Putative lung adenocarcinoma with epidermal growth factor receptor mutation presenting as carcinoma of unknown primary site: A case report

Magnetic resonance imaging and 18F-fludeoxyglucose positron emission tomography/computed tomography findings of retroperitoneal clear cell carcinoma with an unknown primary site: A case report

Herein, we report a case of retroperitoneal clear cell carcinoma (RCCC) with an unknown primary site that was confirmed via pathology. A 46-year-old man presented with low-grade fever, hyperhidrosis, and nightly fatigue that had occurred for the last 20 days. His weight had decreased significantly within the past 2 months (approximately 12 kg). On abdominal ultrasound, a mass was observed near the left renal hilum. In addition, enhanced magnetic resonance imaging (MRI) of the abdomen revealed a retroperitoneal nodular mass; however, no abnormalities in either kidney or adrenal glands were observed. 18F-fludeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) demonstrated an intensely FDG-avid retroperitoneal mass, the maximum standardized uptake value (SUVmax) was 19.6. On March 8, 2021, left retroperitoneal lesion resection, retroperitoneal lymph node dissection, and double kidney exploration were performed under general anesthesia. A post-operative pathological examination revealed Poorly differentiated clear cell carcinoma (left retroperitoneal) and metastatic lymph nodes. Immunohistochemical findings showed that the tumor originated from the kidney. At 6-month follow-up, reexamination of the patient revealed retroperitoneal lesion recurrence; however, no abnormalities were observable via enhanced computed tomography (CT) of both kidneys. To our knowledge, there have been no previous reports of RCCC of unknown origin.

Cancer of Unknown Primary in the Molecular Era

Cancer of unknown primary (CUP) is a rare malignancy that presents with metastatic disease and no identifiable site of origin. Most patients have unfavorable features and attempts to treat based on tissue-of-origin identification have not yielded a survival advantage compared with empiric chemotherapy. Next-generation sequencing has revealed genomic alterations that can be targeted in selected cases, suggesting that CUP represents a unique malignancy in which the genomic aberrations may be integral to the diagnosis. Recent trials focusing on tailored combination therapy matched to the genomic alterations in each cancer are providing new avenues of clinical investigation. Here, we discuss recent findings on molecular aberrations in CUP and how the genomic and immune landscape can be leveraged to optimize therapy.

Brain Metastasis from Unknown Primary Tumour: Moving from Old Retrospective Studies to Clinical Trials on Targeted Agents

Simple Summary

Brain metastases (BMs) are the most common intracranial tumours in adults and occur up to 3–10 times more frequently than primary brain tumours. In up to 15% of patients with BM, the primary tumour cannot be identified. These cases are known as BM of cancer of unknown primary (CUP) (BM-CUP). The understanding of BM-CUP, despite its relative frequency and unfavourable outcome, is still incomplete and clear indications on management are missing. The aim of this review is to summarize current evidence on the diagnosis and treatment of BM-CUP.

Abstract

Brain metastases (BMs) are the most common intracranial tumours in adults and occur up to 3–10 times more frequently than primary brain tumours. BMs may be the cause of the neurological presenting symptoms in patients with otherwise previously undiagnosed cancer. In up to 15% of patients with BMs, the primary tumour cannot be identified. These cases are known as BM of cancer of unknown primary (CUP) (BM-CUP). CUP has an early and aggressive metastatic spread, poor response to chemotherapy, and poor prognosis. The pathogenesis of CUP seems to be characterized by a specific underlying pro-metastatic signature. The understanding of BM-CUP, despite its relative frequency and unfavourable outcome, is still incomplete and clear indications on management are missing. Advances in diagnostic tools, molecular characterization, and target therapy have shifted the paradigm in the approach to metastasis from CUP: while earlier studies stressed the importance of finding the primary tumour and deciding on treatment based on the primary diagnosis, most recent studies focus on the importance of identifying targetable molecular markers in the metastasis itself. The aim of this review is to summarize current evidence on BM-CUP, from the diagnosis and pathogenesis to the treatment, with a focus on available studies and ongoing clinical trials.

"Metastatic Cancer of Unknown Primary" or "Primary Metastatic Cancer"?

Cancer of unknown primary (CUP) is an umbrella term used to classify a heterogeneous group of metastatic cancers based on the absence of an identifiable primary tumor. Clinically, CUPs are characterized by a set of distinct features comprising early metastatic dissemination in an atypical pattern, an aggressive clinical course, poor response to empiric chemotherapy and, consequently, a short life expectancy. Two opposing strategies to change the dismal prognosis for the better are pursued. On the one hand, following the traditional tissue-gnostic approach, more and more sophisticated tissue-of-origin (TOO) classifier assays are employed to push identification of the putative primary to its limits with the clear intent of allowing tumor-site specific treatment. However, robust evidence supporting its routine clinical use is still lacking, notably with two recent randomized clinical trials failing to show a patient benefit of TOO-prediction based site-specific treatment over empiric chemotherapy in CUP. On the other hand, with regards to a tissue-agnostic strategy, precision medicine approaches targeting actionable genomic alterations have already transformed the treatment for many known tumor types. Yet, an unmet need remains for well-designed clinical trials to scrutinize its potential role in CUP beyond anecdotal case reports. In the absence of practice changing results, we believe that the emphasis on finding the presumed unknown primary tumor at all costs, implicit in the term CUP, has biased recent research in the field. Focusing on the distinct clinical features shared by all CUPs, we advocate adopting the term primary metastatic cancer (PMC) to denominate a distinct cancer entity instead. In our view, PMC should be considered the archetype of metastatic disease and as such, despite accounting for a mere 2–3% of malignancies, unraveling the mechanisms at play goes beyond improving the prognosis of patients with PMC and promises to greatly enhance our understanding of the metastatic process and carcinogenesis across all cancer types.

ROS1-rearranged putative lung adenocarcinoma presenting as carcinoma of unknown primary site: a case report

Carcinoma of unknown primary site (CUP) is diagnosed only in 2-9% of all cancer cases. Adenocarcinomas account for approximately 60% of CUP, and some of these are putative lung adenocarcinomas. The frequency of driver oncogene positivity in the putative lung adenocarcinomas is unknown, and the efficacy of targeting therapies for the driver oncogene is also unknown. This is the first case report of C-ros oncogene 1 (ROS1)-rearranged putative lung adenocarcinoma presenting as CUP showing a good response to ROS1 inhibitor therapy. A 55-year-old woman presented with neck lymphadenopathy. Computed tomography and [18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) showed swelling of the bilateral supraclavicular, left accessory, mediastinal, and abdominal lymph nodes. The pathological analysis of the lymph node specimen biopsy indicated adenocarcinoma with cytokeratin 7 and thyroid transcription factor-1 positivity. Thus, this case was identified as ROS1- rearranged putative lung adenocarcinoma presenting as CUP. Oral crizotinib, an ROS1 inhibitor, was administered at a dose of 250 mg twice daily. Four weeks later, several swollen nodes showed marked improvement, and eight weeks later, FDG PET showed almost no uptake. In conclusion, putative lung adenocarcinoma presenting as CUP may involve ROS1 rearrangement, and ROS1 inhibitor therapy may be effective.

Lymph node cancer of the mediastinum with a putative necrotic primary lesion in the lung: a case report

Background

Although mediastinal lymph node cancer is presumed to originate in the lung, the primary site is usually unidentified, so the pathological course remains unclear. We recently encountered a case of mediastinal lymph node cancer having a putative primary lesion remaining in the lung as a necrotic focus.

Case presentation

The patient was a 56-year-old man who visited our department because computed tomography screening had revealed a nodular shadow in the lingular segment. However, on positron emission tomography, fluorine-18 deoxyglucose accumulation was detected in a subcarinal lymph node and not in the nodule in the lingular segment. Biopsy of the lung tumor and the lymph node was performed via minimal thoracotomy. Intraoperative pathologic examination showed necrosis alone and no malignant findings in the lung tumor. By contrast, carcinoma was detected in the lymph node. Additional subcarinal lymph node dissection was performed. Results of postoperative histopathologic examination indicated poorly differentiated adenocarcinoma of the subcarinal lymph node. Meanwhile, the nodule in the lingular segment was speculated to be a spontaneously resolved primary focus of lung cancer.

Conclusions

In this case, the primary lung cancer focus resolved spontaneously after lymph node metastasis, explaining the pathogenesis underlying mediastinal lymph node cancer of unknown primary site. For similar cases of malignancy, aggressive treatment, including surgery, is effective.