November/December 2015
PERILS OF DERMATOPATHOLOGY
Figure 1. Case 1: section showing “murky” basaloid cells characteristic of Merkel cell carcinoma. Note also fibrous trabeculae within the lesion characteristic of this tumor and necrosis (hematoxylin and eosin stain, original magnification ×387).
Figure 3. Case 2: section showing atypical cells replacing the epidermis, well demarcated at the edges from normal epidermis and showing lack of normal epidermal maturation, all characteristic of eccrine porocarcinoma (hematoxylin and eosin stain, original magnification ×387).
Figure 2. Case 1: section showing a more bluish area of “murky” basaloid cells characteristic of Merkel cell carcinoma (hematoxylin and eosin stain, original magnification ×387).
Figure 4. Case 2: a Ki67 immunostain showing that most of the tumor cells are proliferating (original magnification ×387).
ular lobules of basaloid cells, and immunohistochemistry results were negative for cytokeratin 20. Positive staining for synaptophysin and clinical-pathological correlation assisted dermatopathologists in making the diagnosis of MCC.4 Confirmatory immunohistochemistry with cytokeratin 20 is recommended to avoid misdiagnosis,5 but, as this case demonstrated, this is not foolproof. MCC is also positive for chromogranin A, synpatophysin, and neuron-specific enolase, and special staining to de-
tect these compounds should be considered in ambiguous cases. Histologic features found in MCC but not basal cell carcinoma include relatively sparse cytoplasm, nuclear molding, necrosis, and absence of peripheral palisading and clefting, but these differences may be subtle or even absent.4,5
SKINmed. 2015;13:467–469
Eccrine porocarcinoma is a rare adnexal malignancy with an ambiguous presentation. As an aggressive cancer with fre-
468
Aggressive Skin Cancers Posing as Less Aggressive Cancers