PMC6702522_01
Initial and follow-up FDG PET/CT: (A) Initial FDG-MIP with multiple hypermetabolic lesions in the upper lobe of the right lung, in mediastinal, hilar and upper mesenteric lymph nodes and at the left pleura. Increased turnover of the bone marrow. (B) Initial fusion FDG-PET/CT axial slice with pathologic high FDG-uptake in the left pleura, upper mesenteric lymph nodes, and bone marrow. Normal presentation of liver, spleen, and stomach. (C) Follow-up FDG-MIP after 4 months on pembrolizumab shows a generally reduced metabolism at all tumor locations. Normalization of the bone marrow turnover. Due to newly incipient traumatic injury at the left shoulder the patient could not lift up the left arm. (D) Fusion FDG-PET/CT axial slice after 4 months on pembrolizumab with residual FDG-uptake at the left pleura and in upper mesenteric lymph nodes. Normal presentation of the bone marrow. (E) Follow-up FDG-MIP after 11 months on pembrolizumab shows further regression of lesions in the upper lobe of the right lung as well as in mediastinal, hilar, and upper mesenteric lymph nodes (the focal lesions in the left mediastinum and supraclavicular right represent the central venous catheter). Residual focal FDG-Uptake in the left pleura. Normal turnover of the bone marrow. (F) Fusion FDG-PET/CT axial slice after 11 months on pembrolizumab with only little elevated FDG-uptake in the left pleura. The formerly upper mesenteric lymph node is healed up. Normal presentation of liver, spleen, stomach, and bone marrow.
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F1
An FDG PET/CT scan confirmed these findings, and the scan revealed a hypermetabolic activity in mesenteric lymph nodes and at the left pleura (Figures 1A,B). PET/CT study showed a partial remission with a moderate morphologic reduction of the tumor load, but a markedly reduced metabolic activity at all tumor sites (Figures 1C,D). Pembrolizumab treatment continued at a dose of 200 mg IV every 3 weeks. Residual focal FDG-Uptake was seen in the left pleura (Figures 1E,F).
Histomorphological and immunohistochemical analysis of parietal pleura, biopsy from 2018: (A) H & E staining, (B) Immunostaining for CD5, (C) Immunostaining for CD117, and (D) Immunostaining for PD-L1.
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F2
Surprisingly, histopathological examination revealed a non-small cell carcinoma (Figure 2A) expressing CD5 (Figure 2B), CD117 (Figure 2C), and p63 all indicating a carcinoma of thymic origin. Anticancer immunity and potential response to immunotherapy were assessed by PD-L1 staining of the pleural tumor, which showed a high expression level of 60% (Figure 2D).
Histomorphological and immunohistochemical analysis of parotid, tumor excisate from 2008: (A) H & E staining, (B) Immunostaining for CD5, and (C) Immunostaining for CD117.
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F3
With no signs of a thymic pathology, the histopathological diagnosis of CASTLE was established, and as additional immunostainings for CD5 (Figure 3B) and CD117 (Figure 3C) in the specimen of the parotid cancer diagnosed 2008 were positive also, a rare case of a CASTLE tumor of the parotid healed at the primary and neck sites, but with late metastatic dissemination was diagnosed.