[68Ga]Ga-PSMA-11 uptake in planepitheliale lung cancer: a pitfall in prostate cancer imaging.

Prostate cancer (PCa) is the second most frequent cancer diagnosis made in men and the fifth leading cause of death worldwide [1]. Prostate-specific membrane antigen labeled with gallium 68 ([68Ga]GaPSMA-11) is a promising radiotracer frequently used in diagnostics of the patients with biochemical recurrence of PCa. PSMA’s expression in non-small cell lung cancer (NSCLC) ranks around 16 %, while tumor neovasculature expression is seen in 59% of tumor samples and is dependent on NSCLC histopathological type. The highest (71%) is seen in large cell carcinoma (LCC) and in squamous cell carcinoma (SCC) – 64%, while the lowest (45%) is noted in adenocarcinoma (AC) [2, 3]. A 77-year-old man with prostate adenocarcinoma, Gleason 7 (3 + 4), TNM T2bNxM0, during hormonotherapy and urothelial carcinoma (T1bNxM0) during BCG therapy, was referred to [68Ga]GaPSMA-11 PET/CT study due to biochemical recurrence (total prostate specific antigen (t-PSA) 0.449 ng/ml). A cystoscopy performed one week before PET/CT examination was clear. The [68Ga]Ga-PSMA-11 showed an increased focal PSMA ligand uptake at the right side of the small pelvis (SUVmaxlbm up to 9.2, ▶ Fig. 1A), lump in segment 6 of the right lung (SUVmaxlbm up to 2.4, ▶ Fig. 1B) and area of parenchyma consolidation in segment 10 of the right lung (SUVmaxlbm up to 2.6, ▶ Fig. 1C). Moreover, [68Ga]Ga-PSMA-11 also revealed areas of pathological osteosclerotic remodeling in both hip bones and in both pubic bones without increased PSMA uptake. Patient underwent a resection of a lump (segment 6) in the right lung which revealed planoepitheliale lung cancer G3, pT1R0L1V1. Three months after resection, patient was referred to [18F]FDG PET/CT study which revealed (shown earlier in [68Ga]Ga-PSMA-11) tumor in segment 10 of the right lung (50 × 38 mm, SUVmaxlbm up to 12.3, ▶ Fig. 1D), branch of the diaphragm lymph node (18 × 20mm, SUVmaxlbm up to 5.8) and metastatic lesion in III right rib. Other changes in bones did not show any pathological uptake. Patient because of the comorbidities, age and extension of the disease was treated with palliative radiotherapy of the lung. A 69-year-old man t-PSA level 2.47 [ng/ mL], after prostatectomy followed by radiotherapy of regional lymph nodes and complementary hormonotherapy in 2007, currently under palliative hormonotherapy underwent [68Ga]Ga-PSMA-11 PET/CT study because of biochemical recurrence. The scan revealed a focal PSMA ligand uptake in the small pelvis (SUVmaxlbm up to 3.6), in enlarged right hilar lymph node SUVmaxlbm up to 2.7 (▶ Fig. 2A) and a soft-tissue lesion in left lung lower lobe (▶ Fig. 2B) with SUVmaxlbm up to 2.0. Patient a few months after [68Ga]Ga-PSMA11 PET/CT underwent a computed tomography (CT) examination of a thorax which showed right upper lobe mass extending round the main bronchus and involving hilar lymph nodes (▶ Fig. 2C). The soft-tissue lesion in the left lung lower lobe was less consolidated and more irregular in shape with a small cavity, probably due to necrosis (▶ Fig. 2D). Because of the suspicion of lung spread of PCa (even thus decreasing PSA level from 2.47 [ng/mL] to 1.75 [ng/mL]), bronchofiberscopy was performed (BFS). Histopathology results showed an invasive planoepitheliale akeratodes lung cancer: PD40(+), CK5/6(+), CKHMW(+), AMACR(+), TTF1(–), CK7(–), CK20(–), PSA(–), PSAP(–). Several authors reported an [68Ga]GaPSMA-11 uptake in lung adenocarcinoma [4, 5]. We showed an increased PSMA ligand uptake in 11 R section lymph node. Based on further medical history of the patient, dynamic lung invasion seen on CT images and decreasing PSA level during ▶ Fig. 1 Increased focal PSMA uptake at the right side of the small pelvis (A), lump in segment 6 of the right lung (B) and area of parenchyma consolidation in segment 10 of the right lung (C). FDG uptake in the segment 10 of right lobe (D). Case Report