PET/CT-Guided Biopsy in Necrotic Lung Mass: A Diagnostic Breakthrough

A 60-year-old male who never smoked presented with a 2-month history of dull, poorly localized right-sided chest pain and a dry cough. He also reported a loss of appetite and unintentional weight loss. On clinical examination, he was hemodynamically stable, with clear breath sounds bilaterally. His hemogram and biochemical parameters were within normal limits, and electrocardiography showed a normal sinus rhythm.

A posteroanterior chest radiograph revealed a suspicious mass lesion in the right upper zone. Contrast-enhanced computed tomography (CT) of the chest demonstrated a 70 mm × 40 mm × 61 mm spiculated, heterogeneously enhancing soft-tissue lesion in the apical segment of the right upper lobe. Whole-body ¹⁸F-fluorodeoxyglucose positron/emission tomography (FDG PET) showed avid uptake in the lesion (maximum standardized uptake value, 8.4), suggesting high metabolic activity consistent with malignancy.

Radial endobronchial ultrasound (EBUS)-guided transbronchial lung biopsy was performed. Fiberoptic bronchoscopy showed no visible endobronchial growth. Biopsy specimens obtained under radial EBUS guidance yielded inconclusive histopathologic findings. A follow-up CT-guided percutaneous biopsy of the mass demonstrated necrotic material only, without viable tumor cells.

The imaging features and metabolic activity were strongly suggestive of malignancy, yet repeated biopsy attempts by various conventional methods failed to yield diagnostic tissue.

A robot-assisted FDG PET-/CT-guided biopsy was planned, and the procedure was attempted to precisely target the highest metabolic area of the lung mass lesion. Adequate sample cores were extracted, and the final histopathology confirmed the diagnosis of adenocarcinoma lung [Figures 1-5].

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Figure 1 Axial computed tomography (CT) image (a) showing a heterogeneously enhancing soft-tissue lesion with spiculated margins in the apical segment of the right upper lobe. Axial fluorodeoxyglucose (FDG) positron-emission tomography CT fusion image (b) reveals intense FDG uptake (SUVmax 8.4) in the lesion, indicating high metabolic activity only in the peripheral areas with central necrotic hypometabolic area. These imaging findings are consistent with a malignant neoplasm. However, both radial endobronchial ultrasound-guided and CT-guided biopsies yielded nondiagnostic specimens consisting of necrotic material only

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Figure 2 (a) The lung lesion seen in fluorodeoxyglucose positron-emission tomography computed tomography (PET/CT) had striking feature of high metabolic activity in the periphery with a large area of hypometabolism and necrosis in center. A robot-assisted PET-/CT-guided mapping was done to target only the hypermetabolic region of the lesion. The following parameters were planned during the PET-/CT-guided procedure: Patient position: prone. Approach: from back. Target depth: 40 mm. Orbital angle: 14.92°. Craniocaudal angle (C/C): 0.00°. (b) Multiple tissue cores extracted largest 1 cm long from the high metabolic areas

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Figure 3 Histopathology: Adenocarcinoma. (a) These atypical cells show immunopositivity for CK7 (cytoplasmic positivity). (b) The tumor cells are positive for TTF1 while negative for p40, diagnosed as a case of adenocarcinoma

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Figure 4 Computed tomography (CT)-guided biopsy: Necrotic cores. (a) CT-guided lung biopsy showing only necrotic cores. (b) No viable cells seen

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Figure 5 Positron-emission tomography (PET)-guided biopsy. (a) PET-guided lung biopsy one necrotic core and other core showing atypical cells (highlighted by arrow). (b) Atypical cells seen in the glandular pattern

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The case underscores the diagnostic difficulty in sampling centrally necrotic tumors and the need for integrating PET/CT imaging with clinical and histologic correlation.

Several studies have highlighted the diagnostic challenges in obtaining representative tissue from centrally necrotic or metabolically heterogeneous lung tumors. In such cases, conventional biopsy methods such as CT-guided percutaneous biopsy or transbronchial lung biopsy often yield necrotic or nondiagnostic material, as observed in our patient.[12] FDG PET/CT has been reported to play a pivotal role in guiding biopsies by identifying the most metabolically active viable tumor regions, thereby improving diagnostic yield.[34] Unlike previous reports that mainly describe FDG PET-/CT-assisted localization followed by CT-guided biopsy, our case demonstrates the successful application of robot-assisted FDG PET-/CT-guided biopsy, which allowed precise sampling of the metabolically active portion of the lesion and ultimately established the diagnosis of lung adenocarcinoma. This highlights a potential advantage of integrating robotic navigation with metabolic imaging to overcome limitations of conventional approaches.