Setting: Comprehensive cancer center.Patients: Fifty-one patients (21 men and 30 women) with biopsy-proven skin metastases and correlative clinical data.Interventions: Four dermatopathologists reviewed a random mixture of metastases and primary skin tumors. Immunohistochemical studies for 12 markers were performed on the metastases, with skin adnexal tumors as controls.Main Outcome Measures: Clinical characteristics of cutaneous lesions, clinical outcomes, histologic features, and immunohistochemical markers.Results: Eighty-six percent (43 of 50) of the patients had known stage IV cancer, and skin metastasis was the pre-

Immunohistochemistry (IHC) is an important adjunctive test in diagnostic surgical pathology. We studied the clinical significance and outcomes in performing IHC on cases with a previous diagnosis of cancer who are coming to the Fox Chase Cancer Center (FCCC), a National Cancer Institute designated National Comprehensive Cancer Center (NCCC), for treatment and/or second opinion. We reviewed all the outside surgical pathology slide review cases seen at the FCCC for 1998 and 1999 in which IHC was performed. Cases were divided into the following: confirmation of outside diagnoses without and with prior IHC performed by the outside institution (groups A and B, respectively) and cases with a significant change in diagnosis without and with prior IHC performed by the outside institution (groups C and D, respectively). During 1998 and 1999, 6678 slide review cases were reviewed at the FCCC with an overall significant change in diagnosis in 213 cases (3.2%). IHC was performed on 186 of 6678 (2.7%) slide review cases with confirmation of the outside diagnosis in 152 (81.7%) cases and a significant change in diagnosis in 34 (18.3%) cases. Patient follow-up was obtained in 32 of 34 (94.1%) cases with a significant change in diagnosis (groups C and D), which confirmed the correctness of our diagnosis in 26 of 27 cases (96%; in five cases follow-up was inconclusive). We repeated the identical antibodies performed by the outside institutions in group D (37 antibodies) and group B (133 antibodies) with different results in 48.6% and 13.5%, respectively (overall nonconcordance 21.2%). In group D additional antibody tests beyond that performed by the outside institution were needed in 88.8% of cases to make a change of diagnosis. In the setting of a NCCC, reperforming and/or performing IHC on cases with a previous diagnosis of cancer is not a duplication of effort or misuse of resources. Repeating and/or performing IHC in this setting is important in the care and management of patients with cancer.

Forty‐four cases of biopsy‐proven cutaneous metastases from internal organ or soft tissue malignancies were retrieved at a single institution from 1990 to 2004. All cases had detailed clinical and follow‐up data. There were 19 males and 25 females, with a wide age range (37–86 years). Most (75%) had advanced (stage IV) disease at the time of metastasis. In four patients skin metastasis was the presenting lesion. The most common primary site for men is lung and for women, breast and lung. In nearly half of patients cutaneous metastasis was not the clinical diagnosis. The prognosis was grave (67% died of disease within a median of 7 months). Independent, blinded review by four dermatopathologists showed that without a detailed clinical history, most metastases from carcinomas were correctly suspected based on histologic patterns. However, metastases from small cell carcinomas and sarcomas were difficult to distinguish from primary skin tumors. Histologic recognition of a primary site was often difficult without pertinent clinical history. None of the metastasis had a combined immunohistochemical profile of B72.3 (−), CA125 (−), calretinin (+), p63 (+) and CK5/6 (+), which was commonly seen in skin adnexal tumors. This immunohistochemical panel appears to best differentiate the two entities.