Understanding and Overcoming the Pitfalls in Cytopathological Diagnosis of Hyalinizing Trabecular Tumor of Thyroid.

Hyalinizing trabecular tumor (HTT), a rare low-malignant-potential thyroid neoplasm, is usually treated with conservative surgery. However, cytomorphological diagnosis of HTT is challenging due to the significant overlap of nuclear features with more common malignancies such as papillary thyroid carcinoma (PTC), which usually requires more radical surgical intervention. To avoid unnecessary overtreatment, a precise diagnosis of HTT is therefore essential. Advances in molecular diagnostics provide the opportunity to overcome the limitations of cytological analysis. We present a case of HTT in a 71-year-old male who was initially suspected to be PTC based on cytopathology. However, further molecular analysis revealed PAX8::GLIS3 gene fusion, classifying the lesion as HTT and preventing surgical overtreatment. We discuss the diagnostic pitfall of cytopathology in HTT and suggest using emerging molecular genetic tools to avoid it.

Diagnostic difficulties in non-tuberculous mycobacterial infection in lung transplant recipients.

Despite antimicrobial prophylaxis, 34% to 59% of lung transplant recipients experience severe life-threatening opportunistic infections, sometimes caused by Nontuberculous Mycobacteria (NTM) and Nocardia. Although differentiating these infections is of utmost importance for effective treatment, it can be challenging as they share morphological and growth characteristics. Therefore, culture remains the gold standard for laboratory confirmation. With the aid of novel molecular methods performed on the cultured organisms, diagnosis may be accomplished rapidly and precisely. We present a case of a lung transplant recipient with a pulmonary infection where long, thin, beaded, branching filamentous organisms were seen with Acid-Fast Bacilli (AFB) and Modified Gomori's Methenamine Silver (GMS) stains in bronchoalveolar lavage sample. Cytological characteristics led to the suspicion of a Nocardia species infection. However, culture and the PCR-restriction fragment length polymorphism analysis (PRA) identified M. fortuitum. Additionally, antibiotic resistance was detected, which aided in choosing the appropriate treatment. Therefore, to overcome such diagnostic difficulties to differentiate NTM and Nocardia, a multidisciplinary approach including culture, molecular methods, and cytology is needed to enhance clinical outcomes.