Anatomic Abstracts

August 2005

Editors:
Michael Cibull, MD
Subodh Lele, MD
Melissa Kesler, MD

Use of AMACR (P504S) and basal cell markers in assessing routine prostate needle biopsy specimens
Immunohistochemical panel of antibodies in the diagnosis of brain metastases of the unknown primary
Oral squamous cell carcinoma: histologic risk assessment and local disease-free and overall survival

Use of AMACR (P504S) and basal cell markers in assessing routine prostate needle biopsy specimens

Distinguishing benign prostate glands from malignant ones based on morphology on prostatic core needle biopsy specimens can be difficult, particularly if the suspicious focus is small. Several immunohistochemical markers, including the basal cell cocktail, 34bE12 and p63, and the prostate cancer biomarker alpha-methylacyl-CoA-racemase (AMACR) have in recent years been used as adjuvants to morphology in diagnostically challenging cases. The authors of this study prospectively addressed the diagnostic utility of the basal cell cocktail in combination with the commercially available AMACR monoclonal antibody, P504S, on prostatic core needle biopsy specimens (PNBs) that require immunohistochemistry studies to make a diagnosis. The authors assessed the day-to-day practice in an academic setting to determine how often these immunohistochemistry tests were used on routine PNBs and to establish how often a combination of the basal cell cocktail and P504S was helpful in diagnosing prostate cancer. A total of 772 prospectively collected PNB cases were examined over a seven-month period. Immunohistochemistry staining was performed in 171 cases (22 percent); 123 cases were stained with the basal cell cocktail in addition to the commercially available monoclonal AMACR antibody. In 86 of these 123 cases (70 percent), both stains contributed to the final diagnosis: PCa in 44 cases, benign in 33 cases, and high-grade prostatic intraepithelial neoplasia in nine cases. Of the remaining 37 cases (30 percent), 18 were called benign or PCa based solely on appropriate staining with the basal cell cocktail, with AMACR being noncontributory because the focus of interest had been cut through (12 cases); there was negative staining with AMACR (in four PCa cases) or there was positive staining with AMACR (in two benign cases showing atrophy). Nineteen of 37 cases were diagnosed as atypical small acinar proliferation. In these 19 cases, either the focus had been cut through on one or both of the stains (11 cases), both AMACR and basal cell cocktail failed to work (two cases), AMACR was positive in the presence of patchy basal cell cocktail staining (one case), AMACR was negative in the absence of basal cell cocktail staining (three cases), or despite appropriate staining, the focus consisted of one gland and was considered too small to call carcinoma (two cases). Additional immunohistochemistry stains were performed in 171 of 772 cases; of these, 123 had sufficient material to perform both the basal cell cocktail and P504S. The basal cell cocktail, when used in combination with AMACR, rendered a diagnosis in almost 70 percent of cases. Using these stains in combination may be a better approach in diagnostically difficult cases as it increases the likelihood that a definitive diagnosis can be rendered while decreasing the likelihood of an equivocal diagnosis. However, a limitation of this approach is the loss of tissue in the small lesions, which suggests that combining AMACR and basal cell cocktail on a single slide would be superior to using either marker separately.

Browne TJ, Hirsch MS, Brodsky G, et al. Prospective evaluation of AMACR (P504S) and basal cell markers in the assessment of routine prostate needle biopsy specimens. Hum Pathol. 2004;35:1462-1468.

Reprints: Dr. Mark A. Rubin, Dept. of Pathology (Amory 3-195), Brigham and Women's Hospital/Harvard Medical School, 75 Francis St., Boston, MA 02115

Immunohistochemical panel of antibodies in the diagnosis of brain metastases of the unknown primary

The primary tumor of brain metastases is unknown in up to half of such metastases at the time of neurosurgery. The authors investigated 54 consecutive unselected brain metastases immunohistochemically using antibodies against different intermediate filaments and tumor markers. By correlating the immunohistochemical results with the location of the primary tumor, the authors could establish a staining pattern characteristic of the most frequent metastases. Subsequently, 40 cases with known primary tumor were blinded and re-evaluated based on their immunohistochemical staining pattern. The most common primaries were lung (20.4 percent), colorectum (11.1 percent), melanoma (7.4 percent), and breast (7.4 percent). The primary was unknown in 14 (25.9 percent) cases. The characteristic immunohistochemical profiles of brain metastases were found to be positivity of cytokeratin 7 and thyroid transcription factor-1 (TTF-1) pointing to the lung, positivity of cytokeratin 20 and negativity of cytokeratin 7 pointing to the colorectum, positivity of vimentin and protein S100 and negativity of cytokeratins pointing to a melanoma, and positivity of cytokeratin 7 and CA 15-3 with negativity of TTF-1, CA 125, and CA 19-9 pointing to the breast. These primaries comprised the majority in the authors' series. Using the established panel of immunohistochemical markers, the authors were able to identify the primary in 29 out of 40 (72.5 percent) brain metastases. The authors concluded that a combination of antibodies against different cytokeratins, vimentin, protein S100, TTF-1, and CA 15-3 can point to the primary site in brain metastases of the unknown primary.

