Hematolymphoid and Dermatologic Pathology of the Head and Neck
Core Concepts
Recognize lymphoid proliferations and dermatologic lesions of the head and neck. Lymphoid: reactive hyperplasia, follicular hyperplasia, lymphoma (DLBCL, MALT, mantle cell, Hodgkin), and plasmacytic lesions. Dermatologic: basal cell carcinoma, squamous cell carcinoma, melanoma, seborrheic keratosis, and adnexal tumors. Understand the role of clonality studies (IGH rearrangement, kappa/lambda), flow cytometry, and IHC panels (CD3, CD20, CD5, CD10, BCL2, BCL6, cyclin D1, Ki-67).
Common Traps
- Calling MALT lymphoma a reactive process; look for lymphoepithelial lesions and clonality.
- Missing melanoma in an amelanotic lesion; use S100, SOX10, and Melan-A.
- Confusing basal cell carcinoma with trichoepithelioma; look for clefting and peripheral palisading.
- Overlooking Hodgkin lymphoma in a young adult with a neck mass and Reed-Sternberg cells.
Rule of Thumb
For a lymphoid infiltrate, ask whether the architecture is preserved and whether there is light-chain restriction. A worked example: a parotid mass with a dense lymphoid infiltrate and lymphoepithelial lesions - suspect MALT lymphoma and confirm clonality with IGH rearrangement and kappa/lambda restriction; reactive sialadenitis lacks monotypic restriction.
Dermatology Pearl
For pigmented lesions, apply the ABCDE criteria and correlate with dermoscopy; biopsy any changing lesion.