Abstract
Malignant eccrine spiradenoma (MES) is an exceedingly rare neoplasm of cutaneous
adnexal origin. To date, 31 cases have been documented in the literature. We
herein report an additional case of MES that arose in longstanding eccrine
spiradenoma (ES). A 54-year-old woman was seen for a bluish nodular mass on the
right flank that previously had been stable for 7 to 8 years and had recently
increased in size and become tender. The excised mass (2.8 x 2.5 x 2.5 cm) had
no attachment to the overlying epidermis. Microscopically, 2 to 3 sharply
demarcated lobules were surrounded by a markedly thickened and hyalinized
fibrous capsule. Of the lesion removed, approximately 20% of the tumor showed
typical histologic features of benign ES. In the remaining malignant areas, the
typical configuration of benign counterpart, consisting of peripheral rows of
small dark basaloid cells and central layers of large pale cells partially
forming lumina, was replaced with a massive solid proliferation of large pale
cells showing nuclear pleomorphism, prominent nucleoli, increased mitotic
activity (reaching 12/10 HPF) and loss of PAS-positive basement membrane. There
were multiple foci of florid squamous differentiation in the malignant portion.
Cytokeratin, focally S-100 and EMA were expressed in large pale cells, whereas
alpha smooth muscle actin and S-100 were positive in small dark basaloid cells.
Focal reactivity of CEA and EMA was found in the central lumina. P53 was not
expressed in benign areas, whilst in malignant areas an occasional nuclear
reaction was disclosed.