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Collision Adrenal Tumors on PET/CT

¹ Massachusetts General Hospital Boston, MA 02114
² St. Elizabeth's Medical Center Boston, MA 02135
³ Massachusetts General Hospital Boston, MA 02114

A 46-year-old man presented to a surgical clinic with a palpable right groin mass that was subsequently resected through an inguinal approach. Findings of pathology revealed a high-grade leiomyosarcoma of the right spermatic cord. A PET/CT scan (Reveal XVI, CPS Innovations) with FDG was obtained to assess metastatic disease. The unenhanced CT component showed a well-circumscribed 2.5-cm mass in the superior portion of the left adrenal gland measuring 4 H, thereby meeting established CT criteria for adenoma [1] (Fig. 2A). The inferior left limb was also slightly thickened and of higher attenuation (Fig. 2B). The PET component showed intensely increased uptake of FDG that was initially thought to originate in the adrenal adenoma. However, after careful coregistration of the PET/CT images, it became clear that the intense uptake originated from the thickened inferior limb rather than from the superior mass (Figs. 2C and 2D). This finding prompted a targeted CT-guided adrenal biopsy of both the thickened inferior limb and the well-defined superior mass. Fine-needle aspirations and core biopsy samples of both the superior mass, thought to represent an adenoma, and the subtly thick-ened inferior adrenal limb were then obtained. Pathologic analysis of the superior mass showed benign cortical cells consistent with an adenoma and confirmed the characterization on imaging. Analysis of the thickened inferior limb revealed scattered groups of epithelial and spindle cells that were suggestive of sarcoma. This finding was consistent with stage IV disease, and the patient is currently undergoing chemotherapy.

View larger version (117K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A. —46-year-old man with spermatic cord leiomyosarcoma. CT images of left adrenal gland show superior rounded mass (arrow, A) measuring 4 H, consistent with adenoma and mild thickening of lateral limb (arrow, B) of higher attenuation.

View larger version (138K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B. —46-year-old man with spermatic cord leiomyosarcoma. CT images of left adrenal gland show superior rounded mass (arrow, A) measuring 4 H, consistent with adenoma and mild thickening of lateral limb (arrow, B) of higher attenuation.

View larger version (76K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2C. —46-year-old man with spermatic cord leiomyosarcoma. Fused PET/CT images show no significant uptake from superior mass (C) and intense FDG uptake from thickened lateral limb (arrow, D).

View larger version (75K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2D. —46-year-old man with spermatic cord leiomyosarcoma. Fused PET/CT images show no significant uptake from superior mass (C) and intense FDG uptake from thickened lateral limb (arrow, D).

Unenhanced CT and FDG PET have both proven useful for characterizing benign and malignant adrenal masses [1, 2]. A meta-analysis of the adrenal CT literature revealed that a threshold of 10 H distinguishes lipid-rich adenomas originating from nonadenomas from malignancies with a high specificity. FDG PET has also been found to be accurate in making this distinction; adenomas typically show little or no FDG uptake, but metastases usually show uptake greater than that of the liver. However, rare anecdotal cases of FDG-avid adrenal cortical adenomas [3] and the coexistence of adrenal cortical tumors and metastases have been reported on MRI [4]. To our knowledge, this is the first reported case of a collision adrenal tumor shown on hybrid PET/CT. Careful coregistration of PET and CT data, feasible with hybrid PET/CT studies, was vital in establishing the thickened inferior limb of the left adrenal gland versus the more conspicuous adrenal adenoma on CT as the source of the increased FDG uptake. This case alerts us to the possible coexistence of adrenal tumors and to the fact that subtly thickened adrenal glands can harbor metastases, both of which emphasize the need for meticulous technique both in the performance and the interpretation of PET/CT studies.

References

1. Boland GWL, Lee MJ, Gazelle SG, Halpern EF, McNicholas MM, Mueller PR. Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature. AJR1998; 171:201 -204[Abstract/Free Full Text]
2. Maurea S, Mainolfi C, Bazzicalupo L, et al. Imaging of adrenal tumors using FDG PET: comparison of benign and malignant lesions. AJR 1999;173:25 -29[Abstract/Free Full Text]
3. Shimizu A, Oriuchi N, Tsushima Y, Higuchi T, Aoki J, Endo K. High [18F] 2-fluoro-2-deoxy-D-glucose (FDG) uptake of adrenocortical adenoma showing subclinical Cushing's syndrome. Ann Nucl Med 2003;17:403 -406[Medline]
4. Schwartz LH, Macari M, Huvos AG, Panicek DM. Collision tumors of the adrenal gland: demonstration and characterization at MR imaging. Radiology1996; 201:757 -760[Abstract/Free Full Text]

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