Built for the resident staring down an unknown slide at sign-out, this handbook connects gross specimen handling and histologic pattern recognition to the immunohistochemical, molecular, and morphologic discriminators that resolve a diagnosis under time pressure. It moves organ system by organ system - head and neck, thoracic, gastrointestinal, genitourinary, gynecologic, breast, soft tissue, dermatopathologic, hematopathologic, and neuropathologic - from gross triage through the ancillary workup that separates a benign mimic from a malignant look-alike. The Morphologic Decision Map threads every chapter, naming the exact branch point where diagnoses diverge and the finding that locks the correct call.

Each Decision Map delivers the pattern, the fork, the discriminator panel, and the trap that catches the unwary, consolidated into an indexed Atlas for lookup during live sign-out.

What This Handbook Puts at Your Microscope

- Grossing and sampling protocols that determine diagnostic yield - the specimen-handling decisions that make or break every downstream call.
- Nuclear feature analysis for papillary thyroid carcinoma - grooves, pseudoinclusions, and chromatin clearing that separate it from hyperplastic mimics.
- MDM2 FISH interpretation for well-differentiated liposarcoma - resolving the fork that morphology alone cannot settle.
- Secretory carcinoma recognition in triple-negative breast lesions - the ETV6-NTRK3 workup that changes the diagnosis.
- Transplant biopsy interpretation using Banff scoring - distinguishing rejection from recurrent disease, plus PTLD classification and TA-TMA recognition.
- Intraoperative frozen section decision-making - organ-specific pitfalls and the discordance traps that cost margins.
- Molecular-first tumor classification per WHO fifth edition - NGS-defined entities like CIC-rearranged sarcoma and the panel that identifies them.
- AP board-relevant staging and diagnostic criteria, weighted for candidates preparing for certification.