postoperative pathologic analysis revealed non-metastatic involvement of ileocecal,pericolic,or peri-ileal lymph nodes.The postoperative medical examination revealed palpably enlarged lymph nodes in the left neck,and the following color Doppler ultrasound examination of the neck confirmed enlarged lymph nodes in the left neck.After surgical resection and pathologic diagnosis,a common pathologic signature consistent with resected cutaneous mass and right colon was identified,suggesting skip metastasis of left cervical lymph nodes.The patient was then treated with eight courses of chemotherapy and under followup evaluations for 4 years;currently,no tumor recurrences or metastases have been noted.CONCLUSION We report an abnormal skip metastasis involving the left shoulder skin and left neck lymph node in a patient with ascending colon adenocarcinoma.Specifically,we observed non-metastatic involvement of the lymph nodes around the tumor site but with metastases to the cervical lymph nodes.The standard surgical operations were performed to resect the cutaneous mass,tumor tissue,and cervical lymph nodes,followed by chemotherapy for eight courses.The patient is healthy with no tumor recurrences or metastases for 4 years.This clinical case will contribute to future research about the abnormal skip metastasis in colon cancers and a better clinical treatment design.

Malignant Peripheral Nerve Sheath Tumor of the Thigh Invading the Superficial Femoral Artery, with Necrotic Lung Metastases as Presenting Symptoms

A NF1 (neurofibromatosis 1) patient developed multiple necrotic lung metastases from a sciatic malignant peripheral nerve sheath tumor (MPNST) invading the superficial femoral artery. The first diagnosis was metastases of a non-small-cell adenocarcinoma because the right calf MPNST was not clinically noticeable ant that the chest/abdomen PET/CT did not include the region of the legs. When the MPNST was diagnosed, new histological analysis on the metastases changed the diagnosis to that of epithelioid undifferentiated sarcoma. The article deals with the sometimes-delayed diagnosis in those NF1 patients with large palpable masses and chronic pain pre-existing the malignant transformation, and discusses the difficulty of the biopsy of necrotic metastases.