Apocrine intraductal carcinomain situin nevus sebaceus: two case reports

Phacomatosis spilosebacea: A new name for a distinctive binary genodermatosis

Phacomatosis pigmentokeratotica (PPK) is defined by the association of papular nevus spilus arranged in a flag-like pattern and sebaceous nevus following Blaschko's lines. A systematic search of the worldwide literature retrieved 95 well-established PPK cases. An additional 30 cases were excluded for a number of reasons. Based on this study, we propose to rename PPK phacomatosis spilosebacea (PSS). Mosaic mutations of the HRAS gene are the only proven cause of PSS. The extracutaneous abnormalities of PSS result from various degrees of intermingling of Schimmelpenning syndrome and papular nevus spilus syndrome. PSS seems to be a condition at particularly high risk of developing basal cell carcinoma, urogenital malignancies, and vitamin D-resistant hypophosphatemic rickets. Extracutaneous abnormalities were detected in approximately 75% of PSS cases.

Nevus Sebaceous of the Scalp With Stepwise Progression Into Invasive Syringocystadenocarcinoma Papilliferum

Syringocystadenocarcinoma papilliferum (SCACP), the malignant counterpart of syringocystadenoma papilliferum (SCAP), is an extremely rare malignant adnexal neoplasm. It is described by the World Health Organization as a malignant transformation of SCAP occurring in middle-aged to elderly individuals with a predilection for the head and neck. SCACP seems to arise from a long-standing syringocystadenoma probably on a background of nevus sebaceous (NS) through a multistep progression. A 75-year-old man was referred to our department with a long-standing NS with a recent newly developing nodule on his scalp. The tumor was excised. On histology, the overall architecture of the tumor still resembled an unusual SCAP within NS but simultaneously showed transition to syringocystadenocarcinoma papilliferum in situ and invasive SCACP as recognizable by the presence of areas of nuclear atypia, increased proliferative activity, and infiltrative growth. In summary, we report an extremely rare case of an invasive SCACP of the scalp that demonstrates histological evidence for all transitive steps in the hypothetical multistep progression from NS to invasive SCACP in one single lesion. The implications of these findings are discussed in the light of the relevant literature.

Malignant Sweat Gland Tumors

Malignant sweat gland neoplasms are a confusing area within dermatopathology, with many entities reported under several designations in the literature. This review describes the key clinical and histopathologic features of select malignant adnexal neoplasms, including porocarcinoma, papillary carcinoma, adenoid cystic carcinoma, cribriform carcinoma, apocrine hidradenocarcinoma, malignant mixed tumor of the skin, syringoid carcinoma, cylindrocarcinoma, spiradenocarcinoma, mucinous carcinoma, polymorphous sweat gland carcinoma, microcystic adnexal carcinoma, secretory carcinoma of the skin, and primary cutaneous signet ring cell carcinoma. For entities with overlapping features, differential diagnoses are discussed.