FDG PET/CT imaging of extrapulmonary small cell carcinoma of the adrenal gland

A Unique Case of Poorly Differentiated Neuroendocrine Carcinoma With Brain and Bilateral Adrenal Metastases

BACKGROUND

Small-cell carcinoma is a highly malignant neuroendocrine neoplasm arising from cells of the endocrine and nervous systems, and usually of bronchogenic origin. When found in the retroperitoneum, these malignant cells are extremely rare and are mainly metastatic tumors. Adrenal glands are unusual sites of distant metastases, the common primary being bronchopulmonary and gastroenteropancreatic neuroendocrine tumors (NETs). We report a case of poorly differentiated neuroendocrine carcinoma (NEC) that was initially discovered in both adrenal glands.

CASE

Our patient was a 68-year-old woman who presented with articular pain and severe chronic hemolytic anemia. Her workup comprised a contrast-enhanced computed tomography (CT) scan of the chest, abdomen, and pelvis, revealing a left adrenal mass lesion measuring 14 × 9 cm, and a concomitantly smaller right adrenal mass lesion arising from the gland and measuring 4 × 2 cm. In view of the size of the left adrenal mass we elected to offer her a complete resection. The patient therefore underwent a laparoscopic adrenalectomy. Histopathological examination of the specimen revealed a high-grade, poorly differentiated NEC of the adrenal gland, small-cell type, with tumor necrosis. A baseline evaluation comprised an FDG-PET CT scan revealing the contralateral adrenal tumor, which was also partially resected to leave the patient with some functional adrenal tissue and not render her Addisonian. Although we found no pulmonary primary, a bleb was seen on chest CT that we hypothesized was possibly a burn-out primary in the setting of an immunogenic tumor.

CONCLUSION

Surgery played a vital role in our case followed by combination of chemoimmunotherapy as per present recommendation of a small-cell tumor especially since the patient presented with atypical clinical manifestations.

Primary small cell neuroendocrine cancer of adrenal gland: a rare extrapulmonary small cell cancer

Small cell cancer is an aggressive neoplasm of neuroendocrine origin that is most commonly found in the lungs. However, up to 5% of cases can be extrapulmonary. These have been reported to be located in the gastrointestinal and genitourinary systems and rarely in other locations. Only five prior cases of small cell cancer have been reported where the primary lesion is at the adrenal gland. Here we present the case of a female patient in her mid-50s who presented with right upper quadrant pain and was diagnosed with metastatic small cell carcinoma of the adrenal gland. The patient received palliative chemotherapy for her metastatic cancer and was ultimately admitted to hospice after progression of her disease. This case and the accompanying literature review highlight a rare manifestation of extrapulmonary small cell cancer.

Biochemically silent phaeochromocytoma presenting with non-specific loin pain

A 55-year-old woman presented with a 4-month history of right-sided non-specific loin pain and 6 kg weight loss. A CT scan of the abdomen and pelvis showed an incidental 4.5 cm right-sided adrenal lesion which was not typical of an adrenal adenoma. This was further confirmed on MRI of the adrenals. Biochemical investigations to investigate for a functional adrenal lesion included serum catecholamines and metanephrines, an aldosterone to renin ratio and an overnight dexamethasone suppression test. These were all negative. A laparoscopic adrenalectomy was performed in view of the large size of the lesion. Histology was consistent with a phaeochromocytoma, which confirmed the diagnosis of a non-secreting phaeochromocytoma. Non-secreting phaeochromocytomas are rare and usually found in patients with known genetic mutations. Adrenal lesions not related to any mutations similar to our case are even rarer and reported even less in the literature.

Primary small cell neuroendocrine carcinoma of adrenal gland

Neuroendocrine tumors are an extremely rare form of retroperitoneum tumor. A 79-year-old man presented with abdominal pain. Computed tomography and magnetic resonance imaging revealed a 51 × 36 mm mass in the left adrenal gland. Gastrofiberscopy, colonfiberscopy and positron emission tomography were performed and showed no lesions or other malignancies. Endocrine tests were normal. Two months later, the mass had grown to 68 × 52 mm. Suspecting a malignant tumor, we performed laparoscopic adrenalectomy. Histopathological diagnosis revealed the tumor was small cell neuroendocrine carcinoma. No other malignancies were revealed, so we diagnosed primary small cell neuroendocrine carcinoma of adrenal gland. To our knowledge, this is only the third report in English of primary small cell neuroendocrine carcinoma of the adrenal gland and the first report that is confined to the adrenal gland. Adrenal masses are often misdiagnosed as adenoma; however, we need to raise awareness of the potential for malignant adrenal tumors such as the rarer small cell neuroendocrine carcinoma.

Metabolic and anatomic characteristics of benign and malignant adrenal masses on positron emission tomography/computed tomography: a review of literature

PET/CT with (18)F-fluorodeoxyglucose (FDG) or using different radiocompounds has proven accuracy for detection of adrenal metastases in patients undergoing cancer staging. It can assist the diagnostic work-up in oncology patients by identifying distant metastases to the adrenal(s) and defining oligometastatic disease that may benefit from targeted intervention. In patients with incidentally discovered adrenal nodules, so-called adrenal "incidentaloma" FDG PET/CT is emerging as a useful test to distinguish benign from malignant etiology. Current published evidence suggests a role for FDG PET/CT in assessing the malignant potential of an adrenal lesion that has been 'indeterminately' categorized with unenhanced CT, adrenal protocol contrast-enhanced CT, or chemical-shift MRI. FDG PET/CT could be used to stratify patients with higher risk of malignancy for surgical intervention, while recommending surveillance for adrenal masses with low malignant potential. There are caveats for interpretation of the metabolic activity of an adrenal nodule on PET/CT that may lead to false-positive and false-negative interpretation. Adrenal lesions represent a wide spectrum of etiologies, and the typical appearances on PET/CT are still being described, therefore our goal was to summarize the current diagnostic strategies for evaluation of adrenal lesions and present metabolic and anatomic appearances of common and uncommon adrenal lesions. In spite of the emerging role of PET/CT to differentiate benign from malignant adrenal mass, especially in difficult cases, it should be emphasized that PET/CT is not needed for most patients and that many diagnostic problems can be resolved by CT and/or MR imaging.