Faculty Bibliography

CONTEXT: - Pathologic diagnosis of tumors in the genitourinary system can be challenging based on morphology alone, particularly when diagnostic material is limited, such as in core biopsies. Immunohistochemical stain can be a useful tool to aid in the diagnosis. OBJECTIVE: - To provide an update on practical applications and interpretation of immunohistochemical stains in the diagnosis of tumors in prostate, kidney, bladder, and testis. We particularly focus on difficult differential diagnoses, providing our insights in frequently encountered challenging situations. Commonly used immunohistochemical panels are discussed. DATA SOURCES: - Review of literature and our own experience. CONCLUSION: - Immunohistochemical stain is a valuable tool in the diagnosis of genitourinary tumors when appropriately used.

BACKGROUND: Encapsulated non-invasive follicular variant papillary thyroid cancer (ENIFVPTC) has recently been re-termed noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). This designation specifically omits the word "cancer" to encourage conservative management since patients with NIFTP tumors have been shown to derive no benefit from completion thyroidectomy or adjuvant radioactive iodine (RAI) therapy. METHODS: IRB approved retrospective study of consecutive cases of tumors from 2007 to 2015 that met pathologic criteria for NIFTP. The Conservative Management (CM) group included patients managed with lobectomy alone or appropriately indicated total thyroidectomy. Those included in the Aggressive Management (AM) group received either completion thyroidectomy or radioactive iodine or both. RESULTS: From 100 consecutive cases of ENIFVPTC reviewed, 40 NIFTP were included for the final analysis. Of these, 10 (27%) patients treated with initial lobectomy received completion thyroidectomy and 6 of 37 (16%) also received post-surgical adjuvant RAI. The mean per-patient cost of care in the AM group was $17629+/-2865 nearly twice the $8637+/- 309 costs in the CM group, and was largely driven by the cost of completion thyroidectomy and RAI. CONCLUSIONS: The term NIFTP has been recently promulgated to identify a type of thyroid neoplasm, formerly identified as a low-grade cancer, for which initial surgery represents adequate treatment. We believe that since the new NIFTP nomenclature intentionally omits the word "cancer" the clinical indolence of these tumors will be better appreciated, and cost savings will result from a more conservative and appropriate clinical management.

Atypical intraductal cribriform proliferations of the prostate (AIP) are loose cribriform proliferations of luminal cells that exhibit greater architectural complexity and/or nuclear atypia than high-grade prostatic intraepithelial neoplasia (HGPIN), but lack the diagnostic criteria for intraductal carcinoma (IDC). The significance of AIP has not been formally established. We compared the clinical, morphologic, and immunohistochemical characteristics of AIP with classic IDC in 310 radical prostatectomy specimens that were received over an 18-month period. Of the 310 cases, 46 cases had AIP only (n=10), IDC only (n=6), or AIP coexisting with IDC (n=30). The ERG status of all 46 AIP/IDC cases was identical to the nearby acinar carcinoma, contrasted to just 3 cases of HGPIN (7%, P<0.01). The degree of uniform phosphatase and tensin homolog (PTEN) loss in 34 selected cases was identical in AIP and IDC (66.7%). No foci of HGPIN showed uniform PTEN loss; there was only 38% concordance of PTEN expression pattern between HGPIN and the nearby acinar carcinoma, unlike AIP and IDC (77% and 81%, respectively, P<0.01). AIP-associated and/or IDC-associated carcinoma (n=46) showed a higher stage and grade compared with acinar-only carcinoma (n=264, P<0.01). AIP-associated carcinoma had similar clinicopathologic features as IDC-associated carcinoma, including preoperative prostate-specific antigen, Gleason score, extraprostatic extension, seminal vesicle invasion, and lymph node metastasis (n=36, P>0.05). In conclusion, AIP shares similar ERG/PTEN immunoprofiles and exhibits similar clinical behavior as IDC, warranting immediate repeat biopsy when AIP is identified on biopsy, as is recommended in the most recent WHO Classification of Tumours of the Urinary System and Male Genital Organs, 2016.