Drlicek M, Bodenteich A, Urbanits S, et al. Immunohistochemical panel of antibodies in the diagnosis of brain metastases of the unknown primary. Pathol Res Pract. 2004;200:727-734.

Reprints: Marcus Drlicek at marcus.drlicek@kin.at

Oral squamous cell carcinoma: histologic risk assessment and local disease-free and overall survival

The authors conducted a study that was retrospective and prospective in design to analyze the impact of resection margin status and histologic prognosticators on local recurrence and overall survival for patients with oral squamous cell carcinoma. Study cohort one referred to the entire group of 292 patients with oral squamous cell carcinoma (OSCC). The slides from the earliest resection specimens from cohort one were examined in an exploratory manner for multiple parameters. Cohort two referred to a subset of 203 patients who did not receive any neoadjuvant therapy and had outcome data. Cohort three represented a subset of cohort two (n=168) wherein the histologic resection margin status could be reconfirmed. Cohort four referred to a subset of 85 patients with tongue/floor of mouth tumors. Margin status was designated as follows: group one, clearance of 5 mm or more with intraoperative analysis, no need for supplemental margins (n=46); group two, initial margins were measured as less than 5 mm during intraoperative frozen section, supplemental resection margins were negative on final pathology (n=73); group three, final pathology revealed resection margins of less than 5 mm (n=30); group four, final pathology revealed frankly positive resection margins (n=19). The endpoints of local recurrence and overall survival were queried with respect to T stage, tumor site, margin status, and numerous histologic variables by Cox regression and Kaplan-Meier survival analyses. Tumor stage (T) was significantly associated with local recurrence (P=0.028). Kaplan-Meier analysis for stage and intraoral site was significantly associated with local recurrence for T4 tumors. The increased likelihood of local recurrence was higher for T4 OSCC of the buccal mucosa (75 percent), sinopalate (50 percent), and gingiva (100 percent) compared with mobile tongue (27 percent) and oropharynx (13 percent) (P=0.013). Margin status was not associated with local recurrence or overall survival (cohort three). This was so when all tumors were grouped together and when separate analyses were performed by tumor stage and oral subsite. No significance was demonstrated when margin status was examined for patients with similar treatment (surgery alone or surgery with adjuvant RT). However, the administration of adjuvant RT significantly increased local disease-free survival (P=0.0027 and P=0.001 for T1 and T2 OSCC, respectively). On exploratory analyses of histologic parameters, worst pattern of invasion was significantly associated with local recurrence (P=0.015) and overall survival (P<0.001). Perineural invasion involving large nerves (greater than 1 mm) was also associated with local recurrence (P= 0.005) and overall survival (P=0.039). Limited lymphocytic response too was significantly associated with local recurrence (P=0.005) and overall survival (P=0.001). When used as covariates in a multivariate Cox regression model, worst pattern of invasion, perineural invasion, and lymphocytic response were significant and independent predictors of local recurrence and overall survival, even when adjusting for margin status. Thus, these factors were used to generate risk assessment. The authors’ risk assessment classified patients into low-, intermediate-, or high-risk groups with respect to local recurrence (P=0.0004) and overall survival (P<0.0001). This classification retained significance when examining patients with uniform treatment. In separate analyses for each risk group, the authors found that administration of adjuvant radiation therapy is associated with increased local disease-free survival for high-risk patients (P=0.0296) but not low-risk or intermediate-risk patients. Resection margin status alone is not an independent predictor of local recurrence and cannot be the sole variable in the decisionmaking process regarding adjuvant radiation therapy. The authors suggested that the recommendation of adjuvant radiation therapy be based on not only traditional factors, such as inadequate margin, perineural invasion, and bone invasion, but also histologic risk assessment. If clinicians want to avoid the debilitation of adjuvant radiation therapy, a 5-mm margin standard may not be effective with a high-risk score.

Brandwein-Gensler M, Teixeira MS, Lewis CM, et al. Oral squamous cell carcinoma: histologic risk assessment, but not margin status, is strongly predictive of local disease-free and overall survival. Am J Surg Pathol. 2005;29:167-178.

Reprints: Dr. Margaret Brandwein-Gensler, Albert Einstein College of Medicine, Montefiore Medical Center, Moses Division, Dept. of Pathology, ENT, 111 E. 210th St., Bronx, NY 10467; mgensler@montefiore.org

Dr. Cibull is professor of pathology and laboratory medicine and direct of surgical pathology, University of Kentucky Medical Center, Lexington. Dr. Lele is assistant professor of pathology and laboratory medicine, University of Kentucky Medical Center. Dr. Kesler is hematopathology fellow, University of Texas Southwestern Medical Center at Dallas.