Solid papillary carcinomas (SPCs) are uncommon tumors composed of circumscribed large cellular nodules separated by bands of dense fibrosis. The aim of this study was to further elucidate the characteristics of SPC, the types and significance of invasive carcinomas associated with these tumors, and the long-term clinical outcome. Fifty-eight SPCs were analyzed (mean follow-up, 9.4 years). Cases were divided into three groups: 1) SPC only (32.7%), 2) SPC with extravasated mucin (8.6%), and 3) SPC with invasive components (58.7%) consisting of neuroendocrine-like (29.5%), colloid (23.5%), ductal not otherwise specified (14.5%), lobular (3%), tubular (3%), or mixed (26.5%). The mean age was 72 years. All were estrogen receptor positive and 86% were histologic grade 1. The total size of the tumor measured 0.3 to 15 cm. In the group with invasive carcinoma, the size of invasion was 0.1 to 4 cm. Axillary nodes were involved in 13% of the cases (6 of 46); all of these had an invasive component in the primary tumor. Local recurrence was seen in 5 patients, all from the group with invasive carcinoma. Overall, 11.7% died of their tumor, 1 to 4 years after diagnosis (mean, 2.3 years); none of them belongs to the group of noninvasive SPC. Five of the 6 patients who died of tumor had invasive components. The sixth patient who died with "metastatic signet-ring cell carcinoma" at 10 years was in the group of patients with SPC with extravasated mucin where the SPC lesion had prominent signet-ring cell features. In conclusion, SPCs are heterogeneous lesions that arise in older women and have an indolent behavior. Lymph node and distant metastases are uncommon and generally limited to cases with (conventional) invasive components.

For distinguishing PCAN from MC: (1) positivity for p63 and CK 5/6 are relatively specific and sensitive for PCAN, (2) CK 7 and 20 are neither sensitive nor specific, and (3) CK 7 positivity in PCAN was focal with a specific pattern in contrast to the diffuse positivity for MC.

Solitary fibrous tumor (SFT) is a relatively uncommon neoplasm that most commonly arises in the pleura. However, SFT is now known to affect various other anatomic sites as well, including rare examples in the skin, where the histologic features of this lesion may create diagnostic confusion with a variety of other spindle-cell tumors. In order to further the characterization of cutaneous SFT, all available cases of that entity were retrieved from the authors' institutional files. Immunohistochemical analysis for CD-34, CD-99, vimentin, bcl-2, factor XIIIa, S100 protein, smooth muscle actin, pankeratin, epithelial membrane antigen (EMA) and desmin was performed on those neoplasms and the corresponding clinical information was obtained whenever possible. There were eight men and two women in the study group, with a median age of 43 years. Sites of involvement included the trunk (two cases), cheek (two), scalp (one), forehead (one), lip (one), temple (one), heel (one) and toe (one). All patients were treated with local excision; only one lesion recurred locally, but it required multiple re-excisions. All of the neoplasms were composed of bland spindle cells with a variably fibrous but focally hyalinized collagenous stroma. A variety of case-specific growth patterns were observed. Mitoses were generally rare, ranging from 0 to 3 per 10 x400 microscopic fields. Immunostains showed reactivity for vimentin in all SFTs, CD-34 in 8 of 10 cases, CD-99 and bcl-2 in 4 of 10 (each) and smooth-muscle actin in 3 of 10 cases. None of the lesions was labeled for factor XIIIa, keratin, EMA, desmin or S100 protein. SFT of the skin appears to be a 'borderline' neoplasm that only uncommonly recurs. Immunoreactivity for CD-34, - especially together with bcl-2 or CD-99, or both - is helpful in identifying this tumor.

We conclude that an in situ component is frequently present in PCMC (5/7) and may help in distinguishing this entity from MMC, especially of breast origin. Furthermore, it may provide insight into the pathogenetic mechanism of mucinous carcinoma evolving from in situ carcinoma with luminal mucinous distention to cellular tumor with a little surrounding mucin.

p16INK4a is a sensitive and specific marker for distinguishing BD from AK/benign squamous cutaneous lesions and may be helpful as an adjunct to histomorphology in the diagnosis and appropriate clinical management of these lesions.