PMC6046181_01
CT (a) and PET (b) images of the FDG-avid mass, centered along the anterior aspect of the right masseter muscle, not involving parotid.
CRIPA2018-9410465.001.jpg
PMC6046181_01_CRIPA2018-9410465.001.jpg
fig1
A PET-CT scan showed an FDG-avid 2.2 x 2.0 cm mass centered along the anterolateral aspect of the right masseter muscle without parotid gland involvement (Figure 1). Immunohistochemical stains showed S100 to be strongly and diffusely positive (Figure 2(e)); collagen IV was 2+ positive around individual tumor cells (Figure 2(f)); Mart1/MelanA and HMB-45 were negative (not shown).
(a), (b) Pap-stained cytologic preparations of the right parotid-region mass; (c), (d) hematoxylin and eosin-stained sections of the parotid-region mass; immunostains for S100 (e); collagen IV (f).
CRIPA2018-9410465.002.jpg
PMC6046181_01_CRIPA2018-9410465.002.jpg
fig2
A fine needle aspiration of the mass showed clusters of atypical spindled cells with elongated, irregular nuclei; the tumor was diagnosed as a malignancy consistent with neural or mesenchymal origin (Figures 2(a) and 2(b)). Histopathologic review showed a tumor adjacent to, but not primarily involving, the parotid gland, characterized by a proliferation of spindle cells, many with multiple nuclei, grouped in interwoven fascicles and heavily interwoven with lymphocytes (Figure 2(c)). Nuclei were prominent and markedly pleomorphic, and the mitotic index was high (28/10 high-power fields; Figure 2(d)). Immunohistochemical stains showed S100 to be strongly and diffusely positive (Figure 2(e)); collagen IV was 2+ positive around individual tumor cells (Figure 2(f)); Mart1/MelanA and HMB-45 were negative (not shown).
T1-weighted image with contrast, highlighting new right-sided cerebellopontine angle lesion (arrow).
CRIPA2018-9410465.003.jpg
PMC6046181_01_CRIPA2018-9410465.003.jpg
fig3
An MRI revealed a 6.4 mm, contrast-enhancing lesion at the right cerebellopontine (CP) angle (Figure 3) and a similar 3.8 mm lesion slightly distal running along the 7th cranial nerve.
Hematoxylin and eosin-stained section (a) and MART1/Melan A immunostain (b) demonstrating lentigo maligna melanoma of the right cheek (400X power).
CRIPA2018-9410465.004.jpg
PMC6046181_01_CRIPA2018-9410465.004.jpg
fig4
A punch biopsy of this lesion revealed LMM (Figure 4).
(a) Hematoxylin and eosin-stained section of CP angle tumor; immunostains for S100 (b), collagen IV (c), Mart1/Melan A (d), and HMB-45 (e).
CRIPA2018-9410465.005.jpg
PMC6046181_01_CRIPA2018-9410465.005.jpg
fig5
Histopathologic review demonstrated spindled-to-epithelioid cells with pleomorphic nuclei (Figure 5(a)). Similar to the original parotid-region mass, the tumor showed strong and diffuse positivity for S100 (Figure 5(b)), and there was weak focal reactivity for collagen IV (Figure 5(c)). Unlike the originally resected parotid-region mass, the CP angle lesion exhibited strong and diffuse positivity for Mart1/MelanA and HMB-45 (Figures 5(d) and 5(e)) and was diagnosed as malignant melanoma.