Micronodular thymoma with lymphoid stroma: a clinicopathological study of five cases

GTF2I mutation in micronodular thymoma with lymphoid stroma

AIMS

Micronodular thymoma with lymphoid stroma is a rare subtype of thymoma with characteristic clinical and pathological features. Some of the features, such as indolent nature, principally spindle morphology and no significant association to myasthenia gravis, are shared with type A and AB thymoma, which is closely linked to GTF2I mutation. However, not much is known regarding the molecular genetics of this thymoma subtype. In this study, the GTF2I mutation status was investigated in 16 cases of micronodular thymoma.

METHODS

16 micronodular thymomas were retrieved and the GTF2I mutation was tested by Sanger sequencing. The clinicopathological findings were documented.

RESULTS

GTF2I c.1271T>A p.(Leu424His) mutation within exon 15 was detected in 14 out of 16 tumours (87.5%). Two patients died of other causes while all others remained alive with no evidence of recurrence during the follow-up period ranging from 19 to 188 months (median: 100 months).

CONCLUSIONS

GTF2I mutation status and presence of spindle cell morphology may indicate that type A and AB thymoma, and micronodular thymoma represent a group biologically distinct from type B thymomas, which generally lack this mutation.

Micronodular thymoma with lymphoid stroma: Contrast-enhanced CT features with histopathological correlation in 10 patients

Objectives

This study aimed to evaluate and summarize the contrast-enhanced computed tomography (CECT) imaging features of micronodular thymoma with lymphoid stroma (MTWLS) based on all MTWLS patients at our institution and was the first imaging study of MTWLS worldwide.

Methods

This retrospective study included 10 MTWLS patients who underwent CECT between April 2012 and November 2021. We collected and analyzed the CECT imaging features, including the location, size, shape, tumor density, classification, and CT value of the solid component. Descriptive statistical analysis was performed using the SPSS software (version 26.0; IBM).

Results

Ten patients (five males [50%], five females [50%]; median age, 61.4 years; range, 54-72 years) underwent CECT. Of the 10 cases, one case was purely cystic, seven cases were cystic-solid, and two cases were purely solid. Six cases were round/oval in shape, and four cases were irregularly shaped. Excluding a purely cystic tumor with an unmeasurable degree of enhancement, two cases showed moderate enhancement, and seven cases showed significant enhancement. Among the solid or cystic-solid cases, the mean CT value of the measurable solid component on the enhanced scan was 93.9 HU. Nine masses were located adjacent to the mediastinal pleura, pericardium, or large vessels. Additionally, there were no malignant tumor signs in any patient, including penetration of the mediastinal pleura or involvement of the pericardium, pleural effusion, elevation of the diaphragm, or direct vascular invasion.

Conclusion

MTWLS demonstrates certain features on CECT, such as a high rate of cystic change, significant solid component enhancement, and no malignant, invasive imaging features. These CECT features are helpful for diagnosing MTWLS.