An unusual case of melanoma metastasis in the buccal space: learning by mistakes to distinguish it from salivary neoplasms

Abstract

Background: The buccal space is an unusual location of malignancies. We report here the case of a woman with a melanoma metastasis in buccal fat pad, to evaluate the imaging features which might lead to the correct, although uncommon, diagnosis.

Case presentation: A 71-year-old woman presented with a painless visible swelling of the left cheek. MRI revealed the presence of a solid lesion located in the buccal fat pad with features suggestive of malignancy. It showed T1 hyperintensity and T2 hypointensity, and restriction of diffusion. Histological examination showed neoplastic cells compatible with melanoma.

Discussion: The lesion features (T1 hyperintensity and T2 hypointensity) initially lead our team to believe that there was a hemorrhagic component, possibly a residue of the biopsy. However, when associated with other malignancy features, such as low apparent diffusion coefficient (ADC) values and contrast enhancement, they should evoke the suspect of melanoma, provided that no biopsy was performed and no trauma occurred in the 3-7 days before.

Keywords: Buccal fat pad; MRI features; Melanoma; Melanoma metastasis.

Fig. 1

Anatomy of the buccal space

Fig. 2

Magnetic resonance imaging revealed a solid mass located in the left buccal space. a The lesion (arrow) showed a focal component with high signal intensity on axial T1-weighted imaging and b low signal intensity on T2-weighted imaging and c on fat-saturated T2 STIR sequences. d Diffusion-weighted imaging revealed a restricted diffusion change with e low apparent diffusion coefficient of 0.9. f After intravenous contrast administration, the lesion showed increased signal intensity on T1-weighted imaging

Fig. 3

Microscopic pictures of the surgical specimen. a–d H&E stain at increasing magnification (respectively, × 40, × 100, × 200, and × 400) showing proliferating atypical cells containing coarse-brownish granules suspected to be melanin; e, f, respectively, S-100 and SOX10 immunohistochemical stains confirming the diagnosis of melanoma

Fig. 4

[F-18]FDG PET-CT reveals avid FDG uptake by the left buccal space lesion (a). Multiple pathological radiotracer hyper-accumulation localizations were present, such as in a voluminous left axillary lymph node (b), a perigastric solid lesion (c), and in the muscular tissue of the left thigh (d)