Indian Journal of Nuclear Medicine

INTERESTING IMAGE
Year
: 2020  |  Volume : 35  |  Issue : 3  |  Page : 241--243

Coexisting somatostatin receptor expressing gastric neuroendocrine tumor primary and lymph nodal tuberculosis on 68Ga-DOTANOC positron emission tomography/computed tomography


Saurabh Arora1, Sameer Rastogi2, Shamim Ahmed Shamim1, Adarsh Wamanrao Barward3, Benjamin Leroy Passah4,  
1 Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India
2 Department of Medical Oncology, All India Institute of Medical Sciences, New Delhi, India
3 Department of Pathology, All India Institute of Medical Sciences, New Delhi, India
4 Department of Paediatric Surgery, Dr. Ram Manohar Lohia Hospital and Post Graduate Institute of Medical Sciences, New Delhi, India

Correspondence Address:
Dr. Shamim Ahmed Shamim
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi
India

Abstract

Gastric neuroendocrine tumors (G-NETs) express somatostatin receptors (SSTR), which can be imaged using radiolabeled somatostatin analogs, including 68Ga-DOTA octreotide analogs. SSTR expression is also seen in activated lymphocytes and macrophages, which might result in false-positive results on SSTR imaging, in patients with coexistent granulomatous pathologies including tuberculosis, sarcoidosis, and Wegener's granulomatosis. We present a case where 68Ga-DOTANOC positron emission tomography/computed tomography (PET/CT) showed primary G-NET, with SSTR expressing nonregional lymph nodes which on histopathology showed necrotizing granulomas with Langhans histiocytes. Antitubercular therapy was started, and a decrease in size and SSTR expression in involved lymph nodes was noted on follow-up 68Ga-DOTANOC PET/CT.



How to cite this article:
Arora S, Rastogi S, Shamim SA, Barward AW, Passah BL. Coexisting somatostatin receptor expressing gastric neuroendocrine tumor primary and lymph nodal tuberculosis on 68Ga-DOTANOC positron emission tomography/computed tomography.Indian J Nucl Med 2020;35:241-243


How to cite this URL:
Arora S, Rastogi S, Shamim SA, Barward AW, Passah BL. Coexisting somatostatin receptor expressing gastric neuroendocrine tumor primary and lymph nodal tuberculosis on 68Ga-DOTANOC positron emission tomography/computed tomography. Indian J Nucl Med [serial online] 2020 [cited 2021 Mar 2 ];35:241-243
Available from: https://www.ijnm.in/text.asp?2020/35/3/241/288460


Full Text



A 34-year-old man who presented with abdominal discomfort, decreased appetite, and weight loss on evaluation was found to have gastric polyps on endoscopy, elevated serum antiparietal cell antibody (titer 1:20), plasma chromogranin A level of 527 ng/ml (normal <76.3 ng/ml), and serum gastrin level of 977 pg/ml (13–115 pg/ml). He underwent 68 Ga-DOTANOC positron emission tomography/computed tomography (PET/CT) for the evaluation of gastric neuroendocrine tumor (G-NET). The scan [Figure 1] revealed somatostatin receptor (SSTR) expressing polypoidal lesion (maximum standardized uptake value [SUVmax]: 25.7) in gastric fundus [Figure 1]a, [Figure 1]b, [Figure 1]c, arrowhead] and also noted enlarged right paratracheal lymph nodes (SUVmax: 5.23) [Figure 1]d, [Figure 1]f, [Figure 1]g, white arrow]. Endoscopic biopsy of gastric lesion [Figure 2]a, [Figure 2]b, [Figure 2]c, [Figure 2]d shows small round cell tumor [Figure 2]a, with immunohistochemistry positive for synaptophysin [Figure 2]b, chromogranin [Figure 2]c, and Ki-67 index <1% [Figure 2]d, white arrow], suggesting well-differentiated neuroendocrine tumor (NET) (Grade 1). Histopathology of paratracheal lymph node revealed necrotizing epithelioid cell granulomatous inflammation with Langhans giant cell [Figure 2]e and [Figure 2]f, black arrows]. Considering the clinical, imaging, and node histopathology findings, the patient was started on antitubercular therapy. Follow-up 68 Ga-DOTANOC PG-NET done 3 months after starting antitubercular therapy (ATT) revealed a reduction in size and SSTR expression of previously involved lymph nodes [Figure 3]d, [Figure 3]e, [Figure 3]f, [Figure 3]g, white arrow] suggesting response to ATT and no significant interval change in gastric carcinoid [Figure 3]a, [Figure 3]b, [Figure 3]c, arrowhead].{Figure 1}{Figure 2}{Figure 3}

G-NET is classified into four clinical types. Type 1 is most common with a lower risk of lymph nodal and distant metastases resulting in good overall prognosis.[1],[2] Well-differentiated NET is known to express SSTR.[3] SSTR expression (68 Ga-DOTANOC uptake) can also be seen in granulomatous pathologies including tuberculosis (TB), fungal, bacterial, and protozoan infections and noninfectious diseases including sarcoidosis, Crohn's disease, and Wegener's granulomatosis.[4] In chronic inflammatory pathologies, including TB, this 68 Ga-DOTANOC avidity is due to the SSTR expression on activated lymphocytes and macrophages present in granulomas.[5] Although the presence of this uptake opens a window to image granulomatous pathologies as shown by Vanhagen et al., this might result in false-positive results in patients with NET having coexistent granulomatous pathologies; hence, the understanding of the false-positive sites is important for correct decision-making.[6] Sometimes, even after thorough histological examination and special stains, obvious infectious etiology resulting in granulomatous inflammation cannot be found, but Few histology features are suggestive of tuberculosis, such as granuloma formation by epithelioid histiocytes and Langhans type giant cells.[7],[8],[9] The diagnosis of extrapulmonary TB is sometimes difficult when bacteriological proof is lacking, but in areas with high prevalence like India (very high pretest probability), it can be assumed that granulomatous lymphadenitis is of tubercular origin after taking clinical and imaging features into consideration.[10],[11] Regarding the management of Type 1 G-NETs, endoscopic resection and follow-up is an acceptable treatment option.[12] In view of nonmetastatic Grade 1 gastric carcinoid in our patient, he is planned for endoscopic removal of gastric polyp and has shown good response to ATT for lymph node TB which was incidentally detected on 68 Ga-DOTANOC PET/CT.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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