Comparative genetic analysis of a rare synchronous collision tumor composed of malignant pleural mesothelioma and primary pulmonary adenocarcinoma

Identification of Novel Diagnostic Markers for Malignant Pleural Mesothelioma Using a Reverse Translational Approach Based on a Rare Synchronous Tumor

Although the routine use of immunohistochemistry has improved the accuracy of histopathologic diagnosis in clinical practice, new methods for discovering novel diagnostic markers are still needed. We sought new diagnostic markers for malignant pleural mesothelioma (MPM) using a reverse translational approach with limited archival tissues from a very rare case. Total RNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues of a synchronous collision tumor consisting of MPM and pulmonary adenocarcinoma (PAC) was employed for gene expression profiling (GEP) analysis. Among the 54 genes selected by GEP analysis, we finally identified the following two candidate MPM marker genes: PHGDH and TRIM29. Immunohistochemical analysis of 48 MM and 20 PAC cases showed that both PHGDH and TRIM29 had sensitivity and specificity almost equivalent to those of calretinin (sensitivity 50% and 46% vs. 63%, and specificity 95% and 100% vs. 100%, respectively). Importantly, of the 23 epithelioid MMs, all 3 calretinin-negative cases were positive for TRIM29. These two markers may be diagnostically useful for immunohistochemical distinction between MPMs and PACs. This successful reverse translational approach based on FFPE samples from one very rare case encourages the further use of such samples for the development of novel diagnostic markers.

Tumor Biology is King: Secondary Tumors of the Thyroid From 2 Medical Centers in China

BACKGROUND

We studied the clinical characteristics, diagnosis, treatment, and prognosis of secondary tumors of the thyroid (STTs) and analyzed this rare phenomenon based on our clinical experience.

METHODS

We reviewed 16 000 malignant thyroid tumors diagnosed at 2 medical centers in China from 1978 to 2018, including 55 patients with STTs.

RESULTS

The most frequent primary tumor sites included lung (21.8%), gastrointestinal (18.2%), breast (14.5%), and kidney (12.7%). The median age at STT diagnosis was 56 years. The time from diagnosis of primary tumor to metastases to the thyroid ranged from 0 to 108 months, with the longest interval being for renal cell carcinoma (RCC; mean: 49 months). There were 22 cases of single metastatic foci and 33 cases of multiple metastatic foci. At the time of STT diagnosis, 42 patients had multiple organ metastases and 13 patients had only thyroid metastases. Thyroid function was examined in 50 patients, including 23 with Hashimoto's thyroiditis. Metastases were diagnosed histologically and confirmed by negative immunohistochemistry for thyroid markers. Twenty-one patients were treated with resection, including total thyroidectomy in 14 and unilateral lobectomy in 7. Thirty-four patients were treated without resection, but 2 were treated with tracheotomy. The median survival time of all patients with metastasis was 10 months (range: 1-96 months). Patients with primary RCC had the best prognosis (median survival time: 52 months), followed by patients with breast cancer (33 months). Patients who underwent thyroid surgery had a better prognosis than patients without thyroid surgery. Patients with single metastatic foci or single organ metastases had a better prognosis than patients with multiple metastatic foci or multiple organ metastases.

CONCLUSIONS

Metastasis to the thyroid is a rare clinical phenomenon, and sometimes a diagnosis of STT is difficult; so, we need to pay more attention to it. While prognosis appears to be related to surgery or some characteristics of metastatic spread, these data suggest it is more complex. Tumor biology is king; in fact, prognosis was mainly related to the biological behavior of the primary tumor. We cannot only opt for surgery; thus, case selection is important, and the treatment strategy for STT patients should be determined individually according to their specific biological behaviors.