To the Editor: There is a higher incidence of nonmelanoma skin cancer in patients with chronic lymphocytic leukemia and it seems to exhibit a heightened aggressive nature and higher rates of recurrence after Mohs surgery.1Mehrany K. Weenig R.H. Pittelkow M.R. Roenigk R.K. Otley C.C. High recurrence rates of basal cell carcinoma after Mohs surgery in patients with chronic lymphocytic leukemia.Arch Dermatol. 2004; 140: 985-988Crossref PubMed Scopus (61) Google Scholar,2Mehrany K. Weenig R.H. Pittelkow M.R. Roenigk R.K. Otley C.C. High recurrence rates of squamous cell carcinoma after Mohs' surgery in patients with chronic lymphocytic leukemia.Dermatol Surg. 2005; 31: 38-42Crossref PubMed Scopus (79) Google Scholar There are many postulated reasons with no well-defined pathogenesis.3Ravandi F. O'Brien S. Immune defects in patients with chronic lymphocytic leukemia.Cancer Immunol Immunother. 2006; 55: 197-209Crossref PubMed Scopus (117) Google Scholar Interpretation of histological section can often be complicated by the presence of dense, monomorphic lymphocytic infiltrates as it may not be clear whether the infiltrate is part of the leukemic process or part of a reaction to residual carcinoma.4Wilson M.L. Elston D.M. Tyler W.B. Marks V.J. Ferringer T. Dense lymphocytic infiltrates associated with non-melanoma skin cancer in patients with chronic lymphocytic leukemia.Dermatol Online J. 2010; 16: 4Crossref PubMed Google Scholar We performed an institutional review board–approved retrospective review of all patients with chronic lymphocytic leukemia treated with Mohs surgery at the University of Wisconsin Madison within the past 20 years and propose to review the following: (1) demographics, (2) tumor characteristics and outcomes, (3) frequency and patterns of peritumoral infiltrate (defined as dense collections of mononuclear cell aggregates of approximately 50 cells or more) on Mohs slides, and (4) correlation with disease severity at the time of Mohs surgery. For each patient selected, we reviewed all Mohs slides of tumors treated within the past 10 years. Twenty patients (6 females, 14 males) and 119 tumors were included. Mohs slides were reviewed for the 82 tumors treated in the past 10 years. The tumors included 64 squamous cell carcinomas (SCCs), 38 basal cell carcinomas, 16 squamous cell carcinomas in situ, and 1 “carcinoma.” Brigham Women Hospital staging (for SCCs) included 35 T1 tumors (54.7%), 19 T2a tumors (29.7%), 8 T2b tumors (12.5%), and 2 T3 tumors (3.1%). Five cases had perineural invasion. Peritumoral infiltrate was present on 12/82 (14.6%) tumors in 6 patients. Peritumoral infiltrate was present on every tumor in these 6 patients. The remaining 14 patients had no peritumoral infiltrate present on any of their tumors. Peritumoral infiltrate was present diffusely with focal evidence of residual tumor in 9/12 (75%) of tumors (Fig 1) versus diffusely without clear evidence of residual tumor in 3/12 (25%) of tumors. An additional layer was not taken in the 3 cases without clear evidence of residual tumor. There was no clear correlation with tumor type, stage of SCC, lymph node involvement, systemic treatment, lymphocyte count, or Rai score, which is a prognostic indicator used in chronic lymphocytic leukemia (Table I).5Rai K. Stilgenbauer S. Staging and Prognosis of Chronic Lymphocytic Leukemia. UpToDate, 2022Google Scholar The average number of layers taken on tumors with peritumoral infiltrate present was 2.7 in comparison to 1.9 when no peritumoral infiltrate was present. There were 7 recurrent tumors (5.9%) with no clear correlation to the presence of peritumoral infiltrate. There were no patients with known nodal or metastatic disease.Table ICharacteristics of tumors with peritumoral infiltratePatientAgeTumor typeLocationSCC BWH staging# of Mohs layersPeritumoral infiltrate patternRai score∗Rai score is a prognostic indicator used in patients with chronic lymphocytic leukemia with lymphocytosis. It is calculated based on 5 categories including enlarged lymph nodes, enlarged spleen, enlarged liver, anemia (Hgb <11 g/dL), and thrombocytopenia (platelets <100,000/mm3)Lymphocyte countNode involvementSystemic treatment174BCCL preauricular cheekx1Diffuse with tumor present120YesNone174BCCL nasal sidewallx3Diffuse with tumor present120YesNone279SCCVertex scalpT33Diffuse with tumor present01230NoNone280BCCR nasal sidewallx2Diffuse with tumor present01230NoNone383SCCL cheekT12Diffuse with tumor present117,914YesNone384BCCL upper lipx3Diffuse with tumor present479,442YesNone386SCCR templeT2a1Diffuse without tumor present3248,560NoNone387SCCVertex scalpT2a2Diffuse with tumor present317,990NoIbrutinib485SCCL lateral foreheadT311Diffuse with tumor present117,384NoNone576BCCL nasal alax1Diffuse without tumor presentxUnknownUnknownUnknown679SCCMidline chestT11Diffuse without tumor present416,800NoNone679SCCR upper armT2a2Diffuse with tumor present416,800NoNoneBCC, Basal cell carcinoma; BWH, Brigham Women Hospital; SCC, squamous cell carcinoma.∗ Rai score is a prognostic indicator used in patients with chronic lymphocytic leukemia with lymphocytosis. It is calculated based on 5 categories including enlarged lymph nodes, enlarged spleen, enlarged liver, anemia (Hgb <11 g/dL), and thrombocytopenia (platelets <100,000/mm3) Open table in a new tab BCC, Basal cell carcinoma; BWH, Brigham Women Hospital; SCC, squamous cell carcinoma. There was a higher SCC:basal cell carcinoma ratio (1.7:1) in comparison to general population. 10/64 (15.6%) of SCCs were “high risk” (Brigham Women Hospital T2b or higher). Peritumoral infiltrate was present on 12/82 (14.6%) of tumors with majority having some residual tumor present (75%). Peritumoral infiltrate appeared to be unique to individual patients which suggests that the infiltrate is attributable to patient or disease specific factors rather than an association with the tumor itself. Further studies to support this conclusion include a prospective study design to collect clinical, immunologic, and genetic data. None disclosed.