PMC3673403_01
Computed tomography (CT) scan with contrast showing an 8.5 x 10.5 cm, heterogeneous, lobulated, and large mass in the left groin, compressing the left common femoral vein and inseparable from the vein as well as from the adductor muscles ventrally. The mass is associated with local lymphadenopathy, multiple small subcutaneous nodules, and an enlarged left external iliac lymph node.
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fig1
The mass was associated with local lymphadenopathy, multiple small subcutaneous nodules, and an enlarged left external iliac lymph node measuring around 1 x 1.5 cm (Figure 1).
Positron emission tomography (PET) scan showing left inguinal hypermetabolic, heterogeneous, and lobulated mass lesion with few nodal lesions in the same vicinity consistent with the known Merkel cell carcinoma.
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In the vicinity, there were few nodal lesions with moderate activity, mostly related to local metastatic disease (Figure 2).
Merkel cell carcinoma. (a) Macroscopic examination of the resected mass showing a large, yellow-tanned, and lobulated mass. (b) H&E stain showing sheets of small blue cells with scant cytoplasm, irregular nuclei, mitoses, and individually necrotic cells. (c) H&E stain showing invasion of femoral lymph node by nests of neoplastic cells. (d) The neoplastic cells stain positive for CK20 in a perinuclear dot-like fashion. (e) The neoplastic cells stain positive for CD 56.
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Macroscopic examination revealed a large, solid, firm, yellow-tanned, and lobulated mass measuring 11 x 10.5 x 9.5 cm (Figure 3(a)). Microscopic examination showed a tumor composed of small uniformly sized blue neoplastic cells with round to oval nuclei, scant cytoplasm, distinct nuclear membranes, finely dispersed nuclear chromatin, and inconspicuous nucleoli (Figure 3(b)). In addition, nests of neoplastic cells metastasizing to the left femoral lymph node were noted (Figure 3(c)). The neoplastic cells expressed cytokeratin 20 (CK20) in a perinuclear dot-like fashion (Figure 3(d)). Further, the neoplastic cells also expressed CD56 showing cytoplasmic and membranous positivity (Figure 3(e)).