Lung Cancer Detected 5 Years after Resection of Cancer of Unknown Primary in a Mediastinal Lymph Node: A Case Report and Review of Relevant Cases from the Literature

Abstract

We report the rare and interesting case of a primary lung cancer detected 5 years after cancer of unknown primary (CUP) of a mediastinal lymph node (LN) was resected. A 40-year-old male was diagnosed with adenocarcinoma of unknown primary in a mediastinal lymph node after resection of the mediastinal tumor. Five years after resection of the CUP in mediastinal LN, a small, abnormal nodular shadow in left upper lobe was detected by chest CT. This pulmonary tumor was diagnosed as a lung adenocarcinoma. The pathological and immunohistological findings of the resected pulmonary tumor resembled those of the LN resected 5 years before. We speculated that the pulmonary lesion represented primary lung cancer that enlarged later than the metastatic mediastinal LN. This case illustrates the importance of careful observation and long-term follow-up in patients treated for CUP of a thoracic LN.

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

“…A possible pathogenesis of lymph node CUP is a small primary focus that cannot be detected with diagnostic imaging [ 3 ] or spontaneous resolution of the primary focus [ 10 , 11 ]. Some immunologic mechanisms may be involved in the spontaneous resolution of the primary focus [ 11 , 12 ].…”

“…In general, CUP prognosis is poor, with a median survival period of 2–9 months and a 5-year survival rate of 2.8–6.0% [ 2 , 8 ]. Meanwhile, mediastinal lymph node CUP follows a clinical course different from that of CUP in general, and the prognosis is favorable when the localized focus in the lymph node is resected [ 3 , 5 , 16 ]. In cases of mediastinal lymph node enlargement, a surgical approach should be considered for both diagnostic and therapeutic purposes, even if the primary focus cannot be identified.…”

“…Recently published case reports regarding cancer of the intrathoracic lymph nodes were reviewed [ 3 , 4 , 16 – 25 ]. The patient characteristics of all 18 cases (including our case) are shown in Table 1 .…”

“…Completely resected mediastinal lymph node CUP reportedly has a better prognosis than lung cancer with mediastinal lymph node metastasis [ 4 , 10 ]. Complete resection is the first-line treatment if the lesion of the lymph node cancer of the hilum or mediastinum is localized [ 3 , 5 , 16 ]. Although the lung is highly likely to be the primary site of metastatic mediastinal lymph node cancer, lobectomy is generally avoided to preserve respiratory function.…”

“…Cancer of unknown primary site (CUP) rarely occurs in the mediastinal lymph node, and its underlying pathology is typically not elucidated [ 1 , 2 ]. Many cases of mediastinal lymph node cancer are presumed to arise from the lung, but the primary focus remains essentially unidentified at the time of diagnosis [ 1 , 3 – 5 ]. Although patients are usually treated by chemoradiation therapy or surgery, no standard treatment has been established.…”