Trichoepithelioma and Spiradenoma Collision Tumor

Cylindromas are composed of basaloid islands interconnected in a jigsaw puzzle configuration (Figure 5B).⁴ Similar to spiradenomas, they also are composed of 2 cell populations. Characteristically, the tumor islands are outlined by a hyalinized eosinophilic basement membrane. Hyalinized droplets of basement membrane zone material also may be noted in the islands. Unlike spiradenomas, they lack both intratumoral lymphocytes and a trabecular growth pattern. Although spiradenocylindromas (cylindroma and spiradenoma collision tumors) are perhaps the most common collision tumor associated with Brooke-Spiegler syndrome, there is no evidence suggesting the presence of a cylindroma in the current case.

Figure 5. Adenoid cystic carcinoma is composed of variably sized cribriform islands of basaloid to pink cells concentrically arranged around glandlike spaces filled with mucin (A)(H&E, original magnification ×20). Cylindromas are composed of basaloid islands interconnected in a jigsaw puzzle configuration. Characteristically, the tumor islands are outlined by a hyalinized eosinophilic basement membrane (B) (H&E, original magnification ×100).

Primary cutaneous mucinous carcinoma is a rare neoplasm with a predilection for the eyelids; lesions occurring outside of this facial distribution, particularly of the breast, warrant a workup for metastatic disease.⁷ It typically occurs in the deeper dermis with involvement of the subcutaneous fat and is characterized by delicate fibrous septa enveloping large lakes of mucin, which contain islands of tumor cells (Figure 6). It has not been reported in association with spiradenomas. In addition, the tumor cells typically are CK7 positive.

^{Figure 6. Mucinous carcinoma is characterized by delicate fibrous septa enclosing large lakes of mucin containing islands of tumor cells (H&E, original magnification ×20).